# Endangered and Threatened Wildlife and Plants; Endangered Species Status for Puerto Rican Skink, Lesser Virgin Islands Skink, and Virgin Islands Bronze Skink and Designation of Critical Habitat; Threatened Species Status With Section 4(d) Rule for Culebra Skink and Designation of Critical Habitat; Not Warranted Species Status for Mona Skink, Greater Virgin Islands Skink, Greater Saint Croix Skink, and Lesser Saint Croix Skink

> Briefs, arguments, decisions, and more.

URL: https://www.frixlaw.com/law-library/documents/fr%3A2024-29125

## Record

- **Collection:** Federal Register
- **Document type:** Proposed Rule
- **Published:** December 19, 2024
- **Citation:** 89 FR 103938

## Text

DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
[Docket No. FWS-R4-ES-2024-0154; FXES1111090FEDR-256-FF09E21000]
RIN 1018-BH81
Endangered and Threatened Wildlife and Plants; Endangered Species Status for Puerto Rican Skink, Lesser Virgin Islands Skink, and Virgin Islands Bronze Skink and Designation of Critical Habitat; Threatened Species Status With Section 4(d) Rule for Culebra Skink and Designation of Critical Habitat; Not Warranted Species Status for Mona Skink, Greater Virgin Islands Skink, Greater Saint Croix Skink, and Lesser Saint Croix Skink

AGENCY:

Fish and Wildlife Service, Interior.

ACTION:

Proposed rule and notification of findings.

SUMMARY:

We, the U.S. Fish and Wildlife Service (Service), propose to list the Puerto Rican skink (
Spondylurus nitidus
), a skink species from Puerto Rico and Desecheo Island, and the Lesser Virgin Islands skink (
S. semitaeniatus
) and Virgin Islands bronze skink (
S. sloanii
), two skink species from the U.S. Virgin Islands and the British Virgin Islands, as endangered species. We propose to list the Culebra skink (
S. culebrae
), a skink species from Culebra Island and offshore cays of Puerto Rico, as a threatened species with protective regulations under section 4(d) of the Endangered Species Act of 1973, as amended (Act) (“4(d) rule”). After a review of the best available scientific and commercial information, we find that listing these species is warranted. If we finalize this rule as proposed, we will add these species to the List of Endangered and Threatened Wildlife and extend the Act's protections to these species. We also propose to designate critical habitat for the Puerto Rican skink, Culebra skink, Lesser Virgin Islands skink, and Virgin Islands bronze skink under the Act. We also announce the availability of an economic analysis of the proposed designation of critical habitat for the Puerto Rican skink, Culebra skink, Lesser Virgin Islands skink, and Virgin Islands bronze skink. We find that it is not warranted at this time to list the Mona skink (
Spondylurus monae
), the Greater Virgin Islands skink (
S. spilonotus
), the Greater Saint Croix skink (
S. magnacruzae
), and the Lesser Saint Croix skink (
Capitellum parvicruzae
). However, we ask the public to submit to us at any time any new information relevant to the status of any of the species mentioned above and their habitats.

DATES:

We will accept comments received or postmarked on or before February 18, 2025. Comments submitted electronically using the Federal eRulemaking Portal (see ADDRESSES, below) must be received by 11:59 p.m. eastern time on the closing date. We must receive requests for a public hearing, in writing, at the address shown in
FOR FURTHER INFORMATION CONTACT
by February 3, 2025.

ADDRESSES:

You may submit comments by one of the following methods:

(1)
Electronically:
Go to the Federal eRulemaking Portal:

https://www.regulations.gov.
In the Search box, enter FWS-R4-ES-2024-0154, 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, check the Proposed Rule box to locate this document. You may submit a comment by clicking on “Comment.”

(2)
By hard copy:
Submit by U.S. mail to: Public Comments Processing, Attn: FWS-R4-ES-2024-0154, U.S. Fish and Wildlife Service, MS: PRB/3W, 5275 Leesburg Pike, Falls Church, VA 22041-3803.

We request that you send comments only by the methods described above. We will post all comments on
https://www.regulations.gov.
This generally means that we will post any personal information you provide us (see Information Requested, below, for more information).

Availability of supporting materials:
Supporting materials, such as the species status assessment report, are available on the Service's website at
https://www.fws.gov/office/caribbean-ecological-services,
at
https://www.regulations.gov
at Docket No. FWS-R4-ES-2024-0154, or both.

FOR FURTHER INFORMATION CONTACT:

Lourdes Mena, Field Supervisor, U.S. Fish and Wildlife Service, Caribbean Ecological Services Field Office, P.O. Box 491, Boquerón, PR 00622; telephone 352-749-2462; email:
lourdes_mena@fws.gov.
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. Please see Docket No. FWS-R4-ES-2024-0154 on
https://www.regulations.gov
for a document that summarizes this proposed rule.

SUPPLEMENTARY INFORMATION:

Executive Summary

Why we need to publish a rule.
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 Puerto Rican skink, Lesser Virgin Islands skink, and Virgin Islands bronze skink meet the Act's definition of endangered species and the Culebra skink meets the definition of a threatened species; therefore, we are proposing to list them as such and propose designation of critical habitat for each species. Both listing a species as an endangered or threatened species and making a critical habitat designation 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.
We propose to add the Puerto Rican skink, Lesser Virgin Islands skink, and Virgin Islands bronze skink as endangered species to the List of Endangered and Threatened Wildlife (List) in title 50 of the Code of Federal Regulations at 50 CFR 17.11. We also propose adding the Culebra skink as a threatened species to the List with a rule under section 4(d) of the Act, and we propose the designation of critical habitat for all of these species. This document serves as our 12-month petition findings for the Puerto Rican skink, Lesser Virgin Islands skink, Virgin Islands bronze skink, and the Culebra skink. We also announce 12-month petition findings that the Mona skink, Greater Virgin Islands skink, Greater Saint Croix skink, and Lesser Saint Croix skink are not warranted for listing as endangered or threatened species under the Act.

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 Puerto Rican skink, Lesser Virgin Islands skink, and Virgin Islands bronze skink are endangered species due to the following threats: nonnative predators (Factor C) and habitat loss and degradation from development (Factor A). We have determined that the Culebra skink is a threatened species due to the following threats: nonnative predators (Factor C), habitat loss and degradation from development (Factor A), and sea level rise and storm surge from a changing climate (Factor E).

Section 4(a)(3) of the Act requires the Secretary of the Interior (Secretary), to the maximum extent prudent and determinable, concurrently with listing designate critical habitat for the species. Section 3(5)(A) of the Act defines critical habitat as (i) the specific areas within the geographical area occupied by the species, at the time it is listed, on which are found those physical or biological features (I) essential to the conservation of the species and (II) which may require special management considerations or protections; and (ii) specific areas outside the geographical area occupied by the species at the time it is listed, upon a determination by the Secretary that such areas are essential for the conservation of the species. Section 4(b)(2) of the Act states that the Secretary must make the designation on the basis of the best scientific data available and after taking into consideration the economic impact, the impact on national security, and any other relevant impacts of specifying any particular area as critical habitat.

Information Requested

We intend that any final actions resulting from this proposed rule will be based on the best scientific and commercial data available and be as accurate and as effective as possible. Therefore, we request comments or information from other governmental agencies, Native American Tribes, the scientific community, industry, or any other interested parties concerning this proposed rule. We particularly seek comments concerning:

(1) Each skink species' biology, ranges, and population trends, including:

(a) Biological or ecological requirements of the species, including habitat requirements for feeding, breeding, and sheltering;

(b) Genetics and taxonomy;

(c) Historical and current ranges, including distribution patterns and the locations of any additional populations of these species;

(d) Historical and current population levels, and current and projected trends; and

(e) Past and ongoing conservation measures for these species and/or their habitats.

(2) Threats and conservation actions affecting the species, including:

(a) Factors that may be affecting the continued existence of the species, which may include habitat modification or destruction, overutilization, disease, predation, the inadequacy of existing regulatory mechanisms, or other natural or manmade factors.

(b) Biological, commercial trade, or other relevant data concerning any threats (or lack thereof) to these species.

(c) Existing regulations or conservation actions that may be addressing threats to these species.

(3) Additional information concerning the historical and current status of these species.

(4) Information to assist us with applying or issuing protective regulations under section 4(d) of the Act that may be necessary and advisable to provide for the conservation of the Culebra skink, in particular, whether we should consider any additional or different exceptions from the prohibitions in the 4(d) rule.

(5) Specific information related to critical habitat, such as:

(a) The amount and distribution of Puerto Rican skink, Culebra skink, Lesser Virgin Islands skink, and Virgin Islands bronze skink habitat;

(b) Any additional areas occurring within the range of each of the species, including Puerto Rico and surrounding islands and cays as well as the U.S. Virgin Islands and British Virgin Islands, that should be included in the designation because they (i) are occupied at the time of listing and contain the physical or biological features that are essential to the conservation of the species and that may require special management considerations or protection, or (ii) are unoccupied at the time of listing and are essential for the conservation of the species;

(c) Special management considerations or protection that may be needed in critical habitat areas we are proposing, including managing for the potential effects of predators and climate change; and

(d) Whether areas not occupied at the time of listing qualify as habitat for the species and are essential for the conservation of the species.

(6) Land use designations and current or planned activities in the subject areas and their possible impacts on proposed critical habitat.

(7) Any probable economic, national security, or other relevant impacts of designating any area that may be included in the final designation, and the related benefits of including or excluding specific areas.

(8) Information on the extent to which the description of probable economic impacts in the economic analyses is a reasonable estimate of the likely economic impacts and any additional information regarding probable economic impacts that we should consider.

(9) Whether any specific areas we are proposing for critical habitat designation should be considered for exclusion under section 4(b)(2) of the Act, and whether the benefits of potentially excluding any specific area outweigh the benefits of including that area under section 4(b)(2) of the Act. If you think we should exclude any additional areas, please provide information supporting a benefit of exclusion.

(10) Whether we could improve or modify our approach to designating critical habitat in any way to provide for greater public participation and understanding, or to better accommodate public concerns and comments.

Please include sufficient information with your submission (such as scientific journal articles or other publications) to allow us to verify any scientific or commercial information you include.

Please note that submissions merely stating support for, or opposition to, the action under consideration without providing supporting information, although noted, do not provide substantial information necessary to support a determination. Section 4(b)(1)(A) of the Act directs that determinations as to whether any species is an endangered or a threatened species must be made solely on the basis of the best scientific and commercial data available, and section 4(b)(2) of the Act directs that the Secretary shall designate critical habitat on the basis of the best scientific data available.

You may submit your comments and materials concerning this proposed rule by one of the methods listed in
ADDRESSES
. We request that you send comments only by the methods described in
ADDRESSES
.

If you submit information via
https://www.regulations.gov,
your entire submission—including any personal identifying information—will be posted

on the website. If your submission is made via a hardcopy that includes personal identifying information, you may request at the top of your document that we withhold this information from public review. However, we cannot guarantee that we will be able to do so. We will post all hardcopy submissions on
https://www.regulations.gov.

Comments and materials we receive, as well as supporting documentation we used in preparing this proposed rule, will be available for public inspection on
https://www.regulations.gov.

Our final determination may differ from this proposal because we will consider all comments that we receive during the comment period as well as any information that may become available after this proposal. Based on the new information that we receive (and, if relevant, any comments on that new information), we may conclude that the Puerto Rican skink, Lesser Virgin Islands skink, or Virgin Islands bronze skink are threatened instead of endangered species, or that the Culebra skink is an endangered species instead of a threatened species, or we may conclude that these species do not warrant listing as either endangered species or threatened species. For critical habitat, our final designation may not include all areas proposed, may include some additional areas that meet the definition of critical habitat, or may exclude some areas if we find the benefits of exclusion outweigh the benefits of inclusion and exclusion will not result in the extinction of the species. In addition, we may change the parameters of the prohibitions or the exceptions to those prohibitions in the protective regulations issued or applied under section 4(d) of the Act for Culebra skink if we conclude it is appropriate in light of comments and new information received. For example, we may expand the prohibitions if we conclude that the protective regulations as a whole, including those additional prohibitions, are necessary and advisable to provide for the conservation of the Culebra skink. Conversely, we may establish additional exceptions to the prohibitions in the final rule if we conclude that the activities would facilitate or are compatible with the conservation and recovery of the Culebra skink. In our final rule, we will clearly explain our rationale and the basis for our final decision, including why we made changes, if any, that differ from this proposal.

Public Hearing

Section 4(b)(5) of the Act provides for a public hearing on this proposal, if requested. Requests must be received by the date specified in
DATES
. Such requests must be sent to the address shown in
FOR FURTHER INFORMATION CONTACT
. We will schedule a public hearing on this proposal, if requested, and announce the date, time, and place of the hearing, as well as how to obtain reasonable accommodations, in the
Federal Register
and local newspapers at least 15 days before the hearing. We may hold the public hearing in person or virtually via webinar. We will announce any public hearing on our website, in addition to the
Federal Register
. The use of virtual public hearings is consistent with our regulations at 50 CFR 424.16(c)(3).

Previous Federal Actions

On February 11, 2014, we received a petition from the Center for Biological Diversity (CBD) and Dr. Renata Platenberg (reptile ecologist) requesting that nine Caribbean skink species be listed as endangered or threatened and that critical habitat be designated for these species under the Act. These nine species are: the Puerto Rican skink, the Culebra skink, the Mona skink, the Monito skink, the Greater and Lesser Virgin Islands skinks, the Virgin Islands bronze skink, and the Greater and Lesser Saint Croix skinks. We acknowledged receipt of this petition via email on February 12, 2014. On January 12, 2016, we published a positive 90-day finding (81 FR 1368) indicating that the petitioned action may be warranted and that the petition presented substantial scientific or commercial information for seven of the skink species. On March 16, 2016, we published a not-substantial 90-day finding (81 FR 14058) for Monito skink. On September 14, 2016, we published a substantial 90-day finding (81 FR 63160) for the Lesser Virgin Islands skink.

On March 10, 2020, CBD issued a notice of intent to file suit to compel the Service to issue 12-month findings for the eight skinks with substantial 90-day findings. On September 22, 2020, CBD filed a complaint for declaratory and injunctive relief, stating that the Service had failed to make a timely determination for whether the eight species of Caribbean skink warