Rule2023-26206
Endangered and Threatened Wildlife and Plants; Threatened Species Status With Section 4(d) Rule for North American Wolverine
Primary source
Metadata and text below are from the Federal Register, a public-domain U.S. government work. Always verify the official published version before relying on it for any legal matter.
Published
November 30, 2023
Effective
January 2, 2024
Issuing agencies
Interior DepartmentFish and Wildlife Service
Abstract
We, the U.S. Fish and Wildlife Service (Service), determine threatened species status under the Endangered Species Act of 1973 (Act), as amended, for the distinct population segment (DPS) of the North American wolverine (Gulo gulo luscus) occurring in the contiguous United States. This rule adds the contiguous U.S. DPS of the North American wolverine to the Federal List of Endangered and Threatened Wildlife. We are also issuing an interim rule under the authority of section 4(d) of the Act (an "interim 4(d) rule") that provides the prohibitions, and exceptions to those prohibitions, necessary and advisable for the conservation of the contiguous U.S. DPS of the North American wolverine.
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[Federal Register Volume 88, Number 229 (Thursday, November 30, 2023)]
[Rules and Regulations]
[Pages 83726-83772]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2023-26206]
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Vol. 88
Thursday,
No. 229
November 30, 2023
Part IV
Department of the Interior
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Fish and Wildlife Service
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50 CFR Part 17
Endangered and Threatened Wildlife and Plants; Threatened Species
Status With Section 4(d) Rule for North American Wolverine; Final and
Interim Rule
Federal Register / Vol. 88 , No. 229 / Thursday, November 30, 2023 /
Rules and Regulations
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DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
[Docket No. FWS-R6-ES-2023-0216; FF09E21000 FXES11110900000 245]
RIN 1018-BH27
Endangered and Threatened Wildlife and Plants; Threatened Species
Status With Section 4(d) Rule for North American Wolverine
AGENCY: Fish and Wildlife Service, Interior.
ACTION: Final rule and interim rule with request for comments.
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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), determine
threatened species status under the Endangered Species Act of 1973
(Act), as amended, for the distinct population segment (DPS) of the
North American wolverine (Gulo gulo luscus) occurring in the contiguous
United States. This rule adds the contiguous U.S. DPS of the North
American wolverine to the Federal List of Endangered and Threatened
Wildlife. We are also issuing an interim rule under the authority of
section 4(d) of the Act (an ``interim 4(d) rule'') that provides the
prohibitions, and exceptions to those prohibitions, necessary and
advisable for the conservation of the contiguous U.S. DPS of the North
American wolverine.
DATES:
Effective date: This rule is effective January 2, 2024.
Comments due: Comments on the interim 4(d) rule must be received or
postmarked by January 29, 2024.
ADDRESSES:
Written comments on the interim 4(d) rule: You may submit comments
on the interim 4(d) rule by one of the following methods:
(1) Electronically: Go to the Federal eRulemaking Portal: <a href="https://www.regulations.gov">https://www.regulations.gov</a>. In the Search box, enter FWS-R6-ES-2023-0216,
which is the docket number for this rulemaking. Then click on the
Search button. On the resulting page, in the panel on the left side of
the screen, under the Document Type heading, click on the Rules box to
locate this document. You may submit a comment by clicking on
``Comment.''
(2) By hard copy: U.S. mail: Public Comments Processing, Attn: FWS-
R6-ES-2023-0216; U.S. Fish and Wildlife Service; MS: PRB/3W; 5275
Leesburg Pike; Falls Church, VA 22041-3803.
We will post all comments on <a href="https://www.regulations.gov">https://www.regulations.gov</a>. This
generally means that we will post any personal information you provide
us (see Public Comments Solicited on the Interim 4(d) Rule, below, for
more information).
Availability of supporting materials: This document is available on
the internet at <a href="https://www.regulations.gov">https://www.regulations.gov</a> and at <a href="https://ecos.fws.gov/ecp/species/5123">https://ecos.fws.gov/ecp/species/5123</a>. Supporting materials we used in
preparing this rule, including the 2018 species status assessment (SSA)
report and the 2023 addendum to the SSA report, are available on the
Service's website at <a href="https://ecos.fws.gov/ecp/species/5123">https://ecos.fws.gov/ecp/species/5123</a>, at <a href="https://www.regulations.gov">https://www.regulations.gov</a> at Docket No. FWS-R6-ES-2023-0216, or both.
FOR FURTHER INFORMATION CONTACT: Jodi Bush, U.S. Fish and Wildlife
Service, Pacific Region, 911 NE 11th Ave., Portland, OR 97232;
telephone: (503) 231-6131. Individuals in the United States who are
deaf, deafblind, hard of hearing, or have a speech disability may dial
711 (TTY, TDD, or TeleBraille) to access telecommunications relay
services. Individuals outside the United States should use the relay
services offered within their country to make international calls to
the point-of-contact in the United States.
SUPPLEMENTARY INFORMATION:
Executive Summary
Final Rule To List the Contiguous U.S. DPS of the North American
Wolverine
Why we need to publish a rule. The Act (16 U.S.C. 1531 et seq.)
defines ``species'' as any subspecies of fish or wildlife or plants,
and any distinct population segment (DPS) of any species of vertebrate
fish or wildlife which interbreeds when mature. Under the Act, a
species warrants listing if it meets the definition of an endangered
species (in danger of extinction throughout all or a significant
portion of its range) or a threatened species (likely to become an
endangered species within the foreseeable future throughout all or a
significant portion of its range). If we determine that a species
warrants listing, we must list the species promptly and designate the
species' critical habitat to the maximum extent prudent and
determinable. We have determined that the DPS of the North American
wolverine occurring in the contiguous United States (the ``contiguous
U.S. DPS'') meets the Act's definition of a threatened species;
therefore, we are listing it as such. Listing a species as an
endangered or threatened species can be completed only by issuing a
rule through the Administrative Procedure Act rulemaking process (5
U.S.C. 551 et seq.).
What this document does. This document is both (1) a final rule
listing the contiguous U.S. DPS of the North American wolverine as a
threatened species under the Act; and (2) an interim rule issued under
the authority of section 4(d) of the Act (an ``interim 4(d) rule'')
providing the prohibitions, and exceptions to those prohibitions, that
are necessary and advisable to provide for the conservation of the
contiguous U.S. DPS of the North American wolverine.
The basis for our action. Under the Act, we may determine that a
species is an endangered or threatened species because of any of five
factors: (A) The present or threatened destruction, modification, or
curtailment of its habitat or range; (B) overutilization for
commercial, recreational, scientific, or educational purposes; (C)
disease or predation; (D) the inadequacy of existing regulatory
mechanisms; or (E) other natural or manmade factors affecting its
continued existence. We have determined that the contiguous U.S. DPS of
the North American wolverine is a threatened species due primarily to
the ongoing and increasing impacts of climate change and associated
habitat degradation and fragmentation.
Section 4(a)(3) of the Act requires the Secretary of the Interior
(Secretary) to designate critical habitat concurrent with listing to
the maximum extent prudent and determinable. We have not yet obtained
the necessary economic information needed to develop a proposed
critical habitat designation for the contiguous U.S. DPS of the North
American wolverine. Therefore, we find that designation of critical
habitat for the DPS is currently not determinable.
Interim 4(d) Rule
The need for the regulatory action and how the action will meet
that need. Consistent with section 4(d) of the Act, this interim 4(d)
rule provides measures that are tailored to our current understanding
of the conservation needs of the North American wolverine.
Under section 4(d) of the Act, the Secretary of the Interior has
discretion to issue such regulations as she deems necessary and
advisable to provide for the conservation of the species. The Secretary
also has the discretion to prohibit by regulation with respect to a
threatened species, any act prohibited by section 9(a)(1) of the Act.
Summary of the major provisions of the regulatory action. This
interim 4(d) rule will provide for the conservation of the contiguous
U.S. DPS of the North American wolverine by prohibiting the following
activities, unless they fall
[[Page 83727]]
within the specific identified exceptions or are otherwise authorized
or permitted: importing or exporting; take; possession and other acts
with unlawfully taken specimens; delivering, receiving, carrying,
transporting, or shipping in interstate or foreign commerce in the
course of commercial activity; or selling or offering for sale in
interstate or foreign commerce.
The interim 4(d) rule will also provide for the conservation of the
species by allowing exceptions to the general prohibitions against
``take'' of the species in support of conservation actions and
otherwise lawful activities that could take wolverines but at minimal
levels not likely to have a negative impact on the species'
conservation. The exceptions include take due to scientific research
conducted on wolverines by a Federal or Tribal biologist in the course
of their official duties, incidental take resulting from forest
management activities for the purposes of reducing the risk or severity
of wildfire, and incidental take resulting from legal trapping
conducted consistent with State and Tribal trapping rules or guidelines
that contain steps to minimize the potential for capture of wolverine.
Supporting Documents
A team prepared a species status assessment (SSA) for the North
American wolverine (Gulo gulo luscus) (Service 2018, entire) (hereafter
referred to as the wolverine SSA report). The SSA team was composed of
U.S. Fish and Wildlife Service (Service) biologists, who consulted with
other species experts. The wolverine SSA report represented a
compilation of the best scientific and commercial data available (known
at that time) concerning the status of the North American wolverine,
including the impacts of past, present, and future factors (both
negative and beneficial) affecting the wolverine. The wolverine SSA
report underwent independent peer review by scientists with experience
with mesocarnivores and their conservation and management, genetics,
population modeling, and climate change.
More recently, the Service prepared an SSA addendum for the North
American wolverine (Gulo gulo luscus) (Service 2023, entire) (hereafter
referred to as the wolverine SSA report addendum). The wolverine SSA
report addendum contains a synthesis of relevant new information that
has become available since the 2018 wolverine SSA report. The wolverine
SSA report addendum underwent independent peer review by scientists
with experience with mesocarnivores and their conservation and
management, genetics, population modeling, and climate change. The
wolverine SSA report addendum also underwent technical review by State,
Federal, and Tribal biologists.
The wolverine SSA report, the wolverine SSA report addendum, and
other materials relating to this rulemaking can be found at the
Service's website at <a href="https://ecos.fws.gov/ecp/species/5123">https://ecos.fws.gov/ecp/species/5123</a>, and at
<a href="https://www.regulations.gov">https://www.regulations.gov</a> at Docket No. FWS-R6-ES-2023-0216.
Previous Federal Actions
On February 4, 2013, we published in the Federal Register (78 FR
7864) a proposed rule to list the DPS of the North American wolverine
occurring in the contiguous United States as a threatened species under
the Act, with a proposed rule under section 4(d) of the Act that
outlined the prohibitions, and exceptions to those prohibitions,
necessary and advisable for the conservation of the wolverine. Please
refer to that February 4, 2013, proposed rule (78 FR 7864) for a
detailed description of previous Federal actions concerning the
wolverine prior to 2013. We published a separate proposed rule in the
Federal Register on February 4, 2013 (78 FR 7890), to establish a
nonessential experimental population (NEP) area for the North American
wolverine in the Southern Rocky Mountains of Colorado, northern New
Mexico, and southern Wyoming. On October 31, 2013, we reopened the
comment period on the proposed listing rule for an additional 30 days
(78 FR 65248).
Following publication of the 2013 proposed rules, there was
scientific disagreement and debate about the interpretation of the
habitat requirements for wolverines and available climate change
information used to determine the extent of threats to the contiguous
U.S. DPS of the North American wolverine. Based on this substantial
disagreement regarding the sufficiency or accuracy of the available
data relevant to the proposed listing, on February 5, 2014, we
announced in the Federal Register (79 FR 6874) a 6-month extension of
the final determination of whether to list the contiguous U.S. DPS of
North American wolverine as a threatened species under the Act. That
document reopened the comment period on the February 4, 2013, proposed
listing rule for an additional 90 days.
On August 13, 2014, we published in the Federal Register (79 FR
47522) a document withdrawing both proposed rules published on February
4, 2013: (1) the proposed rule to list the contiguous U.S. DPS of the
North American wolverine as a threatened species under the Act,
including the provisions proposed under section 4(d) of the Act; and
(2) the proposed NEP designation under section 10(j) of the Act for the
North American wolverine in the Southern Rocky Mountains of Colorado,
northern New Mexico, and southern Wyoming. These withdrawals were based
on our conclusion that the factors affecting the DPS as identified in
the listing proposed rule were not as significant as believed at the
time of that proposed rule's publication in 2013.
In October 2014, three complaints were filed in the District Court
for the District of Montana by Defenders of Wildlife, WildEarth
Guardians, Center for Biological Diversity, and other organizations
challenging the withdrawal of the February 4, 2013, proposed rule to
list the contiguous U.S. DPS of the North American wolverine. Numerous
parties intervened in the litigation. These three cases were
consolidated, and on April 4, 2016, the court issued a decision. The
court granted plaintiffs' motion for summary judgment with respect to
the Service's determination regarding (1) the threat posed to the
wolverine by the effects of climate change at the reproductive denning
scale, (2) the threat posed to the wolverine by small population size
and lack of genetic diversity, and (3) the application of the
significant portion of the range policy to the wolverine. As a result
of the court order, the August 13, 2014, withdrawal (79 FR 47522) of
the February 4, 2013, proposed listing rule was vacated and remanded to
the Service for further consideration consistent with the order.
In effect, the court's action returned the process to the proposed
rule stage, and the status of the contiguous U.S. DPS of the North
American wolverine under the Act reverted to that of a proposed species
for the purposes of consultation under section 7 of the Act. On October
18, 2016, we published in the Federal Register (81 FR 71670) a document
reopening the comment period on the February 4, 2013, proposed rule to
list the DPS of the North American wolverine occurring in the
contiguous United States as threatened under the Act (78 FR 7864). The
October 18, 2016, publication also requested new information and
announced that we were initiating a new and comprehensive status review
of the North American wolverine, to determine whether the species meets
the definition of an endangered or threatened species under the Act, or
[[Page 83728]]
whether the species is not warranted for listing. Both new and updated
information and analyses presented in the wolverine 2018 SSA report,
along with public comments, prompted us to reevaluate our previous
assessment of the DPS (presented in our 2013 proposed listing rule (78
FR 7864), which in turn relied on the DPS analysis completed in our
2010 12-month finding (75 FR 78030)) with respect to the North American
wolverine in the contiguous United States.
On October 13, 2020, we published in the Federal Register (85 FR
64618) another document withdrawing the February 4, 2013, proposed rule
to list the DPS of the North American wolverine occurring in the
contiguous United States as threatened under the Act. Our 2020
withdrawal decision was based on our conclusion that the factors
affecting the North American wolverine occurring in the contiguous
United States as identified in the 2013 proposed listing rule were not
as significant as believed at the time of the proposed rule's
publication in 2013. We also found that the North American wolverines
occurring in the contiguous United States did not qualify as a DPS.
The Center for Biological Diversity and WildEarth Guardians filed
lawsuits in the District Court for the District of Montana challenging
the Service's 2020 decision to withdraw the February 4, 2013, proposal
to list the contiguous U.S. DPS of the North American wolverine. The
cases were consolidated, and the State of Idaho's motion to intervene
was granted. On February 4, 2022, the Service filed a motion asking the
court to voluntarily return (remand) the 2020 withdrawal decision to
the Service to allow the Service to re-examine the decision in light of
the intervening decision in Center for Biological Diversity v. Haaland,
998 F.3d 1061 (9th Cir. 2021) (``Pacific Walrus Decision'') and to
reevaluate the decision in light of new scientific information that had
become available since the completion of the 2018 SSA. The Service also
requested that the 2020 withdrawal decision remain in effect pending
that reevaluation. On May 26, 2022, the court granted the Service's
request for a voluntary remand of the 2020 withdrawal decision, but the
court decided to vacate the withdrawal decision (Ctr. for Biological
Diversity v. Haaland, No. CV 20-181-M-DWM (D. Mont. May 26, 2022)).
The court's May 26, 2022, action returned the listing process for
the North American wolverine to the proposed rule stage. On November
23, 2022, the Service published in the Federal Register (87 FR 71557) a
document soliciting new information on the North American wolverine and
notifying the public that the February 4, 2013, proposed rule to list
the contiguous U.S. DPS of the North American wolverine as threatened
under the Act (78 FR 7864) had been reinstated. As of May 26, 2022, for
purposes of consultation under section 7 of the Act, the North American
wolverine was again a species proposed for listing and subject to
conferencing requirements.
The Service then completed the wolverine SSA report addendum
(Service 2023, entire), which contains a synthesis of all relevant new
information that has become available since the 2018 wolverine SSA
report to inform this final listing rule and the associated interim
4(d) rule.
Peer Review
Our assessment of the status of the North American wolverine
contained in this document is supported by information in both the 2018
SSA report (Service 2018, entire) and the 2023 wolverine SSA report
addendum (Service 2023, entire). In accordance with our joint policy on
peer review published in the Federal Register on July 1, 1994 (59 FR
34270), and our August 22, 2016, memorandum updating and clarifying the
role of peer review in listing actions under the Act, we solicited
independent scientific review of the information contained in the 2018
wolverine SSA report. We sent the SSA report to four independent peer
reviewers and received four responses; we incorporated the results of
that review into the SSA report, as appropriate. More recently, we
solicited independent scientific review of the 2023 wolverine SSA
report addendum. We sent the wolverine SSA report addendum to six peer
reviewers and received three responses; we incorporated the results of
the peer review into the wolverine SSA report addendum, as appropriate.
The peer reviews on the wolverine SSA report and the wolverine SSA
report addendum can be found at <a href="https://www.regulations.gov">https://www.regulations.gov</a>.
Summary of Changes
Since the publication of the February 4, 2013, proposed listing
rule (78 FR 7864), the development of the 2018 SSA report (Service
2018, entire), and the publication of the October 13, 2020, withdrawal
document (85 FR 64618), a substantial number of new studies have become
available, refining our understanding of wolverine biology and threats
affecting North American wolverines in the contiguous United States. We
incorporated this new information into the 2023 wolverine SSA report
addendum. We summarize the information most salient to our
determination in this final rule below. We also discuss these changes
where appropriate in the remainder of the document to provide further
detail and context.
Ecological Requirements
The snow model used in the climate change analysis in the 2018 SSA
report and October 13, 2020, withdrawal document (85 FR 64618)
projected snow loss out to year 2050 in only two modeling domains
(Glacier National Park and the central Rocky Mountains) (Service 2018,
p. 88). Results indicated a decline in spring snow in these areas due
to climate change was likely, but we were unable to extrapolate those
projections across the remainder of the North American wolverine's
breeding range in the contiguous United States. Persistent spring snow
(greater than or equal to 1 meter on May 1; see Climate Change, below)
was not identified as an ecological requirement for wolverines, and we
assumed that if snow was necessary for denning, there would be enough
spring snowpack in the future to fulfill denning needs.
Our updated climate analysis reported in the 2023 wolverine SSA
report addendum projects snow loss out to 2100 across five modeling
domains that cover a much larger extent of the breeding range in the
contiguous United States when compared to the 2018 SSA report. In our
2023 wolverine SSA report addendum, we found declines in spring snow
due to climate change are likely across the North American wolverine's
range and predicted losses will be greater in 2100 than in 2050. In
general, when compared to historical amounts of snow cover, nearly
every area modeled (except for the Mid-Rockies) sees a decrease in snow
cover and that decrease becomes larger over time. In the Mid-Rockies,
snow cover increases in the short term, but as with the other areas, it
decreases over time.
New research indicates that areas characterized by persistent
spring snow are likely important for wolverine survival (e.g., caching
food) in addition to denning and reproduction. One new study reported
wolverines cache food year-round, indicating that warmer temperatures
could impact the ability of wolverines to store food resources by
decreasing the shelf-life (usability) of cached food, and increasing
competition from pilferers that benefit from a warmer climate (van der
Veen et al. 2020, p. 1). Another study found evidence to support a
functional
[[Page 83729]]
relationship between North American wolverines and persistent spring
snow that could be explained by the distribution of food, disturbance,
or mortality risk (Kortello et al. 2019, p. 8).
