Proposed Rule2023-20946
Endangered and Threatened Wildlife and Plants; Reclassifying the Virgin Islands Tree Boa From Endangered to Threatened With a Section 4(d) Rule
Primary source
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Published
September 27, 2023
Issuing agencies
Interior DepartmentFish and Wildlife Service
Abstract
We, the U.S. Fish and Wildlife Service (Service), withdraw the proposed rule to reclassify the Virgin Islands tree boa (listed as Epicrates monensis granti) from endangered to threatened under the Endangered Species Act of 1973 (Act), as amended. This withdrawal is based on new information we received during the proposed rule's public comment periods, specifically new survey results that indicate that the Virgin Islands tree boa is likely extirpated from Cayo Ratones. We also realized an error in calculations that reduced the resiliency of the Cayo Diablo population. After evaluating the status of the species following these changes, we find that the species still meets the Act's definition of an endangered species. We have, therefore, determined that reclassification of this species is not appropriate at this time. Accordingly, we also withdraw the proposed 4(d) rule for the Virgin Islands tree boa.
Full Text
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[Federal Register Volume 88, Number 186 (Wednesday, September 27, 2023)]
[Proposed Rules]
[Pages 66351-66360]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2023-20946]
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DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
[Docket No. FWS-R4-ES-2019-0069; FF09E21000 FXES11110900000 234]
RIN 1018-BE14
Endangered and Threatened Wildlife and Plants; Reclassifying the
Virgin Islands Tree Boa From Endangered to Threatened With a Section
4(d) Rule
AGENCY: Fish and Wildlife Service, Interior.
ACTION: Proposed rule; withdrawal.
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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), withdraw the
proposed rule to reclassify the Virgin Islands tree boa (listed as
Epicrates monensis granti) from endangered to threatened under the
Endangered Species Act of 1973 (Act), as amended. This withdrawal is
based on new information we received during the proposed rule's public
comment periods, specifically new survey results that indicate that the
Virgin Islands tree boa is likely extirpated from Cayo Ratones. We also
realized an error in calculations that reduced the resiliency of the
Cayo Diablo population. After evaluating the status of the species
following these changes, we find that the species still meets the Act's
definition of an endangered species. We have, therefore, determined
that reclassification of this species is not appropriate at this time.
Accordingly, we also withdraw the proposed 4(d) rule for the Virgin
Islands tree boa.
DATES: The proposed rule that published on September 30, 2020 (85 FR
61700), to reclassify the Virgin Islands tree boa as threatened with a
rule issued under section 4(d) of the Act is withdrawn on September 27,
2023.
ADDRESSES: This withdrawal, comments on our September 30, 2020,
proposed rule, and supplementary documents are available for public
inspection on the internet at <a href="https://www.regulations.gov">https://www.regulations.gov</a> at Docket No.
FWS-R4-ES-2019-0069 and on the Service's website at <a href="https://www.fws.gov/office/caribbean-ecological-services/library">https://www.fws.gov/office/caribbean-ecological-services/library</a>.
FOR FURTHER INFORMATION CONTACT: Edwin E. Mu[ntilde]iz, Field
Supervisor, U.S. Fish and Wildlife Service, Caribbean Ecological
Services Field Office, P.O. Box 491, Boquer[oacute]n, PR 00622;
telephone 787-405-3641; email: <a href="/cdn-cgi/l/email-protection#4f0c2e3d262d2d2a2e21102a3c0f29383c61282039"><span class="__cf_email__" data-cfemail="1c5f7d6e757e7e797d7243796f5c7a6b6f327b736a">[email protected]</span></a>. Individuals in the
United States who are deaf, deafblind, hard of hearing, or have a
speech disability may dial 711 (TTY,
[[Page 66352]]
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:
Previous Federal Actions
Please refer to the September 30, 2020, proposed rule (85 FR 61700)
to reclassify the Virgin Islands tree boa (which we refer to below as
``Virgin Islands boa'') for a detailed description of previous Federal
actions concerning this species. The September 30, 2020, proposed rule
opened a 60-day public comment period, ending November 30, 2020. We
then reopened the public comment period for an additional 30 days, from
April 26 to May 26, 2021, and held a public hearing on May 12, 2021
(see 86 FR 22005; April 26, 2021). During both comment periods and at
the public hearing, we accepted submission of new information and
comments on the proposed reclassification.
Summary of Justification for Withdrawal
Based on the comments we received during both of the September 30,
2020, proposed rule's public comment periods and at the May 12, 2021,
public hearing, we made several changes and corrections throughout the
species status assessment (SSA) report for the Virgin Islands boa
(Service 2022, entire). We received substantive comments regarding the
probable extirpation of Virgin Islands boas due to colonization of rats
on Cayo Ratones, and we have included that information in all
descriptions of that population and addressed it in our analysis.
Results from a survey effort in September 2021 by Puerto Rico
Department of Natural and Environmental Resources (DNER) and other boa
experts were provided to the Service; no boas or indirect evidence of
boas were observed (Puente-Rol[oacute]n et al. 2021, p. 1) and the DNER
affirms that the Cayo Ratones population is most likely extirpated
(DNER 2019, p. 3). We also received comments on the characterization of
the resiliency of the Cayo Diablo population, and upon reexamination of
the current resiliency score, we realized we made an error in our
calculations and subsequently have changed the resiliency of that
population from moderately high resiliency to moderate resiliency. Upon
incorporating these changes, we have determined that there are not
sufficient data to support reclassifying the Virgin Islands boa from an
endangered species to a threatened species. Accordingly, we are
withdrawing our proposed rule to reclassify the Virgin Islands boa as a
threatened species with a rule issued under section 4(d) of the Act (16
U.S.C. 1531 et seq.).
Proposal to Update the Scientific Name of the Virgin Islands Tree Boa
In the September 30, 2020, proposed rule (85 FR 61700), we proposed
to correct the Federal List of Endangered and Threatened Wildlife
(List) to change the scientific name of the Virgin Islands tree boa
from Epicrates monensis granti to Chilabothrus granti to reflect the
currently accepted taxonomy. Virgin Islands boa is a distinct species,
not a subspecies, and Epicrates is no longer the scientifically
accepted genus for this species. However, because we are withdrawing
the September 30, 2020, proposed rule (85 FR 61700), the Virgin Islands
boa's scientific name will remain Epicrates monensis granti in the List
until we, in the future, publish a final rule recognizing the new
taxonomy.
Background
A thorough review of the taxonomy, life history, ecology, and
overall viability of the Virgin Islands boa is presented in the SSA
report (Service 2022, entire; available at <a href="https://www.regulations.gov">https://www.regulations.gov</a>
under Docket No. FWS-R4-ES-2019-0069). A summary of this information
follows.
The Virgin Islands boa is endemic to Puerto Rico and the Virgin
Islands (U.S. and British). The Virgin Islands boa is a medium-length,
slender, nonvenomous snake. The largest snout-vent lengths (SVL)
recorded for the species were 1,066 millimeters (mm; 42 inches (in))
for females and 1,112 mm (44 in) for males (total body lengths 1,203 mm
(47 in) and 1,349 mm (53 in), respectively; Tolson 2005, entire),
although most specimens range between 600 and 800 mm (24 and 31 in)
SVL, with an average mass of 165 grams (6 ounces) (USVI Division of
Wildlife, unpublished data). Adults are gray-brown with dark-brown
blotches that are partially edged with black, and feature a blue-purple
iridescence on their dorsal surface; the ventral surface is creamy
white or yellowish white. Newborns, on the other hand, have an almost
grayish-white body color with black blotches and weigh 2.0-7.2 grams
(0.07-0.25 ounces) with SVLs of 200-350 mm (approx. 8-14 in) (Tolson
1992, entire; Tolson 2018, pers. comm.).
The Virgin Islands boa occurs in subtropical dry forest and
subtropical moist forest (Service 2009, p. 11). Subtropical dry forest
covers approximately 14 percent (128,420 hectares (ha); 317,332 acres
(ac)) of Puerto Rico and the U.S. Virgin Islands (USVI), typically
receives less than 750 mm (29 in) rainfall annually (Ewel and Whitmore
1973, pp. 9-20), and is characterized by small (less than 5 meter (m;
16 feet (ft)) deciduous trees with high densities of interlocking
branches and vines connecting adjacent tree canopies (Ewel and Whitmore
1973, p. 10). Subtropical moist forest covers approximately 58 percent
(538,130 ha; 1,329,750 ac) of Puerto Rico and USVI and typically
receives more than 1,100 mm (43 in) of annual rainfall. It is dominated
by semi-evergreen and evergreen deciduous trees up to 20 m (66 ft) tall
with rounded crowns. The Virgin Islands boa has also been reported to
occur in mangrove forest, thicket/scrub, disturbed lower vegetation,
and artificial structures (Harvey and Platenberg 2009, p. 114; Tolson
2003, entire).
Habitat needs for Virgin Islands boa can be divided into those for
foraging and those for resting. Factors contributing to foraging
habitat quality are tree density and connectivity, presence of arboreal
and ground-level refugia, prey density, and rat presence/density
(Tolson 1988, pp. 234-235). Tree density is more important than tree
species or diversity; Virgin Islands boas do not appear to prefer a
particular tree species after accounting for availability and structure
(Platenberg 2006, pers. comm.). The highest densities of Virgin Islands
boas are found where there are few or no exotic predators and high
densities of lizard prey (Tolson 1988, p. 233). Resting habitat
includes refugia for inactive boas to use during the day. Refugia can
be the axils (angles between trunk and branches) of Cocos or Sabal
species, tree holes, termite nests, or under rocks and debris (Tolson
1988, p. 233).
The Virgin Islands boa forages at night by gliding slowly along
small branches in search of sleeping lizards (Service 1986, p. 6). The
primary prey for the Virgin Islands boa is the Puerto Rican crested
anole (Anolis cristatellus), and the greatest concentrations of Virgin
Islands boa are found where Anolis densities exceed 60 individuals/100
m\2\ (1,076 ft\2\; Tolson 1988, p. 233). Other prey species include
ground lizard (Ameiva exsul), house mouse (Mus musculus), small birds,
iguana (Iguana iguana) hatchlings, and likely other small animals
encountered (MacLean 1982, pp. 30-31, 37; Tolson 1989, p. 165; Tolson
2005, p. 9; Platenberg 2011, p. 3). The Virgin Islands boa may also
compete for prey and other niche components with the green iguana
(Iguana iguana) and the Puerto Rican
[[Page 66353]]
racer (Borikenophis portoricensis), a snake native to Puerto Rico,
USVI, the British Virgin Islands, and surrounding cays (small, low
islands).
Much of what is known about the Virgin Islands boa's life history
comes from studies in captivity. Lifespans in captivity often exceed 20
years, and sometimes exceed 30 years (7 percent of captive Virgin
Islands boas exceeded 30 years of age; Smith 2018c, pers. comm.), but
typical lifespans in the wild are not known. Sexual maturity is reached
at 2 to 3 years of age (Tolson 1989, pp. 165-166; Tolson and
Pi[ntilde]ero 1985, pp. 5-6), and boas are still reproductive at up to
20 years of age (Tolson 2018, pers. comm.). Females breed biennially,
but studies have suggested that annual breeding may occur in some
conditions (Tolson and Pi[ntilde]ero 1985, pp. 6-7). Courtship
behaviors and copulation occur from February through May, and
interaction with conspecifics of the opposite sex appears to be
necessary for reproductive cycling (Tolson 1989, p. 165). The gestation
period, observed from a single known copulation between two
individuals, is about 132 days (Tolson 1989, p. 165). Virgin Islands
boas give birth to live young from late August through October to
litters of 2 to 10 young, and litter size increases with female body
size (Tolson 2018, pers. comm.).
The exact historical distribution of the Virgin Islands boa is
unknown, but its present disjointed distribution suggests that it was
once more widely distributed across small islands within its range. In
the 1970s, when the Virgin Islands boa was listed under the Endangered
Species Conservation Act of 1969, its range was identified as three
islands: Puerto Rico (no specific site); St. Thomas, USVI (from a
single record); and Tortola in the British Virgin Islands (BVI) (from
one report) (44 FR 70677; December 7, 1979). When the recovery plan was
written (1986), 71 individuals were reported in two populations: one on
the eastern side of St. Thomas in the USVI, and one at Cayo Diablo, an
offshore islet in Puerto Rico (Service 2009, p. 6).
Currently, the Virgin Islands boa occurs on six islands between
Puerto Rico, USVI, and BVI: the eastern Puerto Rican islands of Cayo
Diablo and Culebra; R[iacute]o Grande on the Puerto Rican main island;
eastern St. Thomas and an offshore cay in USVI (USVI Cay; an introduced
population); and Tortola. The occurrence of a seventh population (also
an introduced population) on the Puerto Rican cay of Cayo Ratones is
considered uncertain after the reestablishment of rats on this island
possibly sometime after 2004 (Service 2022, p. 24). Surveys in April
2018 and September 2021 did not find Virgin Islands boas on Cayo
Ratones (Island Conservation 2018, pp. 5, 17; DNER 2021, unpublished
data; Puente-Rol[oacute]n et al. 2021, entire), indicating this
population is likely extirpated. Lastly, there is also one report from
2004 that the species occurs on Greater St. James Island in St. Thomas,
but nothing is known about that potential population (Dempsey 2019,
pers. comm.). In 2009, based on all known populations in Puerto Rico
and the USVI, an estimated 1,300-1,500 Virgin Islands boas were thought
to occur (Service 2009, p. 8). However, some population numbers used
for that estimate are speculative. The current overall estimate of the
species is unknown, particularly with the likely extirpation of the
Cayo Ratones population. Based on the 2022 SSA report (Service 2022,
entire), current population trend estimates for Puerto Rico and USVI
are either declining, potentially declining, considered rare, or
unknown, and most populations are small or considered rare (Service
2022, p. 30).
The population on Tortola Island, BVI, was confirmed in 2018, but
there are no specific data regarding the status of that population
(McGowan 2018, pers. comm.). In addition, according to anecdotal
reports, the species is thought to occur on Jost Van Dyke, Guana
Island, Necker Cay, Great Camanoe, and Virgin Gorda of the BVI (Mayer
and Lazell 1988, entire), but data and confirmed observations are
limited. There is not enough information to reliably assess the status
of Virgin Islands boa populations on those islands, and they are not
included in our analysis.
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
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
[[Page 66354]]
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 Act's 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 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 SSA report (Service 2022, entire) documents the results of our
comprehensive biological review of the best scientific and commercial
data regarding the status of the species, including an assessment of
the potential threats to the species. The SSA report does not represent
a decision by the Service on whether the species should be listed as an
endangered or threatened species under the Act. It does, however,
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. The following is a summary
of the key results and conclusions from the SSA report; the full SSA
report can be found at Docket FWS-R4-ES-2019-0069 on <a href="https://www.regulations.gov">https://www.regulations.gov</a>.
To assess Virgin Islands boa's viability, we used the three
conservation biology principles of resiliency, redundancy, and
representation (Shaffer and Stein 2000, pp. 306-310). Briefly,
resiliency supports the ability of the species to withstand
environmental and demographic stochasticity (for example, wet or dry,
warm or cold years), redundancy supports 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, pathogens). 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 species' ecological requirements for
survival and reproduction at the individual, population, and species
levels, and described the beneficial and risk factors influencing the
species' viability.
The SSA process can be categorized into three sequential stages.
During the first stage, we evaluated the individual species' life-
history needs. The next stage involved an assessment of the historical
and current condition of the species' 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 species' 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 to sustain populations in the
wild over time. We use this information to inform our regulatory
decision. Our SSA was revised to reflect the comments and new
information we received during both of the September 30, 2020, proposed
rule's public comment periods and at the May 12, 2021, public hearing.
Summary of Biological Status and Threats
In this discussion, we review the biological condition of the
species and its resources, and the threats that influence the species'
current and future condition, in order to assess the species' overall
viability and the risks to that viability. In the SSA report (Service
2022, pp. 12-18), we reviewed all factors (i.e., threats, stressors)
that could be affecting the Virgin Islands boa now or in the future.
However, in this document, we will focus our discussion only on those
factors that could meaningfully impact the status of the species. The
risk factors affecting the status of the Virgin Islands boa vary from
location to location, but generally include habitat loss and
degradation from development, introduced predators, sea level rise
(SLR) and a changing climate, and public attitudes towards snakes.
Where habitat is available but the species is not present (i.e., most
of the small islands in the eastern Puerto Rico bank and USVI), it is
believed that absences are due to local extirpation resulting from
habitat degradation and colonization of exotic species (Service 2009,
p. 11). We discuss each of the risk factors below.
Habitat Loss and Degradation--Development
Virgin Islands boas occur on both privately and publicly owned
land. Virgin Islands boas have been observed living in developed areas
around residences and can persist within developed areas if habitat
patches are available, but only if no cats or rats are around
(Platenberg and Harvey 2010, p. 552; Platenberg 2011, p. 11).
Development continues to impact populations via habitat destruction,
especially in St. Thomas, R[iacute]o Grande (Puerto Rico), and Culebra
Island where habitat has declined over decades. In St. Thomas,
available habitat has declined due to development for resorts, condos,
and related infrastructure, and habitat has become more constricted and
isolated (Platenberg and Harvey 2010, p. 552). In Puerto Rico, human
populations are decreasing, but residential development continues to
increase island-wide, including around protected areas (Castro-Prieto
et al. 2017, entire). Consequences of human development on the boa and
its habitat not only include habitat loss and fragmentation due to
deforestation, but also mortality from vehicular strikes, an increase
in predators such as cats and rats, and an increase in human-boa
conflicts that results in snakes being killed because of fear of snakes
(Service 2022, pp. 13-14).
Predation and Competition
One of the primary threats to Virgin Islands boa populations is
predation by exotic mammalian predators, mainly cats and rats, and
possibly, to a lesser degree, mongoose. Mongoose are not likely a major
predator of Virgin Islands boa because mongoose are terrestrial and
active during the day, while Virgin
[[Page 66355]]
Islands boas are arboreal and active primarily at night, although not
exclusively (Service 2022, p. 14). Feral cats are known to prey upon
boas (Tolson 1996b, p. 409), and cat populations around human
development are further bolstered by cat feeding stations set up by
residents. There has not been direct evidence of rats preying upon
Virgin Islands boas, but boas are not present on islands with high
densities of rats (Tolson 1986ab, unpaginated; Tolson 1988, p. 235).
Rats likely negatively impact Virgin Islands boas by competing for
prey, or by inducing behavioral changes in Anolis prey that make them
less likely to be encountered by boas (Tolson 1988, p. 235). However,
rats may also predate on neonate boas (Service 1986, p. 12). Complete
predator removal on large, developed islands is challenging, but is
feasible on smaller cays. Prior to reintroduction of the boas, rats
were eliminated from Cayo Ratones and the USVI Cay using anticoagulant
poison (Tolson 1996b, p. 410), although Cayo Ratones was recolonized by
rats sometime after August 2004, highlighting the importance of ongoing
monitoring for rat presence after a removal project. Cayo Ratones was
thought to harbor one of the most robust Virgin Islands boa
populations, but during the April 2018 survey (Island Conservation
2018, p. 20) and more recent September 2021 survey (DNER 2021,
unpublished data; Puente-Rol[oacute]n et al. 2021, entire), no boas
were found.
Effects of Climate Change, Including Sea Level Rise
Climate change will continue to influence the Virgin Islands boa's
viability into the future. Species such as the Virgin Islands boa, that
are dependent on specialized habitat types or limited in distribution,
are the most susceptible to the impacts of climate change (Byers and
Norris 2011, p. 22).
The climate in the southeastern United States and Caribbean has
warmed about 2 degrees Fahrenheit ([deg]F) from a cool period in the
1960s and 1970s, and temperatures are expected to continue to rise
(Carter et al. 2014, pp. 398-399). Projections for future precipitation
trends in this area are less certain than those for temperature, but
they suggest that overall annual precipitation will decrease and
tropical storms will occur less frequently but with more force (i.e.,
more category 4 and 5 hurricanes) than historical averages (Carter et
al. 2014, pp. 398-399; Knutson et al. 2010, pp. 161-162). With
increasing temperatures and decreasing precipitation, drought could
negatively influence Virgin Islands boa populations. After a severe
drought in eastern Puerto Rico, Anolis populations crashed on Cayo
Diablo, and body condition indices of the boas plummeted (Tolson 2018,
pers. comm.).
Sea levels are expected to rise globally, ranging from 0.2 m (7.9
in) to over 1 m (3 ft) of SLR by the end of the century (Reynolds et
al. 2012, p. 3; Service 2022, p. 38). Local SLR impacts in the
Caribbean will depend on how much the ocean level itself rises, and on
land subsidence or changes in offshore currents, but are predicted to
range from 0.17 m (6.7 in) to 0.38 m (15.0 in) by 2065 (Carter et al.
2014, p. 400; Service 2022, p. 38). Impacts on terrestrial ecosystems
can be temporary, via submergence of habitat during storm surges, or
permanent, via saltwater intrusion into the water table, inundation of
habitat, and erosion. SLR and hurricane storm surges in the Caribbean
are predicted to inundate low-lying islands and parts of larger islands
(Bellard et al. 2014, pp. 203-204). The low-lying islands of Cayo
Diablo and the USVI Cay, which support Virgin Islands boa populations,
and the island of Cayo Ratones, where we are uncertain if the island
still supports a population, are all vulnerable to SLR and storm surges
in the future. Boa populations on R[iacute]o Grande, Culebra, and St.
Thomas are not considered at risk from SLR; however, the three cays
(Cayo Diablo, Cayo Ratones, and USVI Cay) could see 10-23 percent loss
of low-lying habitat due to SLR over the next 30 years (Service 2022,
pp. 38-46). Past and current observations suggest that the species can
survive major hurricane events, although lasting impacts to habitat,
particularly die-off of vegetation inundated by storm surges, have been
observed (Platenberg 2018, pers. comm.; Smith 2018c, pers. comm.;
Tolson 1991, pp. 12, 16; Yrigoyen 2018, pers. comm.). Loss of habitat
due to storm surge impacts is similar to loss of habitat due to
development; loss of low-lying forest habitat could result in decreased
habitat availability for the Virgin Islands boas and their prey.
Persecution by Residents
Intentional killing of the more common and larger sized Puerto
Rican boa (Chilabothrus inornatus) due to fear or superstitious beliefs
has been well documented (Bird-Pic[oacute] 1994, p. 35; Puente-
Rol[oacute]n and Bird-Pic[oacute] 2004, p. 343; Joglar 2005, p. 146).
Thus, Virgin Islands boas in proximity to developed areas where people
fear snakes are susceptible to intentional killings. Public encounters
with Virgin Islands boas in the more populated R[iacute]o Grande and
Culebra locations are considered questionable because of the rarity of
boas in those populations, and there are only a couple of anecdotal
records of intentional killings in those areas (Service 2009, pp. 15-
16). In the highly developed east side of St. Thomas, about 10 percent
of the Virgin Islands boa records in St. Thomas are from boas killed by
humans on private property (Platenberg 2006, unpublished data). We have
no further information to assess the magnitude of this threat, but it
is likely that intentional killings of Virgin Islands boas still occur,
are not being documented, and would be particularly detrimental to rare
populations such as in R[iacute]o Grande. The Service is not aware of a
law enforcement case related to the boa in Puerto Rico or the USVI.
Populations that occur within protected areas are not expected to be
exposed to this threat.
Conservation Measures and Regulatory Mechanisms That Affect the Species
Positive influences on the Virgin Islands boa's viability have been
habitat protection, predator control, and captive breeding and
reintroduction. Two populations of Virgin Islands boa were reintroduced
to protected cays after predators had been removed, one on Cayo Ratones
(Puerto Rico) in 1993, and another on USVI Cay in 2002. Founders for
these reintroductions came largely from a cooperative captive-breeding
program initiated in 1985 between the Service, Puerto Rico DNER, U.S.
Virgin Islands Department of Planning and Natural Resources (VIDPNR),
and Toledo Zoological Garden. Cayo Diablo provided the founding
individuals for the captive population that was reintroduced to Cayo
Ratones (6 kilometers (3.5 miles) away from Cayo Diablo), and St.
Thomas provided the founding individuals for the captive population
that was reintroduced to the USVI Cay (4 kilometers (2.5 miles) away
from St. Thomas).
The Cayo Ratones population originated from 41 captive-born boas
(offspring of Cayo Diablo boas) released between 1993 and 1995. Post-
release survival was high: 82.6 percent of individuals and 89 percent
of neonates survived at least 1 year (Tolson 1996a, unpaginated). By
2004, the population had grown to an estimated 500 boas (Tolson et al.
2008, p. 68). Unfortunately, since 2004, Cayo Ratones has been
recolonized by rats, and no boas were found during surveys in April
2018 (Island Conservation 2018, pp. 5, 20) and September 2021 (DNER
2021, unpublished data; Puente-Rol[oacute]n et al. 2021, entire).
However, because Virgin Islands boas are difficult to find,
[[Page 66356]]
additional surveys are needed to confirm whether a few individuals
still persist or to conclude that the population is extirpated.
The USVI Cay reintroduction was initiated with the release of 42
Virgin Islands boas in 2002 and 2003, 11 from captivity and 31 from St.
Thomas. Follow-up surveys in 2003-2004 provided an estimate of 168 boas
(202 boas per hectare), which researchers suspected was near carrying
capacity for the island (Tolson 2005, p. 9). More recent surveys in
March 2018 detected 20 boas over 2 nights and 44 boas over 3 nights in
November and December 2018 (Smith 2018ab, entire). These recent surveys
revealed a potential decline in abundance and the loss of two prey
species (Smith 2018ab, entire), possibly as a result of density
dependence as the population approached carrying capacity after
reintroduction. Differences in survey and analysis methodologies
complicate direct comparisons of population size between the surveys.
Recent surveys also indicate that there are no rats on the island.
Additional surveys are being conducted by the VIDPNR that will help
continue to monitor this population and refine current estimates.
Factors for consideration for future reintroduction sites include the
presence and amount of suitable habitat (e.g., appropriate forest
structure, adequate prey base, available refugia), protection status or
threat of development, the presence/absence/eradication of exotic
predators, and geomorphology that provides protection from SLR and
hurricane storm surges that are likely to affect the persistence of
low-lying habitat. Potential sites for new introductions have been
suggested (Reynolds et al. 2015, p. 499) and need to be further
assessed, with one offshore island in St. Thomas as one of the primary
sites. Some areas may require that predators be removed before boas are
reintroduced and future monitoring is ensured to prevent recolonization
by predators. In addition to reintroductions to new sites, augmentation
of existing populations may prove beneficial or necessary for the
persistence of existing populations, particularly on developed islands
and cays where predators have become reestablished.
Both Puerto Rico and the USVI have regulatory mechanisms
established to protect the species and its habitat through consultation
processes for the authorization of development projects. Presently, the
Virgin Islands boa is legally protected under Puerto Rico's
Commonwealth Law No. 241-1999 (see title 12 of the Laws of Puerto Rico
at section 107 et seq. (12 L.P.R.A. sec. 107 et seq.)), known as Nueva
Ley de Vida Silvestre de Puerto Rico (New Wildlife Law of Puerto Rico).
This law has provisions to protect habitat for all wildlife species,
including plants and animals. In addition, the species is protected by
Puerto Rico DNER's Regulation 6766 (Reglamento para Regir el Manejo de
las Especies Vulnerables y en Peligro de Extincio[acute]n en el Estado
Libre Asociado de Puerto Rico (Regulation 6766: To govern the
management of threatened and endangered species in the Commonwealth of
Puerto Rico)). Article 2.06 of Regulation 6766 prohibits collecting,
cutting, and removing, among other activities, listed plant and animal
individuals within the jurisdiction of Puerto Rico (DRNA 2004, entire).
In the USVI, Act No. 5665, known as the Virgin Islands' Indigenous and
Endangered Species Act, which is enforced by the VIDPNR, protects the
species.
Despite these regulations being in place, including the requirement
for developers to conduct environmental assessments and mitigate damage
to the species and habitat, the regulations have proved difficult to
enforce, they are often ignored by developers, and they do not cover
all development activities in all Virgin Islands boa habitat
(Platenberg 2011, pp. 11-13). For example, in St. Thomas, major permit
applications submitted for projects in the coastal zone require an
environmental impact assessment that addresses endangered species and
protected habitat, but these requirements do not apply to smaller
projects or those outside of the coastal zone. Furthermore, as noted in
one study, even though a protocol was developed and applied to
delineate habitat on protected sites and identify mitigation
strategies, the absence of a legal mechanism to enforce mitigation has
led to varying success as developers are slow to accept, and often
ignore, the mitigation process (Platenberg and Harvey 2010, pp. 551-
552).
Most offshore cays within the species' range are part of the
Territorial Government or protected as wildlife refuges, thus formally
protecting Virgin Islands boa habitat for three of the six populations
(i.e., Cayo Diablo, Cayo Ratones, and USVI Cay). Cayo Ratones and Cayo
Diablo are included in La Cordillera Natural Reserve managed by the
Puerto Rico DNER, and the offshore cay in USVI is managed and protected
by the VIDPNR. Furthermore, even though Virgin Islands boa habitat on
privately owned land on Culebra Island is currently under pressure from
urban and tourism development and deforestation, more than 1,000 acres
of suitable habitat on the island are protected within the Service's
Culebra National Wildlife Refuge.
In conclusion, the Virgin Islands boa still faces the threat of
development on St. Thomas, R[iacute]o Grande, and Culebra Island, and
regulatory mechanisms addressing this threat are difficult to enforce
or do not cover all development actions affecting the species. Human
development results in habitat loss from deforestation and
fragmentation, mortality from vehicular strikes, and increased
predation by cats and rats. In addition, impacts from changes in
climate could affect habitat. Drought could negatively influence Virgin
Islands boa populations through loss of prey. SLR and storm surges are
expected to inundate low-lying islands, such as Cayo Diablo, Cayo
Ratones, and the USVI Cay, which currently support Virgin Islands boa
populations. Finally, persecution of boas by citizens, due to fear or
superstition, can affect individual boas, although there has never been
a systematic study of the impact of these events on the overall
population.
When considering conservation actions and how they influence the
viability of Virgin Islands boa, about half of known localities where
Virgin Islands boas occur are on small offshore islets managed for
conservation. In addition, predator removal has been successful at
smaller cays, such as USVI Cay, although the reestablishment of rats on
Cayo Ratones illustrates the need for continued monitoring and removal
efforts. Lastly, successful reintroductions of Virgin Islands boas
occurred on these islands after the eradication of predators.
Current Condition
For the Virgin Islands boa to maintain viability, its populations,
or some portion thereof, must be resilient. For the SSA report (Service
2022, entire), our classification of resiliency relied heavily on
habitat characteristics in the absence of a certain population size for
most populations or trend estimates. The habitat characteristics we
assessed were degree of habitat protection (or, conversely, development
risk), presence of introduced predators, and vulnerability to storm
surges (Service 2022, p. 31).
Representation can be measured by the breadth of genetic or
environmental diversity within and among populations and gauges the
probability that a species is capable of adapting to environmental
changes. A rangewide genetic analysis of the Virgin Islands boa showed
there was little genetic variation; however, the
[[Page 66357]]
same study found that each sampled locality had unique mtDNA
haplotypes, indicating a lack of gene flow between islands
(Rodr[iacute]guez-Robles et al. 2015, entire). Therefore, in the SSA
report we used genetics to delineate representative units.
The species also needs to exhibit some degree of redundancy in
order to maintain viability. Catastrophic events that could affect both
single and multiple populations of the Virgin Islands boa include
drought, hurricanes, and colonization or recolonization of exotic
predators. This species occurs in geographically isolated groups and
does not disperse from island to island to interact and interbreed;
therefore, for purposes of analyzing redundancy, all boas within each
island were considered to be individual populations.
Resiliency
Because resiliency is a population-level attribute, the key to
assessing it is the ability to delineate populations. As discussed
above, we considered all boas within each island to be single
populations. On small offshore cays, what we define as a population
might consist of a single interbreeding deme (or subdivision) of Virgin
Islands boas. On larger islands, what we define as a population
functions more as a metapopulation, with multiple interbreeding groups
in isolated habitat patches that may interact weakly via dispersal and
recolonization of extirpated patches. Alternately, multiple occupied
patches on large islands may be completely isolated from one another
(Service 2022, p. 20).
Six island populations were considered: Cayo Diablo, Cayo Ratones,
Culebra Island, R[iacute]o Grande (Puerto Rico), St. Thomas, and USVI
Cay (USVI). Further, one or more populations exist in the BVI (e.g.,
Tortola), but data are severely limited, and for the SSA report, we
lacked sufficient data from these islands to incorporate them into our
viability analysis. In addition, other populations may occur on other
offshore islands in Puerto Rico and USVI, but most have not been
searched for Virgin Islands boas and we could not confirm any to be
extant at the time we completed our analysis.
Resiliency scores for each population were generated by combining
scores for three habitat metrics ((1) protection/development risk, (2)
exotic mammals, and (3) storm surge risk) and one population metric
(population size and/or trend, dependent on availability). Each metric
was weighted equally, with the overall effect that habitat (three
metrics) was weighted three times higher than population size/trend
(one metric). For each metric, populations were assigned a score of -1,
0, or 1, as described below in table 1.
The scores were based on the best available information for each
population, gathered from the literature and species experts.
Monitoring data are scarce. The Virgin Islands boa recovery plan
(Service 1986, pp. 16-19) called for periodic monitoring to estimate
population sizes and trends, but surveys since then have been few and
far between. Survey methodology and reporting have varied from
population to population, with survey results given as estimated
abundances, estimated densities, or encounter rates per person-hour of
searching. The above-described factors in combination contribute to
high levels of uncertainty in current and past population sizes, and
how they have changed over time. Accordingly, resiliency
classifications relied more heavily on habitat conditions than
population size and trend estimates.
Table 1--Description of Habitat and Population Factor Scores To Determine the Virgin Islands Boa's Population
Resiliency
----------------------------------------------------------------------------------------------------------------
Habitat metrics Population metric
---------------------------------------------------------------------------------------
Score Habitat protection/ Population Size/
development risk Exotic mammals Storm surge risk Trend *
----------------------------------------------------------------------------------------------------------------
-1...................... Habitat not Exotic mammals Topography and Relatively low
protected, at risk present. elevation leaves population size and/
of being developed. population or declining trend.
vulnerable to storm
surges.
0....................... Some habitat Not applicable (not Not applicable (not <bullet> Relatively
protected, some at present). an issue). moderate population
risk of being size and stable
developed. trend, or
<bullet> High degree
of uncertainty in
population size/
trends.
1....................... Habitat protected in Exotic mammals Protected by Relatively high
identified absent. topography and population size and/
protected area. elevation. or growth.
----------------------------------------------------------------------------------------------------------------
* Population size/trend scores are relative and were based on the best available information for each
population, gathered from the literature and species experts.
The scores for each population across all metrics were summed, and
final population resiliency categories were assigned as follows:
Low Resiliency: -4 to -2
Moderately Low Resiliency: -1
Moderate Resiliency: 0
Moderately High Resiliency: 1
High Resiliency: 2 to 4
Applying these resiliency categories to the six populations of
Virgin Islands boa, we determined that two populations have moderate
resiliency (Cayo Diablo and USVI Cay), one has moderately low
resiliency (Culebra), two have low resiliency (R[iacute]o Grande and
St. Thomas), and one has no resiliency because it is presumed to be
extirpated (Cayo Ratones).
One of the populations classified as having moderate resiliency
(Cayo Diablo) occurs on a small offshore island that is free of exotic
rats and cats and is protected for conservation. Boas have been
consistently found on Cayo Diablo, with an April 2018 survey detecting
10 boas (Island Conservation 2018, entire), one in November 2018 that
detected 14 boas (DNER 2018, unpublished data), and one in April 2022
that detected 2 boas (Smith 2022, unpublished data). Using the April
2018 data, extrapolating the density within the transect area (2.9 boas
per hectare) to the entire island, the model provides an estimate of 20
boas on the island (95 percent confidence interval 13-39). This number
is lower than earlier unpublished survey results; however, direct
comparisons cannot be made with past surveys because of different
survey and analytical methodologies (Service 2022, p. 23). The previous
efforts in 1993 had marked over 250 snakes in Cayo Diablo (Tolson
1996b, p. 411),
[[Page 66358]]
with an estimate of approximately 500 boas in the cay. Because of the
protected and exotic-mammal-free state of the habitat, but with
potentially declining numbers, this Cayo Diablo population is
considered to have moderate resiliency to demographic and environmental
stochastic events and disturbances (e.g., fluctuations in demographic
rates, variation in climatic conditions, illegal human activities).
The USVI Cay population, also on a protected offshore island with
no exotic mammals, was also determined to have moderate resiliency.
Previous survey efforts from 2004 resulted in a population estimate of
168 snakes (Tolson 2005, p. 9). Recent surveys have revealed a
potential decline in abundance and the loss of two prey species (Smith
2018ab, entire), possibly as a result of density dependence as the
population approached carrying capacity after reintroduction. Over two
separate survey efforts in 2018, researchers found a total of 64 boas,
including 10 recaptures (Smith 2018ab, entire). Additional surveys are
being conducted by the VIDPNR, and although we do not have the results,
additional boas have been detected (VIDPNR 2022, unpublished data).
The Culebra population, with some portions of habitat protected as
part of Culebra National Wildlife Refuge, was determined to have
moderately low resiliency. Surveys in 2018 found no boas (Island
Conservation 2018, p. 20); however, two individuals were documented in
February 2019 within the Culebra National Wildlife Refuge (Puente-
Rol[oacute]n and Vega-Castillo 2019, p. 18). In October 2019, another
individual was confirmed in an area outside of the refuge (Rom[aacute]n
2019, pers. comm.).
Three of the populations (R[iacute]o Grande, Culebra, and St.
Thomas) with moderately low or low resiliency occur on larger and
higher elevation islands, which provide more protection from storm
surges, but have more human-boa interactions, habitat loss and
fragmentation from development, and exotic cats and rats. Recent
surveys in 2018 on R[iacute]o Grande found three boas (three survey
nights) (Island Conservation 2018, p. 20). For St. Thomas, there have
been no recent systematic surveys for the species as much of eastern
St. Thomas is inaccessible due to private ownership or impenetrable
habitat. Previous uncertain conservative estimates for this population
ranged from 300 to 400 individuals (Tolson 1991, p. 12) to fewer than
100 individuals based on effective population size estimates (Reynolds
et al. 2015, p. 498).
The remaining Cayo Ratones population is classified as not having
resiliency because of the recolonization of rats on the island and
subsequent declining trend of boas, which we presume to be extirpated,
as no boas were detected during recent survey efforts conducted in
April 2018 and September 2021.
Representation
A rangewide genetic analysis of Virgin Islands boa showed that
there was little genetic variation within the species
(Rodr[iacute]guez-Robles et al. 2015, p. 150), supporting the idea that
there is only one representative unit of Virgin Islands boa. However,
each sampled island, and each sampled locality within the same island,
had unique mtDNA haplotypes, indicating a lack of gene flow between
islands/populations (Rodr[iacute]guez-Robles et al. 2015, p. 150).
These results suggest that each population has a different genetic
signature, perhaps as a result of genetic adaptations to their local
environment, or genetic drift with increasing isolation of small
populations. The reintroduction program took this view, and managed
captive populations sourced from Cayo Diablo and St. Thomas separately
(Tolson 1996b, p. 412). To minimize the chances of introducing
individuals poorly suited to their new environment, the captive
population sourced from Cayo Diablo founded the reintroduced population
on nearby Cayo Ratones, and the captive St. Thomas population founded
the reintroduced population on the nearby USVI Cay (Tolson 1996b, p.
412).
In addition to genetic differences, the six populations also have
noticeable phenotypic differences. These are not just limited to
coloration differences between USVI and Puerto Rican populations
(Tolson 1996b, p. 412); Cayo Diablo reportedly has lighter coloration
than the R[iacute]o Grande and Culebra populations (Tolson 2018, pers.
comm.). The R[iacute]o Grande population also occurs in a different
habitat type (subtropical moist forest) than the others (subtropical
dry or littoral forest; Tolson 1996b, p. 410).
In light of this information, we considered each of the four
natural populations in Puerto Rico and USVI as a representative unit
(see table 2, below). The Cayo Diablo population is considered to have
moderate resiliency. As this was the source for the now presumed
extirpated Cayo Ratones population, there is only one population
representing the Cayo Diablo genetic signature. The USVI Cay population
was sourced from St. Thomas, so there are two populations with St.
Thomas representation, with neither considered to have high resiliency.
The other two natural populations, Culebra and R[iacute]o Grande, both
characterized as having moderately low or low resiliency, have not been
used for captive breeding and reintroduction, and so have no additional
populations on other islands with the same genetic characteristics.
Overall, two of four representative units have at least one moderately
resilient population.
Table 2--Representation: Number of Virgin Islands Boa Populations of Each Resiliency Class in Each
Representative Unit, Corresponding to Natural (Not Introduced) Populations, Which Themselves Correspond to
Unique Genetic Signatures
----------------------------------------------------------------------------------------------------------------
High or Low or
moderately Moderate moderately
Natural population (genetic signature) high resilience low resilience
resilience populations populations
populations or extirpated
----------------------------------------------------------------------------------------------------------------
Cayo Diablo..................................................... 0 1 1
Culebra......................................................... 0 0 1
R[iacute]o Grande............................................... 0 0 1
St. Thomas...................................................... 0 1 1
----------------------------------------------------------------------------------------------------------------
While currently we could consider the USVI Cay reintroduced
population (currently with moderate resiliency) to be a redundant
population sharing the same genetic signature and adaptive potential as
its source population, all
[[Page 66359]]
islands occupied by Virgin Islands boa are isolated from each other.
Without human-mediated movement of boas between islands, reintroduced
populations are expected to diverge genetically from their source
populations over time, and may at some point in the future (decades to
centuries; Reynolds et al. 2015, entire) be different enough to be
considered their own unique representative unit.
Redundancy
Redundancy describes the ability of a species to withstand
catastrophic events. Measured by the number of populations, their
resiliency (ability of a species to withstand environmental and
demographic stochasticity (e.g., wet or dry years)) and their
distribution (and connectivity), redundancy gauges the probability that
the species has a margin of safety to withstand or return from
catastrophic events (such as a rare destructive natural event or
episode involving many populations).
The exact historical distribution of the Virgin Islands boa is
unknown, but its present disjointed distribution suggests that it was
once more widely distributed across small islands within its range,
which have been subject to local extirpations from habitat degradation,
invasive species, and historical climate and sea level changes.
However, for current redundancy, we identified the five populations in
Puerto Rico and USVI. As discussed above, two of these populations are
considered to have a moderate level of resiliency, which provides some
ability to withstand the effects of catastrophic events. However, these
populations are considered small and potentially declining or trend
unknown. Therefore, overall redundancy for the species is low.
Current Condition Summary
Of the six assessed populations, the Cayo Diablo population and the
USVI Cay population have moderate resiliency and the Culebra population
has moderately low resiliency. The other three assessed populations
currently have low resiliency or are likely extirpated (Cayo Ratones).
Redundancy for the species includes populations on five islands in
Puerto Rico and USVI, and possibly more in the BVI, although islands in
the BVI are not part of this assessment. Representation consists of
four representative units, one of which has two populations
representing its genetic signature, and two of the four units have
populations with moderate levels of resiliency.
The Virgin Islands boa has demonstrated some ability to adapt to
changing environmental conditions over time from both anthropogenic
threats (e.g., habitat disturbance due to development) and natural
disturbances (e.g., predation and hurricanes). Compared to the species'
distribution at the time of listing (see 35 FR 16047; October 13,
1970), which included three locations (Puerto Rico, St. Thomas, and
Tortola), the species currently has five populations (potentially more
if others are eventually confirmed). Two of the five current
populations exhibit moderate levels of resiliency, whereas three
exhibit moderately low to low resiliency. One other assessed population
is presumed extirpated (Cayo Ratones).
We note that, by using the SSA framework to guide our analysis of
the scientific information documented in the SSA report, we have not
only analyzed individual effects on the species, but we have also
analyzed their potential cumulative effects. We incorporate the
cumulative effects into our SSA analysis when we characterize the
current and future condition of the species. Our assessment of the
current and future conditions encompasses and incorporates the threats
individually and cumulatively. Our current and future condition
assessment is iterative because it accumulates and evaluates the
effects of all the factors that may be influencing the species,
including threats and conservation efforts. Because the SSA framework
considers not just the presence of the factors, but to what degree they
collectively influence risk to the entire species, our assessment
integrates the cumulative effects of the factors and replaces a
standalone cumulative effects analysis.
Future Conditions
Because we determined that the current condition of the Virgin
Islands boa is consistent with an endangered species (see Determination
of Status, below), we are not presenting the results of the future
scenarios in this withdrawal. For more information on the future
condition, future threats, and future scenarios for the Virgin Islands
boa, see the SSA report (Service 2022, pp. 36-60).
Determination of Virgin Islands Boa's Status
Section 4 of the Act (16 U.S.C. 1533) and its implementing
regulations (50 CFR part 424) set forth the procedures for determining
whether a species meets the definition of ``endangered species'' or
``threatened species.'' 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 a species meets the definition of
``endangered species'' or ``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.
Status Throughout All of Its Range
Compared to the species' distribution at the time of listing (see
35 FR 16047; October 13, 1970), which included three locations (Puerto
Rico, St. Thomas, and Tortola), Virgin Islands boa currently has five
extant populations (potentially more if others are eventually
confirmed), and one presumed extirpated population. None of the
populations exhibit high resiliency; only two of the six current
populations exhibit moderate level of resiliency (Cayo Diablo and USVI
Cay), one has moderately low resiliency (Culebra), two exhibit low
resiliency (Rio Grande and St. Thomas), and one is considered presumed
extirpated (Cayo Ratones). Recent surveys indicate that current
population trend estimates are either declining, potentially declining,
considered rare, or unknown and most populations are small or
considered rare (Service 2022, p. 30). Three of the populations are
currently impacted by habitat loss and degradation by development,
three populations are at high risk from storm surges, and three of five
populations are under imminent threat by exotic mammal predation. The
species does not have enough current redundancy, lacking highly
resilient populations and having only two moderately resilient
populations; thus, the species is at risk from catastrophic events. In
addition, as the species lacks multiple resilient populations that
contribute to the genetic diversity of the species, thus limiting
species representation or overall future adaptive capacity.
In summary, due to the new information we received during both of
the September 30, 2020, proposed rule's public comment periods and at
the May 12, 2021, public hearing, we find that there is no longer
sufficient evidence to justify reclassifying the Virgin Islands boa as
a threatened species, and the
[[Page 66360]]
species still meets the Act's definition of an endangered species. The
new information included the probable extirpation of Virgin Islands
boas due to colonization of rats on Cayo Ratones, and an error in
calculations affecting the current resiliency score for the Cayo Diablo
population. Based on our revised SSA report (Service 2022, entire)
incorporating this new information, estimates of current resiliency for
the Virgin Islands boa are low, as are estimates for representation and
redundancy. The Virgin Islands boa faces a variety of ongoing threats
from habitat loss and degradation from development, introduced
predators, SLR and a changing climate, and public attitudes towards
snakes. Given current rates of resiliency, populations are vulnerable
to extirpation from stochastic events, in turn, resulting in concurrent
losses in representation and redundancy. For these reasons, the Virgin
Islands boa is in danger of extinction throughout its range.
Status Throughout a Significant Portion of Its Range
Under the Act and our implementing regulations, a species may
warrant listing if it is in danger of extinction or likely to become so
in the foreseeable future throughout all or a significant portion of
its range. We have determined that the Virgin Islands boa is in danger
of extinction throughout all of its range and accordingly did not
undertake an analysis of any significant portion of its range. Because
the Virgin Islands boa warrants listing as endangered throughout all of
its range, our determination does not conflict with the decision in
Center for Biological Diversity v. Everson, 435 F. Supp. 3d 69 (D.D.C.
2020) (Everson), which vacated the provision of the Final Policy on
Interpretation of the Phrase ``Significant Portion of Its Range'' in
the Endangered Species Act's Definitions of ``Endangered Species'' and
``Threatened Species'' (79 FR 37578; July 1, 2014) providing that if
the Service determines that a species is threatened throughout all of
its range, the Service will not analyze whether the species is
endangered in a significant portion of its range.
Determination of Status
Our review of the best available scientific and commercial
information indicates that the Virgin Islands boa continues to meet the
Act's definition of an endangered species. Therefore, in accordance
with section 4(b)(6)(A)(i)(IV) of the Act, we withdraw our proposed
rule to reclassify the Virgin Islands boa as a threatened species with
a rule issued under section 4(d) of the Act.
References Cited
A complete list of references cited in this document is available
on the internet at <a href="https://www.regulations.gov">https://www.regulations.gov</a> and upon request from
the Caribbean Ecological Services Field Office (see FOR FURTHER
INFORMATION CONTACT).
Authors
The primary authors of this document are the staff members of the
Fish and Wildlife Service's Species Assessment Team and the Caribbean
Ecological Services Field Office.
Authority
The authority for this action is the Endangered Species Act of
1973, as amended (16 U.S.C. 1531 et seq.).
Martha Williams,
Director, U.S. Fish and Wildlife Service.
[FR Doc. 2023-20946 Filed 9-26-23; 8:45 am]
BILLING CODE 4333-15-P
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