Connectivity With Canada
Connectivity with Canada is essential to the long-term viability of
North American wolverines in the contiguous United States (Cegelski et
al. 2006, p. 209). In the 2018 SSA report and October 13, 2020,
withdrawal document (85 FR 64618), we assumed that wolverines could
move freely between Canada and the United States (Service 2018, p.
104). We also concluded that trapping of wolverines did not represent a
barrier to wolverine movement and dispersal along the international
border (Service 2018, p. 69). Additionally, we concluded that major
highways did not represent a barrier to wolverine movement (Service
2018, p. 60).
In the 2023 wolverine SSA report addendum, we affirm that
connectivity with Canada is essential to the long-term viability of
North American wolverines in the lower 48 States. However, our
understanding of the ability of wolverines to move between Canada and
the United States in the Rocky Mountains has changed. New research
found an estimated 41 percent decline in the wolverine population from
2011-2020 in a portion (7,583,417 acres (ac) (30,689 square kilometers
(km\2\))) of the southern Canadian Rockies, Purcell Mountains, and
Selkirk Mountains important for wolverine connectivity with the United
States; this decline could be attributed to one or more of the
following causes: trapping, backcountry recreation, human development,
and food availability (Barrueto et al. 2022, p. 4). In addition, new
transboundary genetic research indicates the Trans-Canada Highway in
southern British Columbia is impeding female dispersal from Canada to
the United States, thereby limiting gene flow and the ability of
dispersing wolverines to supplement the contiguous U.S. DPS (Sawaya et
al. 2023, pp. 12, 17).
Genetic Diversity and Adaptive Capacity
In the October 13, 2020, withdrawal document (85 FR 64618), we
found there was no available information to indicate that the current
abundance of the North American wolverine across its range in the
contiguous United States was at a level that was causing inbreeding
depression or loss of genetic variation that would affect its ability
to adapt to changing conditions.
New transboundary genetic research shows a sharp decline in genetic
diversity and increasing population fragmentation at the southern
extent of the North American wolverine's range in western North America
(Sawaya et al. 2023, p. 17). As a result, there is potential for
inbreeding given the relatively small population sizes and low levels
of genetic diversity of wolverines in the contiguous United States,
especially in the Cascade Mountains of Washington and southern British
Columbia (Sawaya 2023, pers. comm.); however, inbreeding depression has
not been observed. New analysis of the North American wolverine's
adaptive capacity shows that their specialized habitat associations,
low genetic diversity and population size, narrow ecological niche, low
tolerance for human disturbance, and slow reproductive rate all
contribute to the wolverine's relative difficulty in adapting in-place
to future environmental change (Service 2023, p. 66).
Roads and Development
We analyzed the effects of roads and development (human
disturbance) to North American wolverines in the 2018 SSA report
(Service 2018, p. 62) and determined in our October 13, 2020,
withdrawal document (85 FR 64618) that impacts to wolverines are small
and narrow in scope and scale. We did not consider roads and
development to be an impediment to wolverine movement and gene flow.
New habitat and landscape genetic research indicates multi-lane
roads and human development in valley bottoms between core habitats may
limit dispersal and population connectivity to some extent, especially
for female wolverines. Connectivity among wolverine habitats appears to
be particularly sensitive to housing developments (Balkenhol et al.
2020, p. 797). Also, new research indicates that human disturbance
(road density) and food availability are major drivers of wolverine
distribution in winter (Kortello et al. 2019, p. 1). Wolverine density
and detection probability declined in areas with more human development
(Barrueto et al. 2022, p. 4). Human development may also have cascading
impacts of increasing competition from other mesocarnivores that are
less affected by human disturbance (Frey et al. 2020, pp. 1136-1138;
Chow-Fraser et al. 2022, p. 6; Milanesi et al. 2022, pp. 10-11).
Winter Recreation
In our 2018 SSA report and October 13, 2020, withdrawal document
(85 FR 64618), we concluded that winter recreation is a low-level
stressor for wolverines in the contiguous United States (Service 2018,
p. 62). The limited research available at the time indicated some
avoidance behavior exhibited by wolverines in areas with backcountry
winter recreation, but not to the extent that we had concerns about
population-level impacts.
In the 2023 wolverine SSA report addendum, we provide an updated
assessment of the effects of winter recreation based on new studies.
Research indicates winter recreation is negatively associated with
North American wolverine habitat use, and that winter recreation is
likely to increase and become more concentrated in the future as snow-
covered areas decline due to climate change (Heinemeyer et al. 2019, p.
1). A large multi-State analysis of winter recreation impacts in the
Northern Rocky Mountains was published in 2019, indicating greater
concern for impacts to wolverines than we found in 2018 and showing a
negative functional response to the level of recreation exposure within
their home ranges (Heinemeyer et al. 2019a, pp. 13-14, 17-18).
Additionally, new research found an incremental loss of wolverines in
portions of central Idaho where winter recreation impacts are
increasing (Mack and Hagan 2022, p. 13). Furthermore, forest roads used
by snowmobilers in the Canadian Rockies were found to have a strong
negative correlation with wolverine distribution (Kortello et al. 2019,
p. 10). Wolverine detection probability in protected and non-protected
habitat of southwestern Canada was found to be strongly and negatively
correlated with nonmotorized recreation in summer and winter (Barrueto
et al. 2022, p. 5).
Trapping
In our 2018 SSA and the October 13, 2020, withdrawal document (85
FR 64618), we concluded that overutilization does not currently
represent a stressor to the North American wolverine in the contiguous
United States at the individual, population, or species level. We also
concluded that trapping in Canada has been and appears to be
sustainable, and trapping or harvesting of wolverines along the
contiguous U.S.-Canada border does not represent a stressor to
wolverines migrating into the contiguous United States and does not
represent a barrier to wolverine movement and dispersal along the
international border (Service 2018, p. 71).
Legal trapping of wolverines has not occurred in the contiguous
United States in the past 10 years, and lethal
[[Page 83730]]
incidental trapping of wolverines has been minimal (Service 2023, p.
38). We expect recent changes to wolf trapping regulations in Idaho and
Montana to have little effect on wolverines at a population level, as
long as trapping is done in a manner to limit wolverine bycatch (Idaho
Department of Fish and Game (IDFG) 2023, in litt., p. 1; IDFG 2022, p.
40; Montana Fish, Wildlife and Parks (MFWP) 2023, in litt., p. 1; MFWP
2022, entire). Below, under Overutilization for Commercial,
Recreational, Scientific, or Educational Purposes, we provide an
assessment of incidental trapping and the measures States are taking to
reduce incidental trapping of wolverines.
Recent research on wolverine trapping in Southern Canada indicates
that trapping may be having more of a negative effect on wolverine
populations in Canada than previously thought (Kortello et al. 2019,
pp. 1, 10; Mowat et al. 2020, entire; Barrueto et al. 2020, p. 296;
Barrueto et al. 2022, entire). Unsustainable trapping levels in Canada
could limit dispersal of individuals into the contiguous United States,
where the dispersal of wolverines from Southern Canada is vital to the
genetic and demographic health of the U.S. population (Sawaya 2023,
pers. comm.).
Summary of Comments and Recommendations
Comments on the 2013 Proposed Listing Rule
Upon publication of our February 4, 2013, proposed rule to list the
DPS of North American wolverine occurring in the contiguous United
States as a threatened species (78 FR 7864), we opened a 90-day public
comment period, ending May 6, 2013. After we withdrew the proposed
rule, on October 18, 2016 (81 FR 71670), we again opened a public
comment period on our 2013 proposed listing rule; that comment period
was open for 30 days, ending November 17, 2016. At both times, we
contacted appropriate Federal and State agencies, scientific experts
and organizations, Tribes, and other interested parties and invited
them to comment on the 2013 proposed listing rule. Many of the comments
we received from State agencies during our 2016 reopened comment period
(81 FR 71670) were similar to those we received during the initial 2013
public comment period (78 FR 7864). All substantive information
provided during both comment periods on our 2013 proposed listing rule
has either been incorporated directly into this final determination or
is addressed below.
Below, we present the comments received on the 2013 proposed
listing rule and a summary of our responses as presented in the October
13, 2020, withdrawal document (85 FR 64618). We also provide updated
responses to several of the comments based on new information presented
in the 2023 wolverine SSA report addendum and this final rule. Comments
are numbered below as they were numbered in the October 13, 2020,
withdrawal document (85 FR 64618). Several of the comments and
responses from the October 13, 2020, withdrawal document did not
require revision, and they are incorporated here by reference; those
comments with responses that remain the same are comments 6, 7, 9, 11,
13, 20, 21, 22, 23, and 24 (85 FR 64618 at 64622-64626).
Public Comments
(1) Comment: We received several public comments claiming that the
North American wolverine faces increasing threats from the effects of
climate change, particularly habitat loss due to declining snowpack.
Our 2020 Response Summarized: Our climate assessment in the 2018
wolverine SSA report and October 13, 2020, withdrawal document focused
on the impact of climate change to denning conditions for wolverines.
We stated we recognize that current climate trends and future (2055 and
later) climate model projections indicate warming temperatures for much
of western North America and changes to snow-pack conditions. In
general, models indicate higher elevations, where documented historical
wolverine denning has occurred, will retain more snow cover than lower
elevations, particularly in early spring (on April 30/May 1). We
referenced a climate analysis that included two regions, Glacier
National Park and Rocky Mountain National Park. Details of this climate
analysis are presented in Ray et al. (2017) and are summarized in the
2018 SSA report. Climate models in Ray et al. (2017) built upon
previous model projections presented in McKelvey et al. (2011), but
with significant differences such as finer spatial resolution,
incorporation of slope and aspect, snow depth estimates, additional
years of historical data, and wider temporal analyses of snow
persistence (April-June). Model projections from Ray et al. (2017)
indicate significant areas (several hundred square kilometers (km\2\)/
square miles (mi\2\) for each study area) of future snow (greater than
0.5 meters (m) (20 inches (in)) in depth) are likely to persist on May
1 at elevations currently used by wolverines for denning. This is true,
on average, across the range of climate models used out to
approximately year 2055.
Our 2023 Response: Our assessment of climate change impacts to
North American wolverines in the 2023 wolverine SSA report addendum,
and applied in this final rule, evaluates the impact of climate warming
and changes in snowpack on various aspects of wolverine ecology, not
just denning habitat (see Climate Change, below). We now consider
habitats characterized by the presence of persistent spring snow for
survival and reproduction to be a physical and ecological requirement
for wolverines in the contiguous United States (see Life-History Needs,
below). New evidence from around the world reinforces that snow--
especially persistent spring snow--is an important predictor of broad-
scale wolverine distribution and density (Aubry et al. 2023, pp. 15-16;
Carroll et al. 2020, p. 8; Fisher et al. 2022, p. 10; Glass et al.
2021, entire; Mowat et al. 2020, p. 220). Snow cover appears to
influence wolverine dispersal and resulting genetic structure
(Balkenhol et al. 2020, pp. 798-799). Warming future conditions could
make caching food more difficult for wolverines year-round (Van der
Veen et al. 2020, pp. 8-10). Climate change also has the potential to
exacerbate the impacts of other stressors, including effects from
roads, winter recreational activity, development, low genetic
diversity, and small populations (see Threats, below). Wolverines have
denned outside of spring snowpack in the boreal forests of Canada and
Scandinavia; however, the importance of spring snow for denning may
vary among areas depending on the abundance of alternative den site
structures, competitors, and food resources (Persson et al. 2023, p.
5810). Furthermore, there is no evidence that North American wolverines
have denned in areas outside of spring snowpack in their alpine
habitats in the contiguous United States. In light of this, we do not
expect North American wolverines to continue to have the same or better
resiliency in the contiguous United States in the future when cold and
snowy conditions are expected to decrease, with spring snowpack
decreasing as much as 50 percent in some areas. Although we are not
seeing deleterious effects of climate change on the contiguous U.S.
population of North American wolverines currently, we expect future
impacts at the population level. For further detail, see the discussion
under Climate Change, below.
(2) Comment: We received several public comments during our request
for
[[Page 83731]]
information claiming that low population size (and small effective
population size) warrant listing of the North American wolverine as
threatened or endangered.
Our 2020 Response Summarized: We stated that wolverines are
difficult animals to survey, and populations occur in naturally low
densities across their North American range, due in large part to their
need for large, exclusive territories. At that time (and still today),
the only estimate of the number of wolverines that currently occupy the
contiguous United States is the often-cited population estimate of 318
wolverines (range: 249-926) in the contiguous United States. This
estimate was derived from habitat modeling presented in Inman et al.
(2013). That publication also provided a modeled estimate of potential
wolverine capacity in the contiguous United States of 644 wolverines
(range: 506-1881). We also reported the preliminary results from the
Western States Wolverine Conservation Project (WSWCP) occupancy study
in four western States (Idaho, Montana, Washington, and Wyoming) and
from a pilot occupancy study in Wyoming (2015-2016) (Service 2018,
appendix B). Preliminary analysis of the study results indicated an
average estimated probability of occupancy of 0.42, suggesting that
wolverines used nearly half of all sites during the study period (MFWP
2017, pers. comm.). Although the sum of these reports cannot confirm
the previous estimate of population size or verify population trends,
they offer recent evidence that wolverines continue to be observed
across a large area of the western United States.
We also discussed the estimated effective population size by
Schwartz et al. (2009), which estimated a summed effective population
size of 35, with credible limits from 28 to 52 (Schwartz et al. 2009,
p. 3,226). We stated that the analysis missed two wolverine
subpopulations as well as individuals, which would underestimate the
results for this type of analysis. We went on to discuss the apparent
connectivity between wolverines in the contiguous United States and
Canada, and we considered the contiguous United States to be
genetically continuous with wolverines in adjacent Canadian provinces.
We concluded that a small effective population size would be more of a
concern if the population was in isolation; however, wolverines in the
contiguous United States are not genetically isolated from wolverines
in Canada.
Our 2023 Response: The best available estimate of effective
population size for the wolverine in the Northern Rocky Mountains
continues to be 35 (credible interval = 28-52) (Schwartz et al. 2009,
p. 3226). We estimated the effective population size of wolverines in
the North Cascades to be four (Service 2023, p. 27). Overall, the
effective population size estimates of wolverines in the contiguous
United States are small compared to conservation guidelines, and the
contiguous U.S. DPS of North American wolverines appear to be
vulnerable to inbreeding and loss of genetic diversity when considered
in isolation. However, only one or two effective migrants per
generation (i.e., the number of migrants that reproduce at the same
rate as residents) are likely needed to achieve genetic population
connectivity and maintain existing levels of genetic diversity
(Cegelski et al. 2006, p. 209).
At the time we published the October 13, 2020, withdrawal document
(85 FR 64618), we considered the contiguous U.S. population to be
genetically continuous with Canada. We now know that wolverine
populations in southern British Columbia and Alberta near the
transboundary interface are less genetically connected to the
contiguous United States than we found in our 2018 SSA. New information
has revealed that female wolverines appear to avoid crossing major
roadways, including the Trans-Canada Highway (Highway 1) and the
Crowsnest Highway (Highway 3) in southern British Columbia (Sawaya et
al. 2023, pp. 11-14). Substantially lower mitochondrial DNA diversity
in the United States, as compared to mitochondrial DNA diversity in
Canada, is consistent with the nuclear DNA signals of limited
contemporary female gene flow between the countries and the wolverine's
relatively recent recolonization at the southern edge of their range
(Sawaya et al. 2023, p. 17). See ``Gene Flow Between the United States
and Canada'' and ``Population Structure and Gene Flow Within Canada,''
below, for more detail. Given the new information on limited gene flow
with Canada and the potential impacts of climate change to future
dispersal, the low effective population size in the contiguous U.S.
population of North American wolverines is a concern to future
population viability.
(3) Comment: We received several public comments during our request
for information claiming that the North American wolverine faces
threats from indiscriminate trapping in the contiguous United States,
or are negatively impacted by incidental trapping.
Our 2020 Response Summarized: In our October 13, 2020, withdrawal
document (85 FR 64618), we stated that trapping or hunting of
wolverines was not allowed in any State within the range of the
wolverine in the contiguous United States, and we presented the legal
protections afforded to wolverines in each State. We summarized what we
knew at the time about incidental trapping. In the wolverine SSA
report, we provided a summary of the number of wolverines that have
been incidentally trapped in Idaho (18 since 1965, including 6 known to
be released alive and 7 known mortalities), Montana (4 since 2013, 3
mortalities and 1 released unharmed), and Wyoming (2 since 1996, 1
mortality and 1 released unharmed) (Service 2018, p. 66). Both Idaho
and Montana are implementing trapper education programs to minimize
nontarget wolverine captures. We noted that regulated trapping and
hunting of wolverines occurs in parts of Alaska and Canada, and appears
to be sustainable based on population and density estimates.
Our 2023 Response: Legal trapping of wolverines has not occurred in
the contiguous United States in the past 10 years. Wolverine trapping
remains closed throughout the western United States, and wolverines
have retained various protected status designations in the States
within their current U.S. range (Service 2023, table 10). Therefore,
legal direct trapping is no longer a stressor on wolverines in the
contiguous United States. In the past 10 years, lethal incidental
trapping of wolverines has been minimal (approximately 1 to 2 animals
per year or fewer), primarily occurring in Idaho and Montana (see
Overutilization for Commercial, Recreational, Scientific, or
Educational Purposes, below). New information suggests that recent
overharvest from trapping has occurred in southern Canada in areas that
could provide dispersing individuals to the contiguous United States
(Mowat et al. 2020, entire). Trapping in southern Canada appears to
have had a more negative effect on wolverine populations in Canada than
previously thought. Legacy effects of recent unsustainable trapping
levels in a portion of the southern Rocky Mountains of Canada could
limit dispersal of individuals into the contiguous United States in an
area where wolverine connectivity between the United States and
southern Canada is vital to the genetic and demographic health of the
U.S. wolverine population. See Overutilization for Commercial,
Recreational, Scientific, or Educational Purposes and Provisions of the
Interim 4(d) Rule, below, for further details.
[[Page 83732]]
(4) Comment: We received several public comments identifying
potential threats to wolverines from winter recreation activities, such
as snowmobiling and backcountry skiing.
Our 2020 Response Summarized: When we published our October 13,
2020, withdrawal document (85 FR 64618), there was little information
on the effect of winter recreation on wolverines. We received a final
report of a multiyear study on the effects of winter recreation on
wolverines (Heinemeyer et al. 2017, entire) in mid-December 2017, and
the results of this study were published (Heinemeyer et al. 2019a,
entire) prior to the publication of our 2020 withdrawal document. The
study found that wolverines were displaced from habitat by winter
recreation but maintained multiyear home ranges, and the authors
suggest that wolverines are able to tolerate winter recreation at some
scales (Heinemeyer et al. 2017, p. iv; Heinemeyer et al. 2019a, p. 16).
The study described habitat selection as complex for female wolverines
and stated that habitat selection was likely driven by a combination of
abiotic (snow, cold) and biotic (predator avoidance, food availability)
factors (Heinemeyer et al. 2017, p. 36; Heinemeyer et al. 2019a, p.
16). This study did not assess demographic effects, fitness effects, or
population-level effects of winter recreation on wolverines (Heinemeyer
et al. 2019a, pp. 17, 19).
Our 2023 Response: There are multiple recent studies that indicate
wolverines are negatively affected and displaced (at least temporarily)
by various types of backcountry winter recreation (Barrueto et al.
2022, entire; Heinemeyer et al. 2019a, entire; Heinemeyer et al. 2019b,
entire; Kortello et al. 2019, entire; Mack and Hagen 2022, entire;
Regan et al. 2020, entire). The effect of winter recreation activity
(of concern due to potential impacts to denning and survival), in
isolation, represents a low threat to wolverines in the contiguous
United States at the population level. However, in combination with
other threats, including decreased snow availability (see Climate
Change, below) and increased overlap with winter recreationalists in
the future due to climate change, winter recreation could negatively
affect wolverine population resilience in the future. See Disturbance
Due to Winter Recreational Activity, below, for further details.
(5) Comment: We received public comments claiming that wolverines
are dependent on deep snow for survival and expressing concern for
future changes in snowpack due to the effects of climate change.
Our 2020 Response Summarized: Our response to this comment in our
October 13, 2020, withdrawal document (85 FR 64618) focused on snow
availability for denning and the wolverine's ability to cope with
changing snow conditions in the denning context. We stated that
wolverines can and have denned outside of heavy snowpack, multiple
factors play a role in den site selection, females will move dens as
young become mobile, and areas of significant snowpack will likely
persist in the future the contiguous United States in areas where
wolverines are known to den at levels that will continue to support
wolverines. Our review of studies of wolverine denning activity found
no quantitative data reporting snow depth at the den site when
wolverines abandon the den. More importantly, wolverine reproductive
success has not been studied relative to a number of abiotic and biotic
conditions, including depth and temporal aspect of spring snow cover.
In our evaluation of the effects of climate change to snowpack (see
Service 2018, pp. 73-99), we presented a finer-scale analysis (0.0625
km\2\ (0.24 mi\2\)) for two study areas (Glacier National Park and
Rocky Mountain National Park) that focused directly on May 15, in
addition to the presence or absence of snow on May 1 and April 15.
These dates are more relevant to the North America wolverine's life-
history needs. We also modeled the depth of ``significant'' snow (0.5 m
(20 in)) on these dates. We found that large areas (several hundred
km\2\/mi\2\ for each study area) of future snow cover (greater than 0.5
m (20 in) in depth) are projected to persist on May 1 at elevations
currently used by wolverines for denning. This is true, on average,
across the range of climate models used out to approximately year 2055.
Our 2023 Response: As discussed above in our response to (1)
Comment, the wolverine is a snow-adapted species that utilizes cold and
snowy habitats for multiple aspects of its life history. To inform our
assessment of the wolverine's status in the contiguous United States,
we updated our previous climate change analysis, the details of which
are summarized in the wolverine SSA report addendum (Service 2023, pp.
47-60). Our analysis focuses on the expected loss of snowpack out to
2100 in five modeling domains that overlap with occupied and potential
wolverine habitat in the contiguous United States across latitudinal,
longitudinal, and elevation gradients. The Service chose a snow depth
threshold of greater than or equal to 1 m (3.3 ft) to represent
significant snow cover on May 1, which provides a more conservative
estimate than was used in the 2018 SSA (i.e., greater than or equal to
0.5 m (20 in.) on May 1). This updated analysis shows that cold and
snowy conditions at high elevations are expected to decrease, with
spring snowpack at denning elevations decreasing as much as 50 percent
in some areas. As a result, we expect wolverine population resiliency
in the contiguous United States to decrease in the future. For more
information see Climate Change, below.
(8) Comment: We also received public comments recommending that the
North American wolverine not be listed as threatened or endangered
under the Act. One commenter stated that State wildlife agencies are
capable of managing the species and are able to provide protections
that ensure continued population growth towards population objectives
established by these agencies and that mandates of various Federal
resource management agencies provide a commitment to managing wildlife
habitat in a way that benefits all wildlife species, including
wolverines and other forest carnivores.
Our 2020 Response Summarized: We acknowledged that some members of
the public supported our decision to withdraw our proposed rule to list
the North American wolverine occurring in the contiguous United States
as a threatened species under the Act. In the wolverine SSA report
(Service 2018, appendix G), we provided a summary of the regulatory
protections provided by western States and Federal agencies, as well as
management measures being implemented, to conserve the wolverine and
its habitat. Trapping or hunting of wolverines was prohibited in the
contiguous United States when our October 13, 2020, withdrawal document
(85 FR 64618) published.
Our 2023 Response: We appreciate the regulatory protections and
management measures our State wildlife agency partners and Federal
resource management agencies have enacted to conserve the North
American wolverine and its habitat (Service 2018, appendix G). However,
we have determined that the contiguous U.S. DPS of North American
wolverine meets the Act's definition of a threatened species as
described in this rule due to future threats, including the reduction
in spring snowpack from climate change. This determination is not a
reflection on the adequacy of State management or the capability of
States to manage the species but rather an acknowledgement of the
serious threat posed to the species
[[Page 83733]]
by climate change. Along with the listing, we are finalizing an interim
4(d) rule that will promote conservation of the contiguous U.S. DPS of
North American wolverine by encouraging management of the landscape by
our partners in ways that meet the conservation needs of the wolverine.
The provisions of this 4(d) rule provide one of many tools we will use
to promote the conservation of the contiguous U.S. DPS of North
American wolverine.
(10) Comment: We received comments from several organizations that
support the listing of the North American wolverine and designation of
critical habitat. Threats cited include restricted migration, habitat
loss and connectivity related to threats from effects of climate
change, nontarget trapping pressures, road mortality and other effects
of roads (e.g., noise, pollution, fragmentation of habitat), motorized
recreation and traffic in wildlife corridors, timber sales and
associated roads, and effects of snowmobile traffic (habitat
fragmentation and pollution, and change in behavior).
Our 2020 Response Summarized: We found that demographic risks to
the species from either known or most likely potential stressors (i.e.,
disturbance due to winter recreational activities, other human
disturbances, effects of wildland fire, disease, predation,
overutilization, genetic diversity, small population effects, climate
change, and cumulative effects) were low based on our evaluation of the
best available information at the time in relation to current and
potential future conditions for the North American wolverine occurring
in the contiguous United States and in the context of the attributes
that affect the needs of the DPS (Service 2018, p. 103). Thus, we
determined that the North American wolverine in the contiguous United
States did not meet the definition of an endangered species or a
threatened species under the Act.
Our 2023 Response: Our 2018 wolverine SSA report and 2023 SSA
report addendum provide a thorough assessment of the threats affecting
the North American wolverine in the contiguous United States. New
information related to the threats affecting the contiguous U.S. DPS of
the North American wolverine have led us to a different conclusion than
the one we presented in our October 13, 2020, withdrawal document (85
FR 64618). In this final rule, we examine the best available
information about threats to the wolverine, including effects from
roads, disturbance due to winter recreational activity, other human
disturbance, effects from wildland fire, disease, predation,
overutilization (trapping), genetic diversity, small population
effects, and climate change, including the cumulative effects of these
threats. See Summary of Biological Status and Threats, below, for a
complete discussion of threats affecting the DPS. After assessing the
best available information, we conclude that the contiguous U.S. DPS of
the North American wolverine is not currently in danger of extinction
but is likely to become in danger of extinction within the foreseeable
future throughout all of its range.
(12) Comment: We received comments from several industry groups
supporting our August 13, 2014, withdrawal (79 FR 47522) of our
February 4, 2013, proposed rule (78 FR 7864) to list the North American
wolverine as threatened. In general, their support rests on the
following: (1) The DPS determination presented in our previous proposed
rules (both 2010 and 2013) was flawed; (2) the North American wolverine
does not meet the definition of a threatened species; (3) the obligate
relationship with denning and need for snow has not been adequately
addressed (and may be a habitat preference); and (4) climate model
projections do not support complete loss of snow. They also urged us to
reaffirm prior findings that winter recreation (motorized and
nonmotorized) is not a threat to wolverines.
Our 2020 Response Summarized: We reevaluated wolverines occurring
in the contiguous United States under our Policy Regarding the
Recognition of Distinct Vertebrate Population Segments Under the
Endangered Species Act (DPS policy; 61 FR 4722, February 7, 1996). See
Distinct Population Segment in the October 13, 2020, withdrawal
document (85 FR 64618 at 64628-64631) for more information. We provided
our analysis of the status of wolverines in the contiguous United
States under Determination of Species Status in the October 13, 2020,
withdrawal document (85 FR 64618 at 64645-64647). The topic of denning
behavior is discussed in the wolverine SSA report (see ``Use of Dens
and Denning Behavior'' under Reproduction and Growth in the wolverine
SSA report (Service 2018, pp. 23-28)). For our analysis of the effects
of climate change to North American wolverines and denning habitat, see
``Climate Change and Potential for Cumulative Effects'' in the October
13, 2020, withdrawal document (85 FR 64618 at 64642-64644).
Our 2023 Response: In this final rule, we provide our revised
evaluation of discreteness and significance under our DPS policy of the
segment of the North American wolverine occurring in the contiguous
United States considering new information available since the
publication of our October 13, 2020, withdrawal document (85 FR 64618).
We also explain how new information has led us to a different
determination from previous DPS analyses. The analysis contained in
this rulemaking supersedes and replaces any previous DPS analysis for
the segment of the North American wolverine occurring in the contiguous
United States. We conclude that the population of wolverines in the
contiguous United States is discrete and significant in relation to the
remainder of the species in North America. For more information, see
Distinct Population Segment Analysis for Wolverine in the Contiguous
United States, below.
The wolverine population in the contiguous United States is
expected to decrease in resiliency, redundancy, and representation in
the foreseeable future. The best available information suggests that
habitat loss as a result of climate change, and the resulting
exacerbating effect on other stressors, are likely to decrease the
viability of wolverines in the contiguous United States within this
century (see ``Summary of Future Condition'' and Determination of North
American Wolverine's Status, below). Our review of the best scientific
and commercial data available indicates that the contiguous U.S. DPS of
the North American wolverine meets the Act's definition of a threatened
species.
We acknowledge the precise causal mechanism(s) for the apparent
association of wolverine distribution with persistent spring snow are
not yet clear. The association could involve the importance of snow for
denning or other aspects of the species' biology and ecology. We
address uncertainties under Areas of Uncertainty for Wolverine Habitat
Needs, below. That said, we know that wolverines are a species that is
adapted to, and has a strong preference for, cold and snowy conditions
and that these conditions will be reduced in the future. The commenter
is accurate in that climate models do not predict a complete loss of
snow within the North American wolverine's range in the contiguous
United States. However, we expect climate change to reduce snowpack in
areas used by wolverines by as much as 50 percent in some places (see
our analysis under Climate Change, below). We conclude increasing
temperatures and decreasing snowpack have the
[[Page 83734]]
largest potential to influence the population viability of the
contiguous U.S. DPS of the North American wolverine in the future.
Regarding winter recreation, new information supports our
understanding that some forms of winter recreation, backcountry
motorized recreation especially, have the potential to negatively
impact wolverines. See our response to (4) Comment, above, and
Disturbance Due to Winter Recreational Activity, below, for further
details.
Comments From Tribes
(14) Comment: We received comments from one consortium of Tribal
nations stating that, based on the weight of evidence provided in our
previous rules, the North American wolverine meets the Act's definition
of endangered or threatened and is therefore warranted for listing.
Specific threats mentioned in the comment letter included current
population status, winter recreation activities, and effects of climate
change. The Tribes also included comments documenting the cultural
value of the wolverine and connection to cultural practices and concern
for the loss of wolverine populations in the contiguous United States.
The Tribes encouraged the Service to use sound and solid science in the
listing determination and noted that additional population monitoring
and Tribal climate change modeling efforts are under way to evaluate
the status of the wolverine.
Our 2020 Response Summarized: We appreciate the unique perspective
provided by the Tribal nations regarding the contribution of the North
American wolverine to the Tribes' culture and spirituality. We also
appreciate the commitment of the Tribal nations to continue studies of
wolverines.
We used the best available scientific information to provide a
detailed description of the North American wolverine's life history and
ecology, including a detailed discussion of wolverine denning habitat
and behavior. We conducted an analysis to assess the current population
status. Conservation measures and regulatory mechanisms relative to the
North American wolverine were also provided in the wolverine SSA
report. This information was used to evaluate the current and future
conditions of the DPS. We evaluated results from a fine-scale analysis
of the potential effects of climate change to future snowpack
conditions and found significant areas of snow (several hundred km\2\/
mi\2\) will persist on May 1 at elevations used by wolverines for
denning. We determined that, based on the best available information,
the North American wolverine in the contiguous United States did not
warrant listing as threatened or endangered under the Act in 2020.
Our 2023 Response: We appreciate the commitment of the Tribal
nations to further our knowledge of this unique species. We have
gathered the best available information on North American wolverines
and used this information to assess the current and future population
status of wolverines in the contiguous United States.
Regarding winter recreation, see our response to (4) Comment,
above, and Disturbance Due to Winter Recreational Activity, below, for
further details.
Regarding the effects of climate change to North American
wolverines, see our response to (1) Comment, above, and Climate Change,
below. We conclude that the contiguous U.S. DPS of the North American
wolverine is not currently in danger of extinction but is likely to
become in danger of extinction within the foreseeable future throughout
all of its range.
(15) Comment: We received comments from one Tribe whose territory
is occupied by the North American wolverine. The Tribe submitted a
comment letter in 2013 supporting our proposed listing. The Tribe
stated that the conservation and restoration of the wolverine and other
species within this homeland is of great importance to the Tribe's
subsistence, culture, religion, and economy. The letter also identified
conservation and management plans currently under development and
highlighted that the wolverine is designated as a species of concern in
these current draft plans. Specific comments were provided relative to
threats from climate change (including relative to demographic
stochasticity), recreation and urban development, and incidental take.
Included in those comments were references to other studies under way
(e.g., Adaptation Partners and climate change vulnerability
assessments; winter recreation study) to evaluate these potential
stressors.
Our 2020 Response Summarized: We appreciate the perspective
provided regarding the importance of the North American wolverine and
other species to the Tribe and its commitment to current and future
conservation and management actions. We also appreciate and evaluated
the information presented in the citations that were provided in the
comment letter. The best available scientific information was used to
evaluate the current conditions (i.e., potential stressors, including
winter recreation) and future conditions (e.g., effects of climate
change) of the DPS. Based on the best available information, we
determined that the North American wolverine in the contiguous United
States did not warrant listing as endangered or threatened under the
Act in 2020.
Our 2023 Response: Information previously provided by the Tribe was
considered in the 2018 SSA report. We include new and updated
scientific information in the 2023 wolverine SSA report addendum,
including information on the current conditions (i.e., potential
stressors, including winter recreation) and future conditions (e.g.,
effects of climate change) of the DPS. Based on the best available
information, we now determine that the contiguous U.S. DPS of the North
American wolverine meets the Act's definition of a threatened species.
State Agency Comments
In our October 13, 2020, withdrawal document (85 FR 64618), we also
addressed the extensive comments from several western States, including
previously submitted comments in response to the February 4, 2013,
proposed listing rule (78 FR 7864) as well as additional comments
submitted in response to our October 18, 2016, document that reopened
the public comment period on the 2013 proposed listing rule (81 FR
71670). These comments were grouped together and summarized as
described below.
(16) Comment: We received detailed comments critical of our
reliance on ``unverified'' climate model projections in our February 4,
2013, proposed listing rule, the lack of discussion of assumptions in
adopting the model findings, the lack of evaluating alternative
hypotheses, and the need to evaluate these effects at the den-site
scale. One State agency recommended that, given the disagreements in
the scientific community on the interpretation of these results, the
Service solicit an independent, scientific review of the February 4,
2013, proposed listing rule.
Our 2020 Response Summarized: In preparing the 2018 SSA report for
the North American wolverine, our foundational science document for
informing the October 13, 2020, withdrawal (85 FR 64618), we reviewed
available reports and peer-reviewed literature, incorporated survey
information for the purpose of preparing updated maps of the known
current and historical occurrences of the North American wolverine, and
contacted species experts to collect additional unpublished
information. We evaluated the appropriate analytical tools to
[[Page 83735]]
address data gaps and uncertainties. In some instances, we used
publications and other reports of the Eurasian subspecies (Gulo gulo
gulo) to fully inform our knowledge of the North American wolverine
(Gulo gulo luscus).
Before finalizing the 2018 SSA report, the draft wolverine SSA
report was submitted for peer review to four independent peer reviewers
and submitted to our Federal, State, and Tribal partners for scientific
review. We incorporated the results of these reviews in the 2018
wolverine SSA report, as appropriate.
We recognized that climate trends and future (2055 and later)
climate model projections indicated warming temperatures for much of
western North America, and changes to snowpack conditions. Our
assessment of climate change impacts indicated that large areas
(several hundred km\2\/mi\2\ for each study area) of future snow
(greater than 0.5 m (20 in) in depth) would persist on May 1 at
elevations currently used by wolverines for denning. This was true, on
average, across the range of climate models used out to approximately
year 2055.
Our 2023 Response: In the 2023 wolverine SSA report addendum, we
expanded upon our climate analysis from the 2018 SSA report. Both SSA
documents went through an independent, scientific peer review process.
The assessment of the climate modeling results, presented below under
Climate Change, and applied in the ``Summary of Future Condition''
discussion, replaces and supersedes the analysis of modeling results
presented in the February 4, 2013, proposed listing rule (78 FR 7864)
and the October 13, 2020, withdrawal document (85 FR 64618). We
acknowledge there are uncertainties around the nature of the
wolverine's relationship with cold and snowy conditions (see Areas of
Uncertainty for Wolverine Habitat Needs, below). Cold and snowy
conditions at high elevations favored by wolverines in the contiguous
United States are expected to decrease, with spring snowpack at denning
elevations decreasing as much as 50 percent in some areas.
(17) Comment: We received comments critical of our previous support
for findings by Schwartz et al. (2009) regarding effective population
size. Relatedly, several States commented on recent dispersal/movements
of wolverines into California, Colorado, and Utah as evidence of
population expansion.
Our 2020 Response Summarized: In the October 13, 2020, withdrawal
document (85 FR 64618), we referred to our response to (2) Comment for
a discussion of effective population size (85 FR 64618 at 64620).
Regarding recent occurrences of wolverines in the contiguous United
States, we noted that wolverines had recently been found in areas where
they were once extirpated in the contiguous United States. See
``Population Abundance and Density'' in the October 13, 2020,
withdrawal document (85 FR 64618 at 64634-64636) for more information.
Our 2023 Response: The best available estimate of effective
population size for the Northern Rocky Mountains continues to be that
provided by Schwartz et al. 2009 (p. 3226): 35 (credible interval = 28-
52). We estimated the effective population size of wolverines in the
North Cascades to be four (Service 2023, p. 27). We are not aware of
any other estimates of the effective population size of North American
wolverines in the contiguous United States. See also our response to
(2) Comment, above, and Effective Population Size in the Contiguous
United States, below, for more information.
We have gathered updated occurrence information in our 2023
wolverine SSA report addendum (Service 2023, figure 2). We acknowledge
that there are recent occurrences of wolverines in the western United
States in areas where they have not been reported for years or very
rarely (California, Colorado, Oregon, and Utah). These occurrences
outside of the known breeding distribution are encouraging, but there
is no evidence of breeding population expansion into California,
Colorado, Oregon, and Utah.
(18) Comment: We received comments from several western States
presenting clarifications or updates to incidental trapping events and
trapping regulations.
Our 2020 Response Summarized: We noted that trapping or hunting of
wolverines was not allowed in any western State (with the exception of
Alaska, which was not included in the DPS in our February 4, 2013,
proposed listing rule (78 FR 7864)). Legal protections for wolverines
are codified in western State laws and regulations concerning hunting
and trapping. Since 2013, there has been a zero quota for trapping or
harvest of wolverines in Montana. We described the documentation of
incidental trapping of wolverines in the contiguous United States (as
recently as December 2017) and noted that not all events resulted in
mortality. We acknowledged that both Idaho and Montana are implementing
trapper education programs to minimize nontarget wolverine captures.
Our 2023 Response: We gathered updated information from States
within the North American wolverine's range about incidental trapping,
trapping regulations, and measures taken by States to prevent
incidental trapping of wolverines. Lethal incidental trapping of
wolverines has been minimal (1 to 2 animals per year), primarily
occurring in Idaho and Montana. In the Overutilization for Commercial,
Recreational, Scientific, or Educational Purposes discussion, below, we
provide an assessment of incidental trapping and the measures States
are taking to reduce incidental trapping of wolverines.
(19) Comment: Several States provided comments in response to our
February 4, 2013, proposed listing rule (78 FR 7864) and our October
18, 2016, reopening of the public comment period (81 FR 71670)
indicating their disagreement with our determination of a wolverine DPS
for the contiguous United States. Specifically, some commenters stated
that the criteria of significance should be reevaluated, noting that
the February 4, 2013, proposed listing rule did not provide any
substantive information to support our conclusion that the loss of the
wolverine in the contiguous United States would result in a significant
gap in the range of the species; that is, our previous use of the loss
of latitudinal range does not provide a rational basis for concluding
that the loss of the wolverine in the contiguous United States would be
significant in relation to the taxon. Another commenter stated that the
wolverine population in the contiguous United States is connected
geographically and genetically to the Canada/Alaska populations and
these northern populations were likely the source of recolonization
during the 20th century. Further, this commenter stated there is not a
difference in control of exploitation and conservation status between
the United States and Canada.
Another commenter noted that, throughout the February 4, 2013,
proposed listing rule, the Service acknowledged that, historically, the
wolverine population in the contiguous United States was markedly
reduced by systematic predator control programs and unregulated
trapping. The commenter pointed out that areas of suitable habitat in
the North Cascades, where trapping has been minimal or nonexistent for
decades, and northern Rockies were recolonized by animals from Canada,
where relatively liberal trapping is still allowed. The commenter
asserted that our characterization in the February 4, 2013, proposed
listing rule of ``liberal''
[[Page 83736]]
Canadian regulations as sufficient to ``maintain the robust
conservation status of the Canadian population,'' does not comport with
our characterization that the very limited trapping in the contiguous
United States (Montana only) is insufficient to maintain the rebounding
population designated as a DPS.
Our 2020 Response Summarized: In light of the updated analysis and
new information included in the 2018 wolverine SSA report, we
reevaluated wolverines in the contiguous United States under our DPS
policy. We concluded that the population of wolverines in the
contiguous United States was not discrete in relation to the remainder
of the species in North America. As a result, in 2020, the population
of wolverines in the contiguous United States was not a listable entity
under section 3(16) of the Act. See Distinct Population Segment in the
October 13, 2020, withdrawal document (85 FR 64618 at 64627-64631) for
more information.
Our 2023 Response: As stated above, in this final rule we provide
our revised evaluation of discreteness and significance under the DPS
policy of the segment of the North American wolverine occurring in the
contiguous United States considering new information. We also explain
how new information has led us to different conclusions from previous
DPS analyses. The analysis contained in this rulemaking supersedes and
replaces any previous DPS analysis for the segment of the North
American wolverine occurring in the contiguous United States.
Regarding the commenter's concern with the significance analysis,
we have determined, as we did in the February 4, 2013, proposed listing
rule, that there is evidence that the loss of the wolverine in the
contiguous United States would result in a significant gap in the range
of the taxon. Based upon the loss of approximately 58,998,140 acres
(238,757 km\2\) of high-quality wolverine habitat from the southern
extent of the range and the adaptive potential that part of the range
provides against oncoming climate change impacts, and the 12-degree
latitudinal gap in the wolverine's range that would result if the U.S.
population was lost, we determine that the loss of the contiguous U.S.
wolverine population would result in a significant gap in the range of
the taxon. Thus, the DPS meets the definition of significant in our DPS
policy. For more information see Analysis of Significance, below.
Regarding the commenter's assertion that wolverines in the
contiguous United States are connected to Canada, which relates to the
discreteness analysis of our DPS policy, we do not consider wolverines
in the contiguous United States to be genetically or morphologically
discontinuous from wolverines in Canada (McKelvey et al. 2014, entire;
Pilgrim and Schwartz 2018, entire; Sawaya et al. 2023, entire).
Therefore, wolverines in the contiguous United States are not discrete
based on marked separation from other populations of the same taxon.
However, we determined that the wolverine meets the discreteness
criterion in our DPS policy (61 FR 4722; February 7, 1996), as
delimited by the international boundary with Canada and given
differences in control of exploitation, conservation status, and
regulatory mechanisms that are significant in light of section
4(a)(1)(D) of the Act. See Analysis of Discreteness, below, for more
information.
Finally, regarding the commenter's point about our characterization
in the February 4, 2013, proposed listing rule of trapping in Canada
versus the contiguous United States, we have considered updated
trapping information in our DPS analysis. New information available
since the publication of our October 13, 2020, withdrawal document (85
FR 64618) indicates that overharvest from trapping in Canada was likely
causing more of an impact than previously thought. Recent studies show
that harvest levels in portions of southeastern British Columbia and
southwestern Alberta were unsustainable and causing population declines
(Mowat et al. 2020, entire; Barrueto et al. 2022, entire) and could
negatively impact movement of individuals from Canada to the contiguous
United States (Sawaya 2023, pers. comm.). We now conclude that the
differences between Canada and the United States in control of
exploitation are significant in light of section 4(a)(1)(D) of the Act
and the wolverine population in the contiguous United States meets the
DPS policy's standard for ``discreteness.'' See Analysis of
Discreteness, below, for more information.
We conclude that the population of wolverines in the contiguous
United States is discrete and significant in relation to the remainder
of the species in North America. For our complete DPS analysis, see
Distinct Population Segment Analysis for Wolverine in the Contiguous
United States, below.
Comments Received in Response to Our November 23, 2022, Publication
As stated above, on November 23, 2022, we published a document in
the Federal Register (87 FR 71557) soliciting new information to update
the wolverine SSA so that we could reevaluate whether the North
American wolverine occurring in the contiguous United States is a
distinct population segment and, if so, whether the distinct population
segment meets the definition of an endangered or threatened species
under the Act. This document also notified the public that the February
4, 2013, proposed listing rule (78 FR 7864) had been reinstated as a
result of court action. In response to the November 23, 2022,
publication, we received additional information including survey
results, reports, documented mortalities, management efforts, and
recent wolverine literature that we evaluated and incorporated as
appropriate into our wolverine SSA report addendum. Although not
requested, we also received comments from submitters on topics related
to determinations regarding wolverine, including whether the wolverine
should or should not be listed as an endangered or threatened species
under the Act. The comments we received are similar to those we present
and respond to above.
Peer Reviewer Comments on the 2023 Wolverine SSA Report Addendum
We received comments from three peer reviewers on the draft
wolverine SSA report addendum. We reviewed all comments we received
from the peer reviewers for substantive issues regarding the
information contained in the wolverine SSA report addendum, as well as
any new information. The peer reviewers generally provided additional
references, clarifications, and suggestions, including further
definitions of some of the terms used in the wolverine SSA report
addendum. We updated the wolverine SSA report addendum based on the
peer reviewers' comments, including revising some of our adaptive
capacity scores, clarifying specific points where appropriate, and
adding additional details and suggested references where needed. Peer
reviewer comments are addressed in the following summary.
(PR1) Comment: Regarding our climate change analysis, one peer
reviewer did not agree with our initial characterization of the shared
socioeconomic pathway (SSP) 5-8.5 emissions scenario as worst case, and
stated there are possible scenarios that could be more extreme. They
also recommended the wolverine SSA report addendum more clearly point
out the uncertainty around the climate models and emissions scenarios
by stating the scenarios are representative of a large
[[Page 83737]]
portion of plausible outcomes, but not all.
Our Response: We addressed the peer reviewer's concern by removing
mention of likelihood when discussing specific emissions scenarios. We
also modified the text to include the latest guidance from the White
House Office of Science and Technology Policy on Selecting Climate
Information to Use in Climate Risk and Impact Assessments (OSTP 2023,
entire), which recommends using SSP5-8.5 as an upper bounding scenario.
We applied SSP5-8.5 as the upper bound to estimate future snow cover
available for wolverines within the selected domains.
(PR2) Comment: A peer reviewer questioned why we used the SSP2-4.5
and SSP5-8.5 emissions scenarios for our future condition analysis.
They suggested we use SSP1-1.9 instead of SSP2-4.5 since it is the
opposite extreme of SSP5-8.5.
Our Response: For our future analysis, we used SSP2-4.5 because
that emissions scenario is closest to the current emissions trajectory
we are on now, which provides a plausible lower boundary estimate of
future snow cover available for North American wolverines. The
Intergovernmental Panel on Climate Change (IPCC) has recently deemed
our ability to limit warming to 1.5 [deg]C (2.7 [deg]F) (SSP1-1.9) as
``impossible'' with no or limited overshoot in its 2022 gap analysis
(Riahi et al. 2022, p. 298). Scenario SSP5-8.5 reflects a no-emissions
mitigation policy, which provides a plausible upper boundary estimate
of available future snow cover.
(PR3) Comment: A peer reviewer was concerned that the wolverine SSA
report addendum did not list snow as an important attribute when
studies have shown dens are concordant with spring snow coverage. The
peer reviewer disagreed with our reasoning for excluding snow, which
was because we do not know how it impacts survival and reproduction,
and stated we should also remove food habits, physical features, and
home range size since it is not clear how any of these impact survival
and reproduction. They believe the case for snow is much stronger than
any of these other factors.
Our Response: We considered the information provided and addressed
the peer reviewer's concern by updating the wolverine SSA report
addendum to include snow as an important attribute of wolverine
habitat.
(PR4) Comment: One peer reviewer was concerned about the use of
spring snow cover for distribution. They questioned our use of the term
``persistent spring snow'' and the May 15 end date that is often
associated with the term. The peer reviewer recommended analyzing snow
cover between February and March, when young are newborn and most in
need of thermal cover in natal dens. The reviewer believed that any
analysis of climate change effects at those more critical times for
denning would not likely show impacts.
Our Response: We used the term ``persistent spring snow'' in the
wolverine SSA report addendum because it is a term frequently used in
the scientific literature for wolverines and appears to be correlated
to the wolverine's circumpolar distribution. Snow model outputs for May
1 are presented in the 2023 wolverine SSA report addendum. May 1 was
used based on previous studies documented in the 2018 SSA (Service
2018, p. 26), indicating wolverine den site abandonment generally
occurs before May 1. We acknowledge that young kits are in natal dens
usually from mid-February to mid-March, so the use of May 1 snow
projections is a conservative approach, but one which is consistent
with the literature.
As described in the wolverine SSA report addendum, there are a
number of hypotheses for why wolverines prefer cold and snowy habitats,
and not all of them are limited to denning (i.e., easier to get food,
more food caching sites, etc.). These things could be important for
adults throughout the breeding cycle or for juveniles as they become
more independent from their mothers. We also discuss the possibility of
other factors that are correlated to persistent spring snow, such as
low temperatures (also analyzed in Copeland et al. 2010, entire), being
the causal mechanisms for the observed relationship. In the wolverine
SSA report addendum, we acknowledge wolverines have been documented
denning in areas without persistent spring snow (Aronsson and Persson
2017, p. 266; Copeland et al. 2010, pp. 240-242; Fisher et al. 2022, p.
8; Jokinen et al. 2019, pp. 6-8; Persson et al. 2023, entire; Webb et
al. 2016, pp. 1466-1467); however, this phenomenon appears to be
associated with cold, high-latitude boreal or arctic forests rather
than the alpine habitats used by wolverines in the contiguous United
States. In the contiguous United States, there is no evidence that
wolverines have denned in areas without persistent spring snow.
(PR5) Comment: One peer reviewer recommended including potential
ways wolverines could adapt their denning behavior or use smaller or
shallower patches of snow for denning in response to effects from
climate change.
Our Response: We added language to the wolverine SSA report
addendum to address this comment and we also included additional text
that snow may be important for more than just denning. As stated above,
there is no evidence that wolverines have denned in areas without
persistent spring snow in the contiguous United States.
(PR6) Comment: A peer reviewer pointed out that future recreation
will not just increase due to an increase in the human population, but
also because snow-dependent recreational activities will be constrained
to a smaller area that still contains quality snow in the future.
Our Response: We included text in the wolverine SSA report addendum
reflecting the reviewer's comment.
(PR7) Comment: One peer reviewer suggested adding Colorado's
wolverine reintroduction plan to the wolverine SSA report addendum as a
voluntary conservation measure.
Our Response: We updated the wolverine SSA report addendum to
include a description of Colorado Parks and Wildlife's previous
consideration of reintroducing wolverines to Colorado as a nonessential
experimental population (see 78 FR 7890, February 4, 2013). We also
describe how this proposal was subsequently withdrawn in 2014 (see 79
FR 47522, August 13, 2014), when we withdrew the February 4, 2013,
proposed listing rule (78 FR 7864), and that there is currently no
formal proposal to reintroduce wolverines to Colorado.
(PR8) Comment: Two peer reviewers provided additional documentation
regarding roads acting as a barrier to wolverine dispersal. Both
provided different situations where at least one wolverine was seen
crossing roadways, including a multiple-lane highway. One peer reviewer
also mentioned regularly seeing wolverine tracks crossing roadways.
Our Response: We updated the wolverine SSA report addendum to
reflect these observations and modified the text to clarify that
highways can limit female gene flow in some situations, but they are
not complete barriers to wolverine movements.
(PR9) Comment: One peer reviewer questioned how the artificial
cutoff of the U.S.-Canada international border influenced the results
of the 2009 effective population size analysis (Schwartz et al. 2009,
entire).
Our Response: The effective population size estimate was only for
the U.S. portion of the Northern Rockies, and there were no samples
taken from Canada. As we stated in the wolverine SSA report addendum,
connectivity to larger source
[[Page 83738]]
populations can alleviate the adverse effects of small effective
population sizes (Frankham et al. 2014, entire). We also added a
paragraph to the wolverine SSA report addendum to explain that because
effective population size estimates for wolverine are small,
connectivity with populations in Canada to allow for migration and gene
flow is crucial to maintaining genetic diversity.
(PR10) Comment: One peer reviewer was concerned that current data
for the wolverine are not being compared to what is known historically.
They specifically called out the comparison of population sizes, the
distribution and abundance of wolverines in the contiguous United
States, and the results of genetic studies.
Our Response: As the peer reviewer mentioned, there is a lack of
historical data to compare to current conditions. However, our
assessment is a forward-looking one, based on current and future
conditions, and not the change from historical conditions to current
conditions.
(PR11) Comment: One peer reviewer questioned the 40 percent decline
in wolverine abundance within a national park complex in southwestern
Canada (Mowat et al. 2020, entire; Barrueto et al. 2022, entire).
Our Response: The Barrueto et al. (2022) effort is a decade-long
research project that was peer reviewed and published in a scientific
journal. We note that the initial population estimate was approximately
50 wolverines at the start of the study, so a 40 percent decline over
10 years results in the loss of approximately 15-20 wolverines. The
wolverine SSA report addendum has been updated to provide this
additional detail.
(PR12) Comment: A peer reviewer suggested including additional
detail on how species-specific trapping and snaring reduce the
likelihood of incidentally capturing a wolverine.
Our Response: We updated the wolverine SSA report addendum to
include how trappers use pan tension, site selection, and snare height
to reduce the likelihood of incidental capture. We also included
additional information we received from the States on their efforts to
reduce incidental trapping of wolverines.
(PR13) Comment: One peer reviewer suggested that the median and
quartiles presented in our modeling may not accurately capture the
variability in environmental conditions. The reviewer suggested that in
addition to calculating the lower-quartile, median, and upper-quartile
at each individual grid cell and timestep, we should also calculate the
maximum and minimum bracketing response.
Our Response: We did not conduct the additional suggested analysis.
The additional analysis would require significant work and time, and we
conclude our approach includes the majority of plausible future
outcomes and incorporates the best available information to inform our
listing determination.
I. Final Listing Determination
Background
A comprehensive review of the life history, population trends, and
ecology of the North American wolverine is presented in the wolverine
SSA report (Service 2018, pp. 3-44) and wolverine SSA report addendum
(Service 2023, entire). The Service recognizes the North American
wolverine as the subspecies Gulo gulo luscus (Service 2018, p. 8).
Wolverines are a medium-sized (about 1 m (3.3 feet (ft)) in length)
carnivore, with a large head, broad forehead, and short neck (Service
2018, p. 4). Wolverines have heavy musculature and relatively short
legs, and large feet with strong, curved claws for digging and climbing
(Service 2018, p. 4). Their feet are adapted for travel through deep
snow and, during the winter, dense, stiff, bristle-type hairs are found
between the toes and around the foot pad. This characteristic becomes
diminished in the summer (Service 2018, p. 4). The wolverine is the
largest terrestrial member of the Mustelidae family, which includes
weasel, fisher, mink, marten, and others, and resembles a small bear
with a bushy tail (Service 2018, p. 1). Wolverines possess a number of
morphological and physiological adaptations that allow them to travel
long distances, and they maintain large territories in remote areas
(Service 2018, p. 1). They have been described as curious, intelligent,
and playful but cautious animals, though their social behavior and
social organization has not been well-studied (Service 2018, p. 1). In
North America, wolverines are found in Alaska, much of Canada, and the
western-northwestern United States.
During the late 1800s and early 1900s, the wolverine population
declined or was extirpated in much of the contiguous United States
(lower 48 States), which was most likely the result of unregulated
trapping and predator poisoning campaigns. Following regulation of
trapping and restrictions on the use of poison, the wolverine
population rebounded to some extent, and their distribution expanded to
refill a portion of their previously extirpated range. In the
contiguous United States, wolverines are known to reproduce in
Washington, Idaho, Montana, and Wyoming (Service 2023, figure 3).
Solitary individuals or lone dispersing individuals have been observed
in other western States (Oregon, Colorado, Utah, and California), but
there is no evidence of reproduction in the contiguous United States
outside of the Northern Rocky Mountains in Idaho, Montana, and Wyoming
and the Cascade Mountains of Washington.
Regulatory and Analytical Framework
Regulatory Framework
Section 4 of the Act (16 U.S.C. 1533) and the implementing
regulations in title 50 of the Code of Federal Regulations set forth
the procedures for determining whether a species is an endangered
species or a threatened species, issuing protective regulations for
threatened species, and designating critical habitat for endangered and
threatened species. In 2019, jointly with the National Marine Fisheries
Service, the Service issued a final rule that revised the regulations
in 50 CFR part 424 regarding how we add, remove, and reclassify
endangered and threatened species and the criteria for designating
listed species' critical habitat (84 FR 45020; August 27, 2019). On the
same day, the Service also issued final regulations that, for species
listed as threatened species after September 26, 2019, eliminated the
Service's general protective regulations automatically applying to
threatened species the prohibitions that section 9 of the Act applies
to endangered species (84 FR 44753; August 27, 2019).
The Act defines an ``endangered species'' as a species that is in
danger of extinction throughout all or a significant portion of its
range, and a ``threatened species'' as a species that is likely to
become an endangered species within the foreseeable future throughout
all or a significant portion of its range. The Act requires that we
determine whether any species is an endangered species or a threatened
species because of any of the following factors:
(A) The present or threatened destruction, modification, or
curtailment of its habitat or range;
(B) Overutilization for commercial, recreational, scientific, or
educational purposes;
(C) Disease or predation;
(D) The inadequacy of existing regulatory mechanisms; or
(E) Other natural or manmade factors affecting its continued
existence.
These factors represent broad categories of natural or human-caused
[[Page 83739]]
actions or conditions that could have an effect on a species' continued
existence. In evaluating these actions and conditions, we look for
those that may have a negative effect on individuals of the species, as
well as other actions or conditions that may ameliorate any negative
effects or may have positive effects.
We use the term ``threat'' to refer in general to actions or
conditions that are known to or are reasonably likely to negatively
affect individuals of a species. The term ``threat'' includes actions
or conditions that have a direct impact on individuals (direct
impacts), as well as those that affect individuals through alteration
of their habitat or required resources (stressors). The term ``threat''
may encompass--either together or separately--the source of the action
or condition or the action or condition itself.
However, the mere identification of any threat(s) does not
necessarily mean that the species meets the statutory definition of an
``endangered species'' or a ``threatened species.'' In determining
whether a species meets either definition, we must evaluate all
identified threats by considering the species' expected response and
the effects of the threats--in light of those actions and conditions
that will ameliorate the threats--on an individual, population, and
species level. We evaluate each threat and its expected effects on the
species, then analyze the cumulative effect of all of the threats on
the species as a whole. We also consider the cumulative effect of the
threats in light of those actions and conditions that will have
positive effects on the species, such as any existing regulatory
mechanisms or conservation efforts. The Secretary determines whether
the species meets the definition of an ``endangered species'' or a
``threatened species'' only after conducting this cumulative analysis
and describing the expected effect on the species now and in the
foreseeable future.
The Act does not define the term ``foreseeable future,'' which
appears in the statutory definition of ``threatened species.'' Our
implementing regulations at 50 CFR 424.11(d) set forth a framework for
evaluating the foreseeable future on a case-by-case basis. The term
``foreseeable future'' extends only so far into the future as we can
reasonably determine that both the future threats and the species'
responses to those threats are likely. In other words, the foreseeable
future is the period of time in which we can make reliable predictions.
``Reliable'' does not mean ``certain''; it means sufficient to provide
a reasonable degree of confidence in the prediction. Thus, a prediction
is reliable if it is reasonable to depend on it when making decisions.
It is not always possible or necessary to define the foreseeable
future as a particular number of years. Analysis of the foreseeable
future uses the best scientific and commercial data available and
should consider the timeframes applicable to the relevant threats and
to the species' likely responses to those threats in view of its life-
history characteristics. Data that are typically relevant to assessing
the species' biological response include species-specific factors such
as lifespan, reproductive rates or productivity, certain behaviors, and
other demographic factors.
Analytical Framework
The wolverine SSA report and SSA report addendum document the
results of our comprehensive biological review of the best scientific
and commercial data regarding the status of the North American
wolverine, including an assessment of the potential threats to the
subspecies occurring in the contiguous United States. The wolverine SSA
report and SSA report addendum do not represent our decision on whether
the North American wolverine should be listed as an endangered or
threatened species under the Act. However, they do provide the
scientific basis that informs our regulatory decisions, which involve
the further application of standards within the Act and its
implementing regulations and policies.
To assess viability of the North American wolverine occurring in
the contiguous United States, we used the three conservation biology
principles of resiliency, redundancy, and representation (Shaffer and
Stein 2000, pp. 306-310). Briefly, resiliency is the ability of the
species to withstand environmental and demographic stochasticity (for
example, wet or dry, warm or cold years); redundancy is the ability of
the species to withstand catastrophic events (for example, droughts,
large pollution events), and representation is the ability of the
species to adapt to both near-term and long-term changes in its
physical and biological environment (for example, climate conditions,
pathogen). In general, species viability will increase with increases
in resiliency, redundancy, and representation (Smith et al. 2018, p.
306). Using these principles, we identified the subspecies' ecological
requirements for survival and reproduction at the individual,
population, and species levels, and described the beneficial and risk
factors influencing the subspecies' viability.
The SSA process can be categorized into three sequential stages.
During the first stage, we evaluated the individual subspecies' life-
history needs. The next stage involved an assessment of the historical
and current condition of the subspecies' demographics and habitat
characteristics, including an explanation of how the species arrived at
its current condition. The final stage of the SSA involved making
predictions about the subspecies' responses to positive and negative
environmental and anthropogenic influences. Throughout all of these
stages, we used the best available information to characterize
viability as the ability of a species (which, under the Act, includes
any subspecies of fish or wildlife or plants, and any DPS of any
species of vertebrate fish or wildlife which interbreeds when mature)
to sustain populations in the wild over time. We use this information
to inform our regulatory decision.
Later in this document, we present a summary of the key results and
conclusions from the 2018 wolverine SSA report and 2023 wolverine SSA
report addendum; the full SSA report and SSA report addendum can be
found at Docket No. FWS-R6-ES-2023-0216 on <a href="https://www.regulations.gov">https://www.regulations.gov</a>
and at <a href="https://ecos.fws.gov/ecp/species/5123">https://ecos.fws.gov/ecp/species/5123</a>.
Distinct Population Segment
Pursuant to the Act, we must consider for listing any species,
subspecies, or, for vertebrates, any DPS of these taxa, if there is
sufficient information to indicate that such action may be warranted.
To interpret and implement the DPS provision of the Act and
Congressional guidance, the Service and the National Marine Fisheries
Service published, on February 7, 1996, an interagency Policy Regarding
the Recognition of Distinct Vertebrate Population Segments under the
Act (DPS policy; 61 FR 4722, February 7, 1996). The DPS policy
addresses the recognition of DPSs for potential listing actions. The
DPS policy allows for more refined application of the Act that better
reflects the biological needs of the taxon being considered, and avoids
the inclusion of entities that do not require its protective measures.
Under our DPS policy, three elements are considered in a decision
regarding the status of a possible DPS as endangered or threatened
under the Act. These are applied similarly for additions to the Lists
of Endangered and Threatened Wildlife and Plants (Lists),
reclassification, and removal from the Lists. They are: (1)
Discreteness of the
[[Page 83740]]
population segment in relation to the remainder of the taxon; (2) the
biological or ecological significance of the population segment to the
taxon to which it belongs; and (3) the population segment's
conservation status in relation to the Act's standards for listing
(i.e., whether the population segment is, when treated as if it were a
species or subspecies, an endangered or threatened species).
Discreteness refers to the degree of isolation of a population from
other members of the species, and we evaluate this factor based on
specific criteria. If a population segment is considered discrete, we
must consider whether the discrete segment is ``significant'' to the
taxon to which it belongs by using the best available scientific and
commercial information. When determining if a potential DPS is
significant, our policy directs us to sparingly list DPSs while
encouraging the conservation of genetic diversity. If we determine that
a population segment is both discrete and significant, we then evaluate
it for endangered or threatened species status based on the Act's
standards.
We have conducted several DPS analyses of wolverines in the
contiguous United States since 2010 in response to new information and
legal challenges. We first found that the population qualified as a DPS
in our 2010 12-month finding (75 FR 78030; December 14, 2010) on a
petition to list the population as a DPS. We reaffirmed and summarized
this finding in our February 4, 2013, proposed listing rule (78 FR
7864). In 2020, we reversed our previous finding, based on information
at the time which suggested the population was not discrete from
wolverine populations in Canada (85 FR 64618; October 13, 2020). Below,
we provide our revised evaluation of discreteness and significance
under the DPS policy of the segment of the North American wolverine
occurring in the contiguous United States. Where necessary and
appropriate below, we explain how new information has led us to
different conclusions from previous DPS analyses. The analysis
contained in this rulemaking supersedes and replaces any previous DPS
analysis for the segment of the North American wolverine occurring in
the contiguous United States. We determined that the contiguous U.S.
population of the North American wolverine meets the discreteness
criterion in our DPS policy; it is delimited by the international
boundary with Canada, and there are differences between the United
States and Canada regarding control of exploitation, conservation
status, and regulatory mechanisms that are significant in light of
section 4(a)(1)(D) of the Act. We then determined that the North
American wolverine population occurring in the contiguous United States
is significant because its loss would result in a significant gap in
the range of the taxon.
Distinct Population Segment Analysis for Wolverine in the Contiguous
United States
Analysis of Discreteness
Under our DPS policy, a population segment of a vertebrate species
may be considered discrete if it satisfies either one of the following
conditions: (1) It is markedly separated from other populations of the
same taxon as a consequence of physical, physiological, ecological, or
behavioral factors (quantitative measures of genetic or morphological
discontinuity may provide evidence of this separation); or (2) it is
delimited by international governmental boundaries within which
differences in control of exploitation, management of habitat,
conservation status, or regulatory mechanisms exist that are
significant in light of section 4(a)(1)(D) of the Act (inadequacy of
existing regulatory mechanisms).
Discreteness Based on Marked Separation
In our February 4, 2013, proposed listing rule (78 FR 7864), we did
not find marked separation from other populations to support
discreteness of the contiguous U.S. wolverine population. We also did
not find marked separation to support discreteness in our October 13,
2020, withdrawal (85 FR 64618). Our review of the new information
presented in the 2023 wolverine SSA report addendum has not altered
that conclusion; we continue to find that there are no physical,
physiological, ecological, or behavioral factors separating wolverines
in the contiguous United States from wolverines in Canada. We do not
consider wolverines in the contiguous United States to be genetically
or morphologically discontinuous from wolverines in Canada based on
genetic information that supports that Canadian wolverines repopulated
the contiguous United States over the past several decades and there
are no unique haplotypes in the contiguous U.S. population (McKelvey et
al. 2014, entire; Pilgrim and Schwartz 2018, entire; Sawaya et al.
2023, entire). Therefore, wolverines in the contiguous United States
are not discrete based on marked separation from other populations of
the same taxon.
We next evaluate whether the wolverine population in the contiguous
United States is discrete based on the international boundary with
Canada. We separately consider below whether there is discreteness
based on differences between the two countries in terms of control of
exploitation, management of habitat, conservation status, or regulatory
mechanisms that are significant in light of section 4(a)(1)(D) of the
Act (inadequacy of existing regulatory mechanisms).
Discreteness Based on the International Border--Differences in Control
of Exploitation
In our 2010 12-month finding (75 FR 78030; December 14, 2010) and
2013 proposed listing rule (78 FR 7864; February 4, 2013), we noted
that differences in control of exploitation exist between the United
States and Canada, but concluded those differences did not result in
discreteness because the differences favored the contiguous U.S.
population, the population that is at risk. In the wolverine 2018 SSA
report, we noted that trapping or hunting of wolverines is currently
prohibited in the contiguous United States and is allowed in Canada
(Service 2018, pp. 68-69). In that 2018 SSA report, we included an
analysis of trapping efforts in southern Canada and trapping effort
along the U.S.-Canada border, and based on that analysis, we found
trapping to be limited. We again concluded in our October 13, 2020,
withdrawal document (85 FR 64618) that the differences in exploitation
were not significant in light of section 4(a)(1)(D) of the Act
(inadequacy of existing regulatory mechanisms).
However, new information available since the publication of the
October 13, 2020, withdrawal document indicates that trapping in Canada
was likely causing more of an impact than previously thought. Recent
studies show that harvest levels in portions of southeastern British
Columbia and southwestern Alberta were unsustainable and causing
population declines (Mowat et al. 2020, entire; Barrueto et al. 2022,
entire). The areas evaluated are close enough to the international
border that dispersing individuals would be likely to provide important
genetic diversity and demographic rescue to the population in the
contiguous United States. Harvest levels in Canada could negatively
impact movement of individuals from Canada because, with reduced
populations in Canada, there is less pressure on individuals to move
south to areas in the United States to find suitable vacant home ranges
(Sawaya
[[Page 83741]]
2023, pers. comm.). Furthermore, female wolverines appear less likely
to disperse long distances or across major roadways compared to males
(Sawaya et al. 2019, pp. 621-23). According to the latest genetic
analyses, virtually all of the recent movement of wolverines from
Canada to the United States appears to be by males (Sawaya et al. 2023,
pp. 12-14, 17). Although there is now a trapping moratorium in
southeastern British Columbia (British Columbia 2022, p. 76), it is
unclear how long the moratorium will be in place or what the legacy
effects of recent overharvest in southern British Columbia will be. In
addition, trapping continues to be allowed in portions of southern
Alberta. We conclude that harvest in Canada will continue to be an
impediment to effective dispersal of wolverines into the United States.
This, in turn, is likely to impact future genetic integrity of the
population in the contiguous United States and limit the ability for
demographic rescue should wolverines decline in number within the
contiguous United States. Thus, we now conclude, based on new
information, that the differences between Canada and the United States
in control of exploitation are significant in light of section
4(a)(1)(D) of the Act. Existing regulations in Canada have been
inadequate to address this exploitation. Alberta continues to allow
trapping in areas important for potential dispersing wolverines, and
there is uncertainty on the length and effectiveness of the trapping
moratorium in British Columbia and the long-term population effects of
the recent overharvest there. As a result, we conclude the wolverine
population in the contiguous United States meets the standard of
``discreteness'' and we use the international border between the United
States and Canada to define the northern boundary of the contiguous
U.S. wolverine discrete population.
Discreteness Based on the International Border--Differences in
Management of Habitat
In the 2013 proposed listing rule (78 FR 7864; February 4, 2013)
and October 13, 2020, withdrawal document (85 FR 64618), we stated that
management activities (e.g., timber harvest, wildland firefighting,
prescribed fire, and silviculture) can modify wolverine habitat, but
this species appears to be little affected by changes to the vegetative
characteristics of its habitat. However, recent research in Canada
indicates that wolverines and other carnivores can be displaced from
habitat that is subject to human disturbance that includes harvest cut-
blocks in forested habitat (Frey et al. 2020, entire). That said, most
wolverine habitat in the contiguous United States occurs at high
elevations in rugged terrain that is not usually conducive to intensive
forms of silviculture and timber harvest. Although recent information
indicates wolverines may be affected by disturbance from some types of
habitat management, these disturbances occur in both the contiguous
United States and southern Canada, where forested alpine habitats are
managed in relatively similar ways and are relatively limited in scope
and scale in wolverine habitat. Therefore, there are no significant
differences in management of habitat between the United States and
Canada pursuant to 4(a)(1)(D) of the Act.
Discreteness Based on the International Border--Differences in
Conservation Status
In the December 14, 2010, 12-month finding (75 FR 78030), which is
summarized in the February 4, 2013, proposed listing rule (78 FR 7864),
we found that the wolverine population in the contiguous United States
met the second DPS discreteness condition because of differences in
conservation status as delimited by the U.S.-Canada international
governmental boundary. We found that those differences were substantial
and significant in light of section 4(a)(1)(D) of the Act. We stated
that in the remaining current range in Canada and Alaska, wolverines
exist in well-distributed, interconnected, large populations. We added
that, conversely, wolverine populations in the remaining contiguous
U.S. range appear to be at numbers so low that their continued
existence could be at risk, especially in light of the threats to the
subspecies. In the 2010 12-month finding, we stated that risks come
from three main factors: (1) Small total population size; (2) effective
population size below that needed to maintain genetic diversity and
demographic stability; and (3) the fragmented nature of wolverine
habitat in the contiguous United States that results in smaller,
isolated patches separated by unsuitable habitat. As a result, we
concluded that the contiguous U.S. population of the wolverine met the
discreteness criterion in our DPS policy. Consequently, we used the
international border between the United States and Canada to define the
northern boundary of the contiguous U.S. DPS of the North American
wolverine in our December 14, 2010, 12-month finding (75 FR 78030) and
our February 4, 2013, proposed listing rule (78 FR 7864).
In our October 13, 2020, withdrawal document (85 FR 64618), based
on new information at the time, we concluded there were not significant
differences in control of exploitation, conservation status, and
management of habitat, nor other threats to the wolverine requiring
regulatory mechanisms to address them, and we concluded that there are
no differences in regulatory mechanisms between the United States and
Canada that are significant in light of section 4(a)(1)(D) of the Act.
As a result, we concluded that the contiguous U.S. population of the
North American wolverine did not meet the discreteness criterion in our
DPS policy. Below, we revisit discreteness based on the international
border and differences in conservation status considering new
information presented in the wolverine SSA report addendum.
Small Total Population Size--Wolverine population densities vary
across North America and have been described as naturally low (van Zyll
de Jong 1975, p. 434) given the species' large home range, wide-ranging
movements, and solitary characteristics (Service 2018, p. 56). There
are far fewer wolverines in the contiguous United States (around 300)
than there are in Canada (more than 15,000) and Alaska (likely in the
thousands) (Committee on the Status of Endangered Wildlife in Canada
(COSEWIC) 2014, pp. 36, 47; Inman et al. 2013, p. 282; Service 2018, p.
71), but this is largely a reflection of the amount of suitable habitat
available within the contiguous United States (both currently and
historically) for a species that needs large, exclusive territories.
Even if wolverines occupied all available habitat in the contiguous
United States, their populations would still be relatively small
compared to Canada (i.e., the population capacity estimate was 644 (95%
confidence interval (CI) = 506-1881) (Inman et al. 2013, p. 282). A
small population in the contiguous United States would be less of a
conservation concern if there were greater connectivity with the larger
populations in Canada.
Recent genetic information indicates wolverines from Canada have
slowly repopulated the contiguous United States over the past century
since the era of unregulated predator removal (Service 2018, pp. 45-50;
Sawaya 2023, pers. comm.). We stated in the December 14, 2010, 12-month
finding (75 FR 78030) that differences in population sizes between the
contiguous United States and Canada were reflective of a difference in
conservation status. In our October 13, 2020, withdrawal document (85
FR 64618), based on new information, we concluded that the contiguous
U.S. wolverines represent a peripheral
[[Page 83742]]
population at the southern extent of the North American wolverine's
range. Thus, we considered the small population size of wolverines in
the United States to be a natural result of the limited habitat
available and not reflective of a difference in conservation status.
Our 2020 determination on this point was made with the understanding
that there was sufficient connectivity with Canada such that dispersing
wolverines could bolster the small population in the contiguous United
States. However, new information on wolverine dispersal and genetic
connectivity indicates that wolverines appear to be impacted by recent
overharvest in Canada, barriers to female wolverine dispersal, and
development in dispersal corridors between suitable habitat (Barrueto
et al. 2022, p. 4; Sawaya et al. 2023, pp. 12-14; Balkenhol et al.
2020, p. 799). Because of this, the small population in the contiguous
United States is more at risk from future threats impacting population
resiliency. We now conclude that the difference in population size on
the contiguous U.S. side of the international border is a significant
difference in conservation status in light of section 4(a)(1)(D) of the
Act as it applies to discreteness.
Effective Population Size--In our December 14, 2010, 12-month
finding (75 FR 78030) and February 4, 2013, proposed listing rule (78
FR 7864), in support of our conclusion that differences in conservation
status between the United States and Canada exist that are significant
in light of section 4(a)(1)(D) of the Act, we discussed the difference
in wolverine effective population size between the contiguous United
States and Canada. The 2013 proposed listing rule presented an
effective population size estimate for wolverines in the contiguous
United States from a publication by Schwartz et al. (2009), which
estimated a summed effective population size of 35, with credible
limits from 28 to 52 (Schwartz et al. 2009, p. 3,226). As provided in
our SSA report (Service 2018, pp. 46-47), effective population sizes
(N<INF>e</INF>) are typically smaller than census population sizes.
N<INF>e</INF> is the number of individuals in a population that would
result in the same loss of genetic diversity, inbreeding, and genetic
drift, if they behaved in the manner of an idealized population (equal
sex ratio, random mating, all adults producing offspring, equal numbers
of offspring per parent, and a constant number of breeding individuals
across generations) (Frankham 1995, p. 96). The concept of effective
population size relates to population viability because, as a general
rule, closed populations with random mating that have effective
population sizes (1) below 50 are at higher risk of inbreeding
depression, and (2) below 500 are more likely to lose genetic variation
important to maintaining long-term evolutionary potential. In addition,
small, isolated populations are more vulnerable to extinction through
interactions between environmental, genetic, and demographic factors
(Caughley 1994, pp. 221-227). Importantly, the concept and guidelines
for genetically effective population size were developed for a single,
isolated population (Laikre et al. 2016, p. 280). Fragmentation can
further exacerbate inbreeding depression and genetic loss, while
connectivity to larger source populations can alleviate the adverse
effects of small effective population sizes (Frankham et al. 2014, p.
60).
In our October 13, 2020, withdrawal document (85 FR 64618), we
acknowledged the low effective population size of wolverines in the
contiguous United States but found this was not a concern given the
evidence of genetic connectivity between the United States and Canada.
We stated the currently known spatial distribution of genetic
variability in wolverines in North America appeared to be a reflection
of a complex history where population abundance has fluctuated since
the time of the last glaciation and insufficient time has passed since
human persecution for a full recovery of wolverine densities (Cardinal
2004, pp. 23-24; Zigouris et al. 2012, p. 1,554). Zigouris et al.
(2012, p. 1,545) posit that the irregular distribution of wolverines in
the southwestern periphery and the genetic diversity observed in those
analyses is a result of population bottlenecks that were caused by
range contractions from a panmictic (random mating) northern core
population approximately 150 years ago coinciding with human
persecution. We stated that very few successful migrants are needed per
generation to maintain at least 95 percent of the genetic variation in
the next 100 generations (approximately 750 years) in the contiguous
United States (Cegelski et al. 2006, p. 209). We concluded that this
level of migration from the north had already been occurring following
the end of intense predator removal campaigns that affected this
subspecies. Given observations of wolverines moving vast distances over
varied terrain and across the U.S.-Canada border, our assessment of the
low levels of trapping mortality in Canada near the border, and further
confirmation of Canada as the source of wolverine genetics present in
contiguous U.S. wolverines, we believed that wolverines in the
contiguous United States were not separated genetically from the larger
population in Canada. In our October 13, 2020, withdrawal document (85
FR 64618), we concluded that wolverines in the contiguous United States
exhibit genetic and phenotypic similarities with wolverines in Canada
that implied connectivity with Canada. As such, we concluded in that
withdrawal document that it was not biologically appropriate to
consider the low effective population size of wolverines on the
contiguous U.S. side of the border as a difference in conservation
status that is significant in light of section 4(a)(1)(D) of the Act as
it applies to discreteness.
In our 2023 wolverine SSA report addendum, we summarized our
evaluation of the available information related to the effective
population size of wolverines in the contiguous United States, recent
trapping/harvest in Canada, and genetic connectivity of wolverines
between the United States and Canada. We are not aware of any new
estimates of effective population size for wolverines in the contiguous
United States; therefore, the N<INF>e</INF> estimate of the wolverine
population in the Northern Rocky Mountains (35) provided by Schwartz et
al. (2009) represents the best available scientific information
regarding effective population sizes in the U.S. portion of the
Northern Rocky Mountains (Service 2023, p. 27). In the 2023 wolverine
SSA report addendum, we estimated the effective population size of the
wolverine population in the North Cascade Mountains, resulting in an
estimate of N<INF>e</INF> = 4 (Service 2023, p. 27). When viewed in
isolation, the overall effective population sizes for wolverines in the
contiguous United States are under the conservation thresholds for
short- and long-term genetic health (50 and 500, respectively). New
information suggests recent trapping harvest in southwestern Canada
resulted in population declines in some areas that may be important
sources of dispersing individuals to the contiguous United States
(Service 2023, pp. 41-42). Furthermore, new information shows that
female wolverine movement is influenced by major transportation
corridors and that the Trans-Canada Highway could be an impediment to
female movement (Service 2023, p. 28). Overall, the effective
population size estimates of wolverines in the contiguous United States
are small
[[Page 83743]]
compared to conservation rules-of-thumb and presumably smaller than the
effective population size of wolverines in Canada. Only one or two
migrants per generation are likely needed to achieve genetic population
connectivity (Cegelski et al. 2006, p. 13); however, based on new
information on gene flow and dispersal, we cannot assume this level of
immigration from Canada is occurring. The contiguous U.S. population
may be at risk of impacts from low effective population size without
sufficient gene flow with Canada. We now conclude that the difference
in effective population size on the U.S. side of the international
border results in a significant difference in conservation status in
light of section 4(a)(1)(D) of the Act as it applies to discreteness.
Habitat Fragmentation--In our December 14, 2010, 12-month finding
(75 FR 78030) and February 4, 2013, proposed listing rule (78 FR 7864),
we stated that wolverine habitat in the contiguous United States
consists of small, isolated areas of high-elevation habitat separated
from each other by low valleys of unsuitable habitat. We also described
that these `habitat islands' are represented by areas containing spring
snow, citing Copeland et al. (2010). We concluded that the fragmented
nature and distribution of wolverine habitat in the contiguous United
States results in a population that is highly vulnerable to extirpation
because of lack of connectivity between subpopulations, and this also
makes them more vulnerable to external threats (75 FR 78030; December
14, 2010). This was used to support our justification for discreteness.
The breeding range of wolverines in the contiguous United States
largely exists in high-elevation alpine forested habitats. Those alpine
areas with established wolverine home ranges are separated by expanses
of lower elevation valley habitats that are not conducive to wolverine
home range establishment but do provide varying levels of connectivity
between home ranges or subpopulations. In Canada and Alaska, habitats
are more contiguous and much less fragmented than wolverine habitat in
the contiguous United States. The fragmented nature and distribution of
wolverine habitat in the contiguous United States puts wolverines
occurring in the contiguous United States at higher risk of impacts
from climate change and other stressors compared to wolverines
occurring in Canada and Alaska. We conclude that the difference in
habitat fragmentation on the contiguous U.S. side of the international
border results in a significant difference in conservation status in
light of section 4(a)(1)(D) of the Act as it applies to discreteness.
Discreteness Based on the International Border--Differences in
Regulatory Mechanisms
Wolverines are currently protected under various State regulatory
designations in the States where the species occurs in the western
United States (Service 2023, table 10). In Canada, provincial
designations for the wolverine include endangered in Labrador, and
threatened in Ontario and Qu[eacute]bec (``threatened'' is equivalent
to endangered in Qu[eacute]bec), with the remaining provincial
designations ranging from no ranking to sensitive or special concern to
the Vancouver Island population's designation as imperiled (COSEWIC
2014, p. 44).
Current regulatory mechanisms prohibit trapping or harvest of
wolverines in the contiguous United States, while trapping is legal in
Canada and occurs in parts of the range that could be a source of
important dispersers to the contiguous United States. We acknowledge
that there is currently a trapping moratorium in a portion of British
Columbia resulting from studies showing population declines in that
area related to trapping (Service 2023, pp. 44-45). However, that
moratorium is temporary and only covers a portion of the Canadian range
(e.g., it does not include Alberta). As discussed above, there are
significant differences in control of exploitation that may be impeding
movement of wolverines, from Canada to the contiguous United States. We
conclude that there are differences in regulatory mechanisms related to
control of exploitation between the United States and Canada that are
significant in light of section 4(a)(1)(D) of the Act.
Discreteness Conclusion
Based on our updated analysis described above and supported by
information in the wolverine SSA report and the wolverine SSA report
addendum, the contiguous U.S. population of the North American
wolverine meets the discreteness criterion in our DPS policy (61 FR
4722; February 7, 1996). It is delimited by the international boundary
with Canada, given differences in control of exploitation, conservation
status, and regulatory mechanisms that are significant in light of
section 4(a)(1)(D) of the Act. After determining that a vertebrate
population is discrete, we are required to complete an analysis to
determine if the population in question is significant according to our
DPS policy; that analysis follows.
Analysis of Significance
If we determine a population segment is discrete, its biological
and ecological significance will then be considered in light of
Congressional guidance that the authority to list DPSs be used
sparingly while encouraging the conservation of genetic diversity. In
carrying out this examination, we consider available scientific
evidence of the population's importance to the taxon to which it
belongs (i.e., the North American wolverine). Our DPS policy states
that this consideration may include, but is not limited to: (1)
persistence of the discrete population segment in an ecological setting
unusual or unique for the taxon; (2) evidence that loss of the discrete
population segment would result in a significant gap in the range of
the taxon; (3) evidence that the discrete population segment represents
the only surviving natural occurrence of a taxon that may be more
abundant elsewhere as an introduced population outside its historical
range; or (4) evidence that the discrete population segment differs
markedly from other populations of the species in its genetic
characteristics. Below, we address considerations 1, 2, and 4.
Consideration 3 does not apply to the continental U.S. wolverine
population because North American wolverines are distributed widely
across Alaska and Canada.
In our December 14, 2010, 12-month finding (75 FR 78030), we
conducted an exhaustive analysis of the significance of the contiguous
U.S. population of the North American wolverine; this analysis was
incorporated by reference into our February 4, 2013, proposed listing
rule (78 FR 7864). In the analysis, we concluded that the wolverine
population in the contiguous United States is significant because its
loss would result in a significant gap in the range of the taxon. In
our October 13, 2020, withdrawal document (85 FR 64618), we did not
present an assessment of significance under the DPS policy because, at
that time, we determined that the wolverine population in the
contiguous United States was not discrete, and thus there was no need
to assess significance. Because we have now determined the wolverine
population in the contiguous United States is discrete, we reviewed and
present an update to our 2010 and 2013 assessment of the significance
of the wolverine population occurring in the contiguous United States
using the best available information.
[[Page 83744]]
Unusual or Unique Ecological Setting
Wolverines occupy a variety of habitats within North America,
including Arctic tundra, subarctic-alpine tundra, boreal forest, mixed
forest, redwood forest, and coniferous forest (Banci 1994, p. 114).
Wolverines in the contiguous United States exist in an ecosystem that
includes high-elevation, remote, rugged, alpine forested terrain and
non-forested habitats around the tree line that retain snowpack into
the spring. The ecoregions inhabited by wolverines in the contiguous
United States are also present in large portions of their occupied
range in Canada and Alaska (Service 2018, appendix A).
Wolverines in the contiguous United States appear to use habitat
attributes that are similar to wolverine populations in Canada and
Alaska, where wolverines also use alpine habitats, and do not appear to
exist in an unusual or unique ecological setting. Thus, we again do not
rely on this factor when determining that the wolverine in the
contiguous United States is significant to the taxon as a whole.
Significant Gap in the Range of the Taxon
Wolverines once lived throughout the North American Rocky Mountains
from Alaska and Canada, south through Colorado and into New Mexico, and
in the North Cascades of Washington and the Sierra Nevada Range of
California. During the late 1800s and early 1900s, the wolverine
population declined or was extirpated in much of the contiguous United
States (Service 2018, p. 1). Wolverines have since recolonized parts of
the contiguous United States, and the current breeding range includes
the Southern Rocky Mountains of Idaho, Montana, and Wyoming and the
Cascades of Washington (Service 2023, figure 3). Individual wolverines
have been documented in California, Colorado, Oregon, and Utah;
however, breeding populations are not known to exist in these areas.
The contiguous United States represents the southernmost extent of the
wolverine's range in North America.
Our significance determination in the December 14, 2010, 12-month
finding (75 FR 78030) concluded that the loss of wolverines in the
contiguous United States would result in a significant gap in the range
of the taxon. This determination was based on an estimate of the
historical range (not current range) of wolverine in the contiguous
United States. This relied on a latitudinally-based interpretation of
historical range in the contiguous United States, the majority of which
was unoccupied at the time the estimation was made and remains
unoccupied by wolverines. We stated in 2010 that the loss of the
population in the contiguous United States would be significant because
it would substantially curtail the range of the wolverine by moving the
southern range terminus approximately 15 degrees latitude to the north
(or approximately 40 percent of the presumed latitudinal extent of the
wolverine's range in North America). For reference, the U.S. border
with Canada is 49 degrees North latitude. Fifteen degrees south of the
border (at 34 degrees North latitude), the assumed 15-degree gap in
latitude (49 degrees North minus 34 degrees North) presented in the DPS
analysis in the December 14, 2010, 12-month finding (75 FR 78030),
lands on 34 degrees North latitude, which runs through western States,
including southern California and approximately the middle of Arizona
and New Mexico, significantly south of the currently occupied range of
wolverine in United States.
During the development of our 2018 wolverine SSA report and 2023
SSA report addendum, we conducted an extensive analysis of the recent
and historical occurrence records for wolverines in the contiguous
United States (Service 2018, pp. 12-16; Service 2023, pp. 3-14). Our
updated significance analysis is based on an updated, spatially
explicit assessment of the current range of wolverines in the
contiguous United States. We used the current range (Service 2023,
figure 2) to provide a more accurate reflection of the range currently
being used by populations of wolverines in the contiguous United States
supported by the best available information. By focusing on the current
range, and not the historical range, we avoid including large sections
of the western United States that do not have high-quality wolverine
habitat (southern California and northern Arizona and New Mexico) in
our significance analysis, and thus we are able to better assess the
significance of the population in the contiguous United States relative
to the larger taxon. The current range of wolverines in the contiguous
United States covers approximately 58,998,140 acres (238,757 km\2\) of
high-quality wolverine habitat with recent wolverine occurrences (from
2009-2023) (Service 2023, figure 2), the loss of which would move the
southern range terminus approximately 12 degrees latitude to the north.
Furthermore, the southernmost portion of the range may be important
for conservation, as it may allow for unique adaptive potential in the
face of a changing global climate and future reduction in cold and
snowy conditions. Populations on the periphery of species' ranges tend
to be given lower conservation priority because they are thought to
exist in low-quality habitats and are also thought to be the
populations that are least likely to survive a reduction in range (Wolf
et al. 1996, p. 1147). However, this tendency presumes that the
ultimate cause of the species' extinction will be one that operates by
eroding away the species' range beginning at the periphery and
progressing to the center. This presumption is based on biogeographical
information that habitat and population densities of species are
highest near the center of the species' range and decline near the edge
(Brown and Lomolino 1998, figure 4.16). Data from documented range
collapses of species from around the world, however, illustrate that
species' ranges tend to collapse to peripheral areas rather than to the
center of their historical ranges (Lomolino and Channell 1995, p. 342;
Channell and Lomolino 2000, pp. 84-86). Of 96 species whose last
remnant populations were found either in the core or periphery of their
historic ranges (rather than some in both core and periphery), 91 (95
percent) of the species were found to exist only in the periphery, and
5 (5 percent) existed solely in the center (Channell and Lomolino 2000,
p. 85). Available scientific data support the importance of peripheral
populations for conservation (Fraser 1999, entire; Lesica and Allendorf
1995, entire).
Based upon the loss of approximately 58,998,140 acres (238,757
km\2\) of high-quality wolverine habitat from the southern extent of
the range and the adaptive potential that part of the range may provide
against oncoming climate change impacts, and a 12 degree latitudinal
gap in the North American wolverine's range that would result if the
U.S. population was lost, we determine that the loss of the contiguous
U.S. wolverine population would result in a significant gap in the
range of the taxon. Thus, the DPS meets the definition of significant
in our DPS policy.
Marked Genetic Differences
In the contiguous United States, small, isolated wolverine
populations are likely dependent on gene flow from Canada for
population persistence (Cegelski et al. 2006, pp. 208-209; McKelvey et
al. 2014, entire). In the Northern Rocky Mountains, the best available
genetic data indicate genetic
[[Page 83745]]
structuring of populations despite some dispersal (Cegelski et al.
2006, pp. 204-205, 208; Sawaya et al. 2023, pp. 12-14). Genetic
structuring reflects the amount of interbreeding between different
groups of an organism where more structure indicates less interaction
between groups, increased genetic isolation, increased potential for
inbreeding, and lower genetic diversity. Given the relatively recent
recolonization of wolverines in the contiguous United States from
Canada (within the last 60-70 years), nuclear genetic diversity was
lower in the southern periphery of the subspecies' range in the south
(Sawaya et al. 2023, pp. 9-11). Nuclear DNA analyses indicated
differences in allele frequencies between the United States and Canada
along the Rocky Mountains, with some areas of overlap in wolverine
populations straddling the border due to male-mediated gene flow.
Females appear to be segregated near the international border due to
their higher rates of philopatry (the tendency of an animal to remain
in or return to the area of its birth) than males and their apparently
greater tendencies to avoid crossing major roadways, including the
Trans-Canada Highway (Highway 1) and the Crowsnest Highway (Highway 3)
in southern British Columbia (Sawaya et al. 2023, pp. 12, 17). Both
highways were opened in the 1960s (British Columbia Ministry of
Transportation and Highways 2001, pp. 16, 20). Since then, they have
been widened in many areas, and traffic volumes have substantially
increased (British Columbia Ministry of Transportation and Highways
2001, pp. 7-11, 16-21). Mitochondrial DNA patterns in the Rocky
Mountains showed no unique contemporary maternal lineages detected
south of the international border, which is consistent with
observational data indicating that wolverines recolonized the
contiguous United States from Canada within the last 60-70 years
(Sawaya et al. 2023, pp. 2, 16-17). Substantially lower mitochondrial
DNA diversity in the United States, as compared to mitochondrial DNA
diversity in Canada, is consistent with the nuclear DNA signals of
limited contemporary female gene flow between the countries along the
Northern Rocky Mountain range and the wolverine's relatively recent
recolonization at the southern edge of their range (Sawaya et al. 2023,
p. 17).
In the North Cascades, global positioning system (GPS) tracking
data show that wolverines in western Washington and southern British
Columbia form a small transboundary population (Aubry et al. 2023, p.
4). Preliminary results from a large population genetics study of this
transboundary population show that wolverines in the North Cascades are
genetically isolated from other wolverine populations in the United
States and Canada and likely went through a genetic bottleneck with few
founders (Sawaya 2023, pers. comm.). The population has low
heterozygosity (less than 0.5) and could be experiencing some level of
inbreeding (Sawaya 2023, pers. comm.). However, there are no
indications or evidence that individuals or population dynamics are
being adversely affected by inbreeding depression (Sawaya 2023, pers.
comm.).
As part of the multi-State wolverine occupancy surveys in 2016-
2017, researchers obtained 240 wolverine DNA samples (Lukas et al.
2020, p. 846). These samples represented 26 unique females and 24
unique males (Lukas et al. 2020, p. 846). Analyses of the mitochondrial
DNA control region revealed regional structuring (i.e., regional
grouping), with all of the samples in Idaho, Montana, and Wyoming
assigned to Haplotype Wilson A (the most abundant haplotype in North
America) and all of the samples in Washington assigned to Haplotype
Wilson C (Lukas et al. 2020, p. 846). These results are consistent with
the latest genetic analysis from the large transboundary study (Sawaya
et al. 2023, entire) and previous mitochondrial DNA studies showing
that the Northern Rocky Mountains and North Cascades do not appear to
share any contemporary haplotypes (McKelvey et al. 2014, p. 328).
The genetic differences between the contiguous United States and
Canada consist of lower genetic diversity in the United States, a
difference that is a reflection of the recent recolonization of
wolverines into the contiguous United States from Canada over the last
century. There are no unique haplotypes present in contiguous U.S.
wolverines that are not already present in larger populations in Canada
and Alaska. As we noted in our analysis in the December 14, 2010, 12-
month finding (75 FR 78030), this is not the kind of genetic difference
that would lead us to conclude that a population is significant under
our DPS policy. The DPS policy is designed to ensure the protection of
important components of a species' evolutionary legacy rather than
populations that simply have lower genetic diversity due to recent
recolonization from a larger source population. Therefore, as in our
2010 analysis, we do not find marked genetic differences as a basis for
determining significance for this DPS.
Summary for Significance
We evaluated whether the discrete population segment of wolverines
in the contiguous United States is also significant, considering
factors such as whether the population segment is in an ecological
setting unusual or unique for the taxon; whether the loss of the
discrete population segment would result in a significant gap in the
range of a taxon; whether the discrete population segment represents
the only surviving natural occurrence of a taxon that may be more
abundant elsewhere as an introduced population outside its historical
range; or whether the discrete population segment differs markedly from
other populations of the species in its genetic characteristics. We
conclude that the wolverine population in the contiguous United States
is significant because its loss would result in a significant gap in
the range of the taxon.
DPS Conclusion
Based on the best available information, we conclude that the
population of wolverines in the contiguous United States is discrete
and significant in relation to the remainder of the subspecies in North
America. As a result, the population of wolverines in the contiguous
United States is a listable entity under section 3(16) of the Act.
The DPS policy sets forth a three-step process for determining
whether a vertebrate population as a separate entity warrants listing:
(1) Determine whether the population is discrete; (2) if the population
is discrete, determine whether the population is significant to the
taxon as a whole; and (3) if the population is both discrete and
significant, then evaluate the conservation status of the population to
determine whether it is endangered or threatened. We have determined
that wolverines in the contiguous United States qualify as a DPS and,
therefore, are a listable entity. Below, we provide a status
determination of the wolverine DPS in the contiguous United States.
Summary of Biological Status and Threats
In this discussion, we review the biological condition of the DPS
and its resources, and the threats that influence the DPS's current and
future condition, in order to assess the DPS's overall viability and
the risks to that viability.
In preparing the 2018 wolverine SSA report and the 2023 SSA report
addendum, we reviewed available reports and peer-reviewed literature,
incorporated survey information, and
[[Page 83746]]
contacted species experts to collect additional unpublished information
for the North American subspecies (Gulo gulo luscus). We identified
uncertainties and data gaps in our assessment of the current and future
status of the subspecies. We also evaluated the appropriate analytical
tools to address these gaps, consulted with species experts, prepared
updated maps of the known subspecies' distribution and breeding range
in the contiguous United States, and evaluated new models of spring
snow. In some instances, we used publications and other reports
(primarily from Fenno-Scandinavia) of the Eurasian subspecies (G. g.
gulo) as a surrogate in completing our status assessment.
Since the publication of the October 13, 2020, withdrawal document
(85 FR 64618), more than 180 new publications have been issued (see
list of citations in the 2023 wolverine SSA report addendum). This is a
substantial amount of new information for a difficult-to-study animal
like the wolverine and has added significantly to our understanding of
wolverine biology. This new information has also highlighted new
insights into the subspecies' biological needs, threats, and the
wolverine's interactions with abiotic and biotic habitat features.
We also conducted an updated geospatial analysis to map verified
wolverine occurrences and approximate breeding ranges in the contiguous
United States. This was informed by recent multi-State monitoring data
(Lukas et al. 2020, entire; Mosby et al. 2023, entire).
Our updated analyses, since the publication of the October 13,
2020, withdrawal document, of the current and predicted future
condition for the wolverine is presented in the wolverine SSA report
addendum and summarized here. Our future-condition analysis includes
the potential conditions that the subspecies or its habitat may face in
the future. This includes consideration of threats most likely to
impact the subspecies at the population or rangewide scales in the
future, including potential cumulative impacts. The spatial expansion
to our climate analysis is a major improvement from the snow
projections used in our 2018 SSA report, which focused only on Rocky
Mountain National Park (Colorado) and Glacier National Park (Montana).
We now focus on five modeling domains that overlap with occupied and
potential wolverine habitat in the contiguous United States across
latitudinal, longitudinal, and elevation gradients. These include: (1)
Cascades (Washington); (2) Northern Rocky West (Washington, Idaho, and
Montana); (3) Northern Rocky (Idaho and Montana); (4) Mid-Rocky (Idaho,
Montana, and Wyoming); and (5) Southern Rocky (Colorado and New Mexico)
(Service 2023, p. 49). In our updated climate assessment, we use a
timeframe out to end of century for assessing future effects to North
American wolverine viability from climate change and other threats.
Beyond 2100, climate modeling uncertainty increases substantially. Our
previous assessment considered in the October 13, 2020, withdrawal
document (85 FR 64618) looked at a timeframe 50 years into the future.
We conclude that end of century is a reasonable timeframe, as it
includes the potential for observing these effects over several
generations of the wolverine.
As discussed above in Analytical Framework, we consider what the
subspecies needs to maintain viability by characterizing the status of
the subspecies in terms of resiliency, redundancy, and representation
(Wolf et al. 2015, entire). Resiliency is having sufficiently large
populations for the subspecies to withstand stochastic events (arising
from random factors). We can measure resiliency based on metrics of
population health (for example, birth versus death rates and population
size). Resilient populations are better able to withstand disturbances
such as random fluctuations in birth rates (demographic stochasticity),
variations in rainfall (environmental stochasticity), or the effects of
anthropogenic activities.
Redundancy is having a sufficient number of populations for the
subspecies to withstand catastrophic events (such as a rare destructive
natural event or episode involving many populations). Redundancy is
about spreading the risk and can be measured through the duplication
and distribution of populations across the range of the subspecies. The
greater the number of populations a subspecies has distributed over a
larger landscape, the better it can withstand catastrophic events.
Representation is having the breadth of genetic makeup of the
subspecies to adapt to changing environmental conditions.
Representation can be measured through the genetic diversity within and
among populations and the ecological diversity (also called
environmental variation or diversity) of populations across the
subspecies' range. The more representation, or diversity, a subspecies
has, the more it is capable of adapting to changes (natural or human-
caused) in its environment. In the absence of subspecies-specific
genetic and ecological diversity information, we evaluate
representation based on the extent and variability of habitat
characteristics within the geographical range.
Life-History Needs
Wolverine populations are characterized by naturally low densities.
The species is highly territorial, with very little overlap between
same-sex adults. Wolverines occupy a variety of habitats, but generally
select habitat in locations away from human settlements and activities.
The wolverine is a snow-adapted, cold-climate animal in its physiology
and morphology (Telfer and Kelsall 1984, p. 1830); phylogeography
(historical processes that may be responsible for past and present
geographic distributions of genealogical lineages); and behavior and
habits (Fisher et al. 2022, p. 7).
Wolverines consume a variety of food resources, and seasonal
switching of prey is commonly observed. Unlike wolverine populations in
Eurasia, wolverines in the contiguous United States rarely prey on
livestock. During our extensive literature review in preparing the 2023
wolverine SSA report addendum, we discovered only two instances of
wolverine depredation in the United States since our 2018 SSA report;
one wolverine that had depredated sheep in Utah, and another that was
caught in a chicken coop in Washington (Service 2023, pp. 10, 38).
Wolverine reproduction includes the following characteristics:
polygamous behavior (i.e., male mates with more than one female each
year), delayed implantation (up to 6 months), a short gestation period
(30-40 days), denning behavior (only observed in snow in the contiguous
United States), and several additional months of maternal care (Service
2018, p. 22). The reproductive behavior in wolverines is temporally
adapted to take advantage of the availability of food resources,
limited interspecific competition, and snow cover in the winter.
In our 2018 wolverine SSA report, we defined the physical and
ecological requirements of wolverine in the contiguous United States
(see (1), (2), and (3), below). In light of new information regarding
wolverine habitat associations that provides support for the
wolverine's strong preference for areas with cold and snowy conditions,
we have added a fourth ecological requirement (see (4), below). The
requirements are:
(1) Large territories in relatively inaccessible landscapes, at
high elevation (1,800 to 3,500 m (5,906 to 11,483 ft));
[[Page 83747]]
(2) Access to a variety of food resources that vary with seasons;
(3) Physical/structural features (e.g., talus slopes, rugged
terrain) linked to reproductive behavioral patterns; and
(4) Habitats characterized by the presence of persistent spring
snow (of greater than or equal to 1 meter on May 1) for survival and
reproduction.
Our 2023 wolverine SSA report addendum affirms these requirements
and the species characterization in our 2018 SSA report.
Habitat
Research published since our 2018 wolverine SSA report confirms
that broad-level habitat selection (subspecies' range, individual home
range) at the southern edge of the wolverine's distribution can be
accurately predicted using a small number of high-elevation variables
and terrain features (Carroll et al. 2021a, pp. 1470-1471; Aubry et al.
2023, p. 7). New evidence from around the world reinforces that snow--
especially persistent spring snow--is an important predictor of broad-
scale wolverine distribution and density (Aubry et al. 2023, pp. 15-16;
Carroll et al. 2020, p. 8; Fisher et al. 2022, p. 10; Glass et al.
2021, entire; Mowat et al. 2020, p. 220). Within home ranges, the
precise nature of the relationship between wolverine space-use and snow
is complex, involving multiple snow characteristics (e.g., density,
depth, and melt), various phases of the wolverine lifecycle (e.g.,
denning, feeding and food caching, within-territory movements, and
dispersal) and sex-specific habitat selection (Carroll et al. 2021, p.
1469; Glass et al. 2021, entire; Heinemeyer et al. 2019, p. 16). While
wolverines appear capable of occupying and reproducing in areas without
persistent spring snow in some ecological contexts, at a continent-wide
scale, wolverine dens outside of areas with persistent spring snow have
thus far only been documented to occur in colder boreal or arctic
environments in Canada and Alaska (Aronsson and Persson 2017, p. 266;
Copeland et al. 2010, pp. 240-242; Fisher et al. 2022, p. 8; Jokinen et
al. 2019, pp. 6-8; Webb et al. 2016, pp. 1466-1467).
In the Greater Yellowstone Ecosystem, distance to high-elevation
talus, snow water equivalent (a surrogate for snow depth), and
latitude-adjusted elevation were the most important environmental
factors explaining selection of wolverine home ranges and habitats
within home ranges (Service 2023, p. 16). These habitat variables are
also known to be important in defining the wolverine's distribution
(Inman et al. 2013, p. 278).
Results from dispersal suitability models developed for wolverines
indicate that isolation by landscape resistance (areas that individuals
are less likely to traverse due to high energy, mortality, or other
biological costs) explained more of the variation in wolverine genetic
differences than did isolation by distance (Balkenhol et al. 2020, pp.
795-797). This means that wolverines are moving non-randomly across the
landscape in association with specific landscape features. Snow depth
(average 1-year snow depth at 1-km\2\ resolution), terrain ruggedness
(measure of how jagged or flat the terrain is on average), and housing
density (census block housing density per 1 km\2\) best predicted gene
flow in wolverines (Balkenhol et al. 2020, pp. 795-797). Snow depth was
the most important variable for explaining variation in genetic
differences overall (Balkenhol et al. 2020, p. 790). At broad spatial
scales, housing density and terrain ruggedness were the most important
factors, where wolverines avoided areas of high housing density and
preferred areas of terrain ruggedness, which explains the variation in
wolverine genetic differences (Balkenhol et al. 2020, p. 790).
In the Cascade Range in southern British Columbia and Washington,
three climatic variables (proximity to the transitional zone near the
alpine tree line, number of frost-free days per year, and annual
precipitation as snow) were correlated with wolverine location data
(Aubry et al. 2023, p. 10). Wolverine distribution in the Cascades is
constrained by climatic conditions; snowy, cold environments delimit
the areas that are ``overwhelmingly associated with resident
wolverines'' (Aubry et al. 2023, p. 16). The highest-use areas were on
the eastern side of the Cascades, where alpine habitats had fewer
frost-free days (Aubry et al. 2023, p. 15). This is consistent with
other models, indicating that wolverines rely on the transitional zone
between the tree line, below which environmental conditions become too
warm, and upper elevations of permanent ice and snow, where there is
insufficient food and cover to support basic life-history requirements
for wolverines (Aubry et al. 2023, pp. 13-14).
A study using GPS location data on 38 wolverines from 2001 to 2010
analyzed wolverine home range habitat selection across the western
United States by identifying landscape variables that were highly
correlated with wolverine home ranges (Carroll et al. 2020, entire).
The resource selection function model included landform (e.g., ridges
and peaks), vegetation classification, distance to high-elevation
talus, latitude-adjusted elevation, average monthly snow water
equivalent, and human modification (Carroll et al. 2020, p. 8). Core
areas were identified, and connectivity was assessed, between these
core areas using a landscape resistance model, validated with GPS
location data from dispersing wolverines (Service 2023, figure 3).
Results showed that resident wolverines in core habitats are far more
sensitive to low-quality habitat than are dispersing individuals, but
that dispersers still follow lower-resistance pathways that connect
higher quality core habitats (Carroll et al. 2020, p. 9). Another study
modeled within-home range habitat selection by wolverines in areas of
the Northern Rocky Mountains with high amounts of winter backcountry
recreation and found significant differences in male and female habitat
selection (Heinemeyer et al. 2019a, p. 9). The best model for male
wolverines included distance to roads and proportion of lower elevation
grass and shrub cover, while the best model for female wolverines
included talus, persistent spring snow cover (defined in the cited
studies as snow cover present between April 24 and May 15), and forest
edge-to-area covariates (Heinemeyer et al. 2019a, p. 9). Best models
for both sexes included covariates for topographic position index,
quadratic form of slope, distance to forest edge, solar insulation, and
percentage cover of forest, riparian, and montane open cover types.
This study also showed that wolverines are negatively affected by
winter recreation (see Disturbance Due to Winter Recreational Activity,
below).
Multiple recent studies in Canada have provided further evidence of
the influence of snow cover and human development/disturbance on
wolverine distribution. Wolverine density in and around a national park
complex in the southern Canadian Rocky Mountains was three times higher
within these national parks than outside them, increased with spring
snow cover, and decreased with increasing night light intensity (a
measure of human development) (Barrueto et al. 2022, p. 4). Along the
Front Range of the Canadian Rocky Mountains, wolverines selected areas
with natural land-cover and high snow cover and avoided anthropogenic
features and heterospecific competitors (Heim et al. 2019, pp. 2499-
2502). In the Rocky Mountains of Alberta, wolverine occurrence in space
and time was best explained by coyote (Canis latrans) occurrence and
the density of linear
[[Page 83748]]
disturbance features (e.g., roads, pipelines, seismic lines, motorized
and nonmotorized recreational trails), with both of these factors
decreasing the likelihood of wolverine occurrence (Chow-Fraser et al.
2022, pp. 4-5). In the southern Canadian Rockies, wolverine density was
found to be positively correlated with the number of years of
persistent spring snow cover and negatively correlated with road
density (Clevenger 2019, p. 62; Mowat et al. 2020, pp. 218-219). Female
densities in areas with more cumulative years of persistent spring snow
were higher than male densities, which suggests there may be a
preference for snowy areas when denning. An additional study, also in
the Canadian Rockies, found that food availability and human
disturbance were major drivers of wolverine distribution in winter
(Kortello et al. 2019, p. 7). Persistent spring snow was an important
factor in explaining the variation in female wolverine distribution in
winter and overall wolverine distribution at coarse scales (Kortello et
al. 2019, p. 8). The researchers concluded that their results ``do not
reject the hypothesis that wolverine occurrence is constrained by an
obligate association with persistent spring snow'' (Aubry et al. 2007,
p. 2154; Copeland et al. 2010, p. 244), ``but do suggest the
alternative explanation that the relationship between spring snow and
wolverine distribution could be functionally related to the
distribution of food, disturbance or mortality risk'' (Kortello et al.
2019, p. 8). We agree with their assessment and acknowledge the precise
causal mechanism(s) for the apparent association of wolverine
distribution and persistent spring snow are not yet clear. There may be
a number of factors acting in concert to drive the wolverine's
preference for cold and snowy conditions, and we have attempted to
account for this in our analysis presented in this rule.
A habitat selection study of 21 adult, non-denning wolverines (11
female, 10 male) fitted with GPS collars in the Alaskan Arctic found
that wolverines generally selected more rugged areas closer to streams,
rivers, and lakes (Glass et al. 2021, p. 893). This study also showed
that snow characteristics are important to wolverines for reasons other
than solely creating reproductive dens. Specifically, they found that
non-denning wolverines select deeper, denser snow, but only when that
snow is not undergoing melt (Glass et al. 2021, pp. 894-895). The
wolverine's observed preference for denser snow might be a function of
both ease of movement across the surface, as well as the ability of
denser snow to maintain snow cavities and tunnels (Glass et al. 2021,
p. 895).
Denning Habitat--Denning habitat has been a focus for wolverine
conservation because wolverines have naturally low reproductive rates.
Impacts to denning habitat could have important consequences for
demographic rates (Fisher et al. 2022, p. 8). There is growing evidence
that wolverines rely on subnivean space (the environment between snow
and terrain) for thermoregulation, to escape predation risk, and/or to
cache food (van der Veen et al. 2020, pp. 8-10; Fisher et al. 2022, p.
10). Although wolverines have been documented denning in areas without
persistent spring snow (Fisher et al. 2022, p. 8; Persson et al. 2023,
entire), this phenomenon appears to be associated with cold, high-
latitude boreal or arctic forests rather than the alpine habitats used
by wolverines in the contiguous United States. In the contiguous United
States, there is no evidence that wolverines have denned in areas
without persistent spring snow.
Den-shifting behavior represents a tradeoff between moving--and
risking potential energy loss and harm to offspring--versus staying in
the original den site and risking exposure to disturbance or changed
conditions, such as melting snow, that might make the original den site
unsuitable (Heeres 2020, p. 9). In a study in northern Sweden focusing
on 18 adult female wolverines fitted with GPS collars over an 11-year
period and occupying 271 den sites, Heeres (2020, p. 15) determined
that a female used an average of 12 den sites during a single denning
season (range: 4-28; median: 10). Additionally, female wolverines had a
higher probability of shifting den sites in forested habitats, compared
to alpine habitats, which is likely a result of earlier snow melt in
forests that may make den sites uninhabitable early in the season
(Heeres 2020, p. 20). Other factors related to den-shifting behavior
included the level of denning experience of the female wolverine, which
was quantified as the number of previous reproductive attempts by an
individual (lower den-shift probability), temperature (higher den-shift
probability in the warmer forested habitats; nonsignificant den-shift
probability in alpine habitat), food resource availability (higher den-
shift probability, which could be related to accessing food or
increased human presence), and cub age (more shifting as cubs mature
and are able to move to food resources) (Heeres 2020, pp. 20-22).
In certain ecological contexts, individual wolverines and
reproductive dens can exist in areas without substantial spring
snowpack (Persson et al. 2023, p. 10; Jokinen et al. 2019, pp. 4-9).
For example, Jokinen et al. (2019, pp. 6, 10) observed seven of eight
wolverine dens (three primary and five secondary dens) in hollows of
uprooted trees and not in snow; however, the researchers acknowledged
that sample sizes were small and limited their ability to draw robust
conclusions. Jokinen et al. (2019, p. 12) speculated that wolverines,
in the absence of spring snow in Alberta, were able to meet their
physiological needs through locally available features such as the
cavity created by partially uplifted root masses, the thermal
properties of thick moss, and the caching opportunities provided by
deep peat accumulations. Wolverines are resourceful and may be more
flexible in their denning requirements than documented by studies in
other landscapes (Persson et al. 2023, p. 10; Jokinen et al. 2019, p.
12; Glass et al. 2021, entire); however, it is also apparent that
boreal forest communities have a series of unique properties conducive
to wolverine denning, including cold spring temperatures and dense peat
layers that might aid in insulating the den (Jokinen et al. 2019, p.
12).
At present, it remains uncertain whether the alpine ecosystems in
the contiguous United States contain environmental conditions that
would allow wolverines to switch denning behavior or use smaller or
shallower patches of snow in response to changes in future snow under a
changing climate. Even if they were able to make this shift, snow may
be important to wolverines for more than just denning.
Food Caching--Wolverines are physiologically and behaviorally
adapted to caching perishable food in snow, boulders, and peat bogs for
short- or long-term storage (van der Veen et al. 2020, pp. 2-3). In
Scandinavia, wolverines cached food all year from scavenging and
predation events, with the locations of food caches widely distributed
across their home ranges (van der Veen et al. 2020, pp. 6-8). When
caching, wolverines selected steep and rugged terrain in unproductive
habitat types (habitats with fewer plants and animals) or in forest,
indicating a preference for less-exposed sites that can provide cold
storage or protection against pilferage. The observed year-round
investment in caching by wolverines suggests that food predictability
is important for their
[[Page 83749]]
survival and reproductive success. Increasing temperatures caused by
climate change may provide new challenges for wolverines in at least
two ways: (1) by decreasing the shelf-life of cached food, and (2) by
increasing competition from pilferers that benefit from a warmer
climate (van der Veen et al. 2020, pp. 8-10).
Areas of Uncertainty for Wolverine Habitat Needs
The precise causal mechanism(s) for the apparent association of
wolverine distribution and persistent spring snow are not yet clear.
Hypotheses for this association include the importance of snow to
create dens (Copeland et al. 2010, entire), the advantages of snow for
catching prey within a wolverine's metabolic limits (Young et al. 2012,
pp. 224-226), competitive advantages over other scavengers and
predators in snow-covered areas (Service 2018, p. 6), thermoregulation
(Service 2018, pp. 7-8), food storage and refrigeration (Inman et al.
2012, p. 640), or some combination of these factors. The interplay of
temperature and persistence of spring snow and the point at which
temperature becomes limiting is also unknown.
There is presumably some limit in appropriate habitat availability
at which wolverines will not cross certain habitats or traverse certain
barriers, but that threshold is not known. Understanding this threshold
for females is particularly important because they often disperse
shorter distances than males and appear to be more affected by
potential barriers to movement, such as large multi-lane highways
(e.g., Sawaya et al. 2019, pp. 621-623).
Recent studies from Canada and Alaska have shown that apex
predators and sympatric mesocarnivores (small to mid-sized carnivores
that occur in the same area) can influence wolverine space use (e.g.,
Heim et al. 2019, pp. 2499-2504; Frey et al. 2020, pp. 1133-1137; Bell
2021, pp. 46-47; Klauder et al. 2021, p. 569; Chow-Fraser et al. 2022,
p. 4). In addition, it is possible that competitors such as coyotes
that thrive within human-dominated landscapes could potentially
displace wolverines in areas with substantial anthropogenic disturbance
(Chow-Fraser et al. 2022, pp. 4-5). However, the influence of apex
predators and intraguild competition on wolverine distribution,
abundance, and dispersal in the contiguous United States remains
largely unstudied.
Threats
A species may be determined to be an endangered or threatened
species due to one or more of the five factors described in section
4(a)(1) of the Act: (A) The present or threatened destruction,
modification, or curtailment of its habitat or range; (B)
overutilization for commercial, recreational, scientific, or
educational purposes; (C) disease or predation; (D) the inadequacy of
existing regulatory mechanisms; or (E) other natural or manmade factors
affecting its continued existence. Listing actions may be warranted
based on any of the above threat factors, singly or in combination.
Threats evaluated for the wolverine in the contiguous United States
include climate change (Factors A and E), effects from roads (Factors A
and E), disturbance due to winter recreational activity (Factors A and
E), other human disturbance (Factors A and E), effects from wildland
fire (Factor A), disease (Factor C), predation (Factor C),
overutilization (trapping) (Factor B), genetic diversity (Factor E),
and small population effects (Factor E). We found that habitat loss as
a result of climate change is the primary threat to the wolverine's
future viability in the contiguous United States. We expect climate
change to exacerbate effects from multi-lane roads, backcountry winter
recreation, and human development, all of which could then impact
genetic diversity and small population dynamics. A summary of the
threats affecting the North American wolverine in the contiguous United
States is presented below; for a full description of our evaluation of
the effects of these stressors, refer to the wolverine SSA report
(Service 2018, pp. 57-101) and the 2023 wolverine SSA report addendum
(Service 2023, pp. 30-47).
Climate Change: The wolverine's evolutionary and phylogeographic
history suggest a species adapted to cold and snowy climate conditions
(Fisher et al. 2022, p. 7; Service 2023, pp. 24-25). The wolverine is a
snow-adapted, cold climate animal in its physiology, morphology (Telfer
and Kelsall 1984, p. 1,830), behavior, and habits. Wolverines have been
classified as a ``chionphile'' or those animals with adaptations for
snow (e.g., increased surface area on feet, pelt characteristics) (see
definitions in Pruitt 1959, p. 172; Cathcart 2014, p. 22). We find that
impacts from climate change (increasing temperatures and decreasing
snowpack) have the largest potential to influence the North American
wolverine's population viability in the future.
To inform our assessment of the North American wolverine's status
in the contiguous United States, we updated our previous climate change
analysis, the details of which are summarized in the wolverine SSA
report addendum (Service 2023, pp. 47-59). The spatial expansion to our
climate change analysis is a major improvement from the snow
projections used in our 2018 SSA report, which focused only on Rocky
Mountain National Park (Colorado) and Glacier National Park (Montana).
We now focus on five modeling domains that overlap with occupied and
potential wolverine habitat in the contiguous United States across
latitudinal, longitudinal, and elevation gradients: (1) Cascades
(Washington); (2) Northern Rocky West (Washington, Idaho, and Montana);
(3) Northern Rocky (Idaho and Montana); (4) Mid-Rocky (Idaho, Montana,
and Wyoming); and (5) Southern Rocky (Colorado and New Mexico) (Service
2023, p. 49). Central Idaho was not modeled due to constraints of time
and resources. In our updated climate assessment, we use a timeframe
out to year 2100 for assessing future effects to the North American
wolverine's viability from climate change and other threats. Beyond
2100, climate modeling uncertainty increases substantially due to the
inability to predict human behavior, policy changes, and, by extension,
future greenhouse gas emissions. Our previous assessment in the October
13, 2020, withdrawal document (85 FR 64618) looked at a timeframe of 38
to 50 years into the future. We find that end of century is a
reasonable timeframe to consider, as it includes the potential for
observing these effects and the wolverine's responses over several
generations of the wolverine.
Two scenarios were chosen from the Intergovernmental Panel on
Climate Change (IPCC) Sixth Assessment Report to bracket the
uncertainty regarding future greenhouse gas emission scenarios (Tebaldi
et al. 2021, p. 258). The two emission scenarios used in the analyses
are referred to as SSP2-4.5 and SSP5-8.5; SSPs replace representative
concentration pathways (RCPs) from prior IPCC reports. The numerical
suffixes (e.g., 2-4.5 and 5-8.5) represent the approximate level of
radiative forcing (the change in energy flux in the atmosphere caused
by natural or anthropogenic factors of climate change) in 2100
(compared to preindustrial levels) in units of watts per meter squared
(W/m\2\). The SSP2-4.5 pathway (modest mitigation) used in this
analysis is similar to the RCP 4.5 scenario used in past reports,
whereas the SSP5-8.5 pathway represents one of the most pessimistic
estimates of future greenhouse gas emissions, a future with no
mitigation policy. The SSP5-8.5
[[Page 83750]]
pathway was included in this analysis to provide a lower-boundary
estimate of future snow cover available for wolverines within the
selected domains (OSTP 2023, p. 11). We chose a snow depth threshold of
greater than or equal to 1 m (40 inches) to represent persistent spring
snow cover on May 1 based on published literature, our prior analyses
in the 2018 SSA, and studies indicating that den site abandonment
generally occurs before May 1 (see the Use of Dens and Denning Behavior
discussion in the Reproduction and Growth section of the 2018 SSA
(Service 2018, pp. 25-27). There is no known snow depth threshold for
successful wolverine denning on any date. However, based on historical
den site melt-out dates (when there was no snow at the den sites) and
hindcasted (historical) snow models for Glacier National Park, the 2018
SSA used greater than 0.5 m (20 inches) on May 1. We received criticism
from some wolverine researchers that the use of the 0.5-m snow depth
threshold on May 1 was not conservative enough based on prior studies
(e.g., Copeland et al. 2010, entire; McKelvey et al. 2011, entire) that
considered snow depth out to June. Others would argue (based on the
importance of snow for denning) that snow depth at May 1 is not as
important since young wolverine kits are usually out of their natal
dens by mid-March (Inman 2023, pers. comm.). To address the criticism,
and to acknowledge that snow is likely important to the wolverine for
more life behaviors than just denning, for our updated analysis we
increased the snow depth measure representing persistent snow cover to
greater than or equal to 1 m (3.3 ft) but retained the May 1 end date.
This provides a reasonable but more conservative estimate than we used
in the 2018 SSA.
Results from this updated climate change analysis are consistent
with earlier studies predicting greater snow loss at lower elevations
across all domains. Similar elevational patterns were reported for
Rocky Mountain and Glacier National Parks with greater reductions in
future snow cover at lower elevations (Barsugli et al. 2020, pp. 8-10).
This is partially explained by a greater percentage of future
precipitation falling as rain due to higher temperatures, earlier
snowmelt onset, and warmer conditions. Snowpack in the high country is
not as affected by projected temperature increases but is likely more
strongly controlled by projected precipitation changes (Barsugli et al.
2020, pp. 6-11; Scalzitti et al. 2016, p. 5367; Sospedra-Alfonso et al.
2015, p. 4429).
The elevational distribution of historical den sites varies by
latitude, with a general trend of dens being found at higher elevations
the farther south they are found. For example, dens in the Northern
Rocky domain are found at elevations ranging from approximately 1,500-
2,400 m (4,921-7,874 ft) (Service 2023, figure 12), while dens in the
Mid-Rocky domain are found from approximately 2,400-3,000 m (7,874-
9,843 ft) (Service 2023, figure 13). Additional den sites outside of
the modeling domains could expand these elevational bands. The majority
of historical dens across the domains are located in elevational bands
that are predicted to experience relatively small decreases in future
snow cover at the higher denning elevations and moderate decreases for
lower denning elevations. The percentage change in future snow depth
threshold (greater than or equal to 1 m (3.3 ft)) on May 1 (median) for
SSP2-4.5 (2076-2095) for the upper denning elevations in Northern Rocky
West, Northern Rocky, and Mid-Rocky domains is predicted to be a less
than 10 percent decrease, whereas the percentage change for the
Cascades domain is predicted to be a less than 25 percent decrease. The
percentage change in future snow depth threshold (greater than or equal
to 1 m (3.3 ft)) on May 1 (median) for SSP2-4.5 (2076-2095) for the
lower denning elevations in Northern Rocky is predicted to be a 10-50
percent decrease, and for Mid-Rocky is predicted to be a 10-25 percent
decrease, while the percentage change for the Cascades domain is
predicted to be a less than 25 percent decrease.
Elevations above historical den elevations are predicted to have
small decreases (less than 10 percent) in the future area with snow
depth exceeding the threshold (greater than or equal to 1 m (3.3 ft))
on May 1 (median) for SSP2-4.5 (2076-2095) across the domains and in
some cases (e.g., Northern Rocky and Mid-Rocky domains), there are
increases in predicted future area with snow exceeding the greater than
or equal to 1 m (3.3 ft) May 1 threshold. This is driven by the
increases in future precipitation expected in all five domains, and
elevations with temperatures sufficiently cold enough to sustain
snowfall, even with future warming. The lowest elevation areas within
all domains (the lowest approximately 500 m (1,640 ft) of domains
modeled) are predicted to have the greatest decreases in the future
snow depth threshold (greater than or equal to 1 m (3.3 ft)) on May 1.
For example, the Northern Rocky domain is predicted to experience
decreases of 50 to 100 percent at 1,000-1,500 m (3,281-4,921 ft) of
elevation (Service 2023, figure 13). Similar patterns are seen in the
other four domains, including predicted changes (mostly negative) in
the future snow depth threshold (greater than or equal to 1 m (3.3 ft))
on May 1. While decreases are projected across the domains, the
specific thresholds that could impact wolverine persistence at the
population level are not known.
Central to our assessment of future conditions is the degree to
which changes in persistent spring snow, other snow dynamics (e.g.,
volume, duration, condition, spatial and temporal variability, etc.),
and other climate-related factors will impact wolverines at the
population level in the contiguous United States. Key uncertainties
that remain regarding these relationships include: (1) the extent to
which wolverine population connectivity and gene flow will be affected
by these changes; (2) the impacts of climate change on ecosystem
drivers of wolverine persistence (i.e., changes in community dynamics,
including prey availability and competition with other predators that
might impact wolverine demographic rates); (3) the volume and duration
of snow required for wolverines to successfully acquire and cache food
for future use; (4) the impacts of climate change on the ability of
wolverines to thermoregulate, and whether wolverines might experience
any sublethal effects from changes in temperature (e.g., impacts to
reproduction) (see Thiel et al. 2019, entire); (5) whether the observed
associations of the wolverine's distribution with snowy and cold
environments are driven by reproductive denning needs, other ecological
requirements, or physiological constraints (Aubry et al. 2023, p. 16);
(6) the adaptive capacity of wolverines to move to higher elevations
for denning given predicted snow loss at lower elevations within their
historical denning range (assuming snow is required for denning); and
(7) the importance of snow and the impact of decreases in future snow
within historical denning elevations on reproductive success. In
summary, specific thresholds regarding snow dynamics and how changes in
these factors will impact wolverines in the future at the population
level remain uncertain.
That said, we know that wolverines are a species that is adapted
to, and has a strong preference for, cold and snowy conditions and that
these conditions occur in the contiguous United States at high
elevations. As explained before,
[[Page 83751]]
there are uncertainties as to the exact mechanism(s) by which spring
snowpack is important to wolverines or when it may become limiting.
Although wolverines have been shown to den outside of spring snowpack
in Canada and Scandinavia, we continue to have no evidence of this
behavioral ability in the contiguous United States. Furthermore, new
research on wolverine habitat use continues to reinforce that cold and
snowy conditions are a strong predictor of wolverine occurrence on the
landscape (Aubry et al. 2023, pp. 15-16; Carroll et al. 2020, p. 8;
Fisher et al. 2022, p. 10; Glass et al. 2021, entire; Mowat et al.
2020, p. 220). Furthermore, deep, persistent snow cover has been shown
to be an important predictor of successful wolverine dispersal and
resulting genetic structure (Balkenhol et al. 2020, pp. 798-799). New
research on food caching indicates that warming future conditions could
make caching food, a year-round behavior, more difficult for wolverines
(Van der Veen et al. 2020, pp. 8-10). As climate change reduces the
preferred habitat conditions for wolverine, it has the potential to
exacerbate other stressors discussed above including effects from
roads, winter recreational activity, effects from development, low
genetic diversity, and small population effects. When taken together,
we have no reason to conclude that wolverines will somehow continue to
have the same or better resiliency in the contiguous United States in
the future when those cold and snowy conditions at high elevations are
expected to decrease, with spring snowpack at denning elevations
decreasing as much as 50 percent in some areas. Although we are not
seeing deleterious effects of climate change on the contiguous U.S. DPS
of North American wolverines currently, we expect future impacts at the
population level.
Effects from Roads: In our 2018 SSA and the October 13, 2020,
withdrawal document (85 FR 64618), we concluded that roads present a
low stressor to wolverines at the individual and population level in
most of the wolverine's current area of occupancy within the contiguous
United States. New information on the effects of roads on the North
American wolverine's distribution, density, reproduction, and
connectivity and gene flow are presented below.
Since 2018, we were made aware of four wolverine mortalities from
collisions with vehicles in the contiguous United States, at least
three of which were males (Service 2023, p. 30). Overall, young,
inexperienced male wolverines have a greater risk of road mortality
during dispersal compared to adults and immature females that are less
prone to long-distance dispersal (e.g., Krebs et al. 2004, pp. 497-
498). The small number of mortalities observed since 2018, if biased
toward males, are unlikely to have substantial impacts to the
resiliency of the DPS overall.
New studies available in southwestern Canada and the western United
States since the 2018 SSA have found that North American wolverine
distribution and density are negatively related to road density
(Service 2023, pp. 31-32). In southwestern Canada, consistency of
spring snow and road density are the two most important variables
correlated with wolverine density (Clevenger 2019, p. 52; Mowat et al.
2020, p. 220). Wolverine population estimates derived from models based
on snow and road density predicted that wolverine abundance would be 44
percent higher without the depressing effect of the road covariate
(Clevenger 2019, p. 52; Mowat et al. 2020, p. 220). As most roads are
concentrated in areas of human development at lower elevations with
less snow, correlations between wolverine distribution and road density
can be confounded by other collinear variables (Copeland et al. 2007,
pp. 2210-2211). In southeastern British Columbia, the density of forest
roads that extended into high-elevation wolverine habitat was a strong
negative predictor of wolverine distribution in winter, especially for
females (Kortello et al. 2019, p. 10). The most likely explanation for
this negative relationship is the use of these high-elevation forest
roads by snowmobilers, rather than predator avoidance or trapping
pressure (Kortello et al. 2019, p. 10). Other possible explanations are
increased trapping access or less abundant food resources near roads
(Mowat et al. 2020, p. 224). While the statistical significance of the
relationship between roads and wolverine densities has been
demonstrated in some areas, the mechanisms behind this relationship
require further study (Mowat et al. 2020, p. 224).
Large transportation corridors (e.g., multi-lane highways with
substantial traffic volume) can have a significant impact on wolverine
population connectivity and gene flow. The mechanisms for reducing
connectivity and gene flow are road mortality and reduced habitat
permeability (avoidance of crossing roads). Mitochondrial and nuclear
DNA measures of genetic population structure found that the Trans-
Canada Highway corridor in the Canadian Rockies, as well as other
natural and anthropogenic barriers to movement, fragmented the North
American wolverine population by restricting female movement (Sawaya et
al. 2019, pp. 621-622). This restricted movement resulted in male-
biased dispersal and gene flow (Sawaya et al. 2019, pp. 621-622). This
highway is approximately 150 miles north of the U.S.-Canada border, and
the study area for analyzing wolverine movement across the Trans-Canada
Highway was in the lower Bow River Valley, which is a human-dominated
landscape containing the Trans-Canada Highway, a town with
approximately 10,000 residents, a golf course, three ski areas, the
Canadian Pacific Railway, and a secondary highway. This transportation
corridor was not an absolute barrier to female movement (4 of 20 female
wolverines crossed the highway during the study); however, females
traversing the transportation corridor did not translate to gene flow
(Sawaya et al. 2019, p. 622). The differences between male and female
dispersal across this highway were likely due to the exacerbating
effects of linear anthropogenic barriers on the strong natural
tendencies for female wolverine philopatry (tendency to return to or
remain near a particular area or site) (Sawaya et al. 2019, p. 623).
(See Genetic Diversity, below, for more discussion of the effects of
roads on gene flow and genetics of wolverines within the contiguous
United States and genetic connectivity to Canada).
Wildlife crossing structures spanning the Trans-Canada Highway
along the crest of the Continental Divide may improve wolverine
connectivity across this highway. Evidence suggests that female
wolverines may be starting to use wildlife crossings to cross the
Trans-Canada Highway (Service 2023, p. 32). However, the efficacy of
these structures in restoring gene flow has not yet been measured
(Sawaya et al. 2019, p. 623). There are few wildlife crossing
structures spanning major highways in the contiguous United States; a
series of three under-crossings and one dedicated wildlife overpass on
I-90 in the Washington Cascades (connecting the northern and southern
Cascades) were completed in 2019 (Sugiarto 2022, p. 9). To date,
however, no wolverines have been detected using these relatively new
crossings.
Habitats in the contiguous United States outside of the known
breeding distribution of wolverines, including the Sierra Nevada in
California and the central Rocky Mountains in Colorado, are separated
from occupied habitats by
[[Page 83752]]
large expanses of high-resistance habitats, anthropogenic features, and
highways (e.g., Carroll et al. 2020, pp. 9-10; Bjornlie et al. 2021,
pp. 116-117). While highways are not an absolute barrier to movement
(wolverines have been documented crossing multi-lane highways), they
can apparently limit female wolverine gene flow in some situations
(e.g., Sawaya et al. 2019, pp. 621-622). The wolverine's capacity to
traverse large expanses of high-resistance habitats, anthropogenic
features, and highways and naturally recolonize and establish a
population in some relatively isolated habitats in the contiguous
United States (e.g., Oregon Cascades, Sierra Nevada, and central Rocky
Mountains) remains unclear.
Based on the best available scientific and commercial information,
the effect of roads, in isolation, represents a relatively low threat
to wolverines in the contiguous United States at the population level,
although some individuals are affected. However, in combination with
other threats discussed below, roads, in particular multi-lane, high-
traffic roads, and high road density in core habitats could negatively
affect the North American wolverine's population resilience,
distribution, and gene flow in the future.
Disturbance Due to Winter Recreational Activity: In our 2018 SSA
and October 13, 2020, withdrawal document (85 FR 64618), we concluded
that the effect of winter recreational activity represents a low
stressor to wolverines in the contiguous United States at the
individual and population levels. New information on winter recreation
impacts on North American wolverines is presented below and adds
significantly to our understanding of this factor as highly relevant to
the DPS.
The response of North American wolverines to various levels of
backcountry winter recreation (motorized and nonmotorized) was recently
studied in four areas in Idaho, Montana, and Wyoming (Heinemeyer et al.
2019a, p. 8). The study found that wolverines temporarily avoided areas
within their home range where winter recreation (motorized and
nonmotorized) was occurring (Heinemeyer et al. 2019a, p. 16).
Wolverines increasingly avoided these areas as the amount of off-road
winter recreation increased, resulting in indirect habitat loss or
functional degradation of moderate- or high-quality habitats in winter
(Heinemeye
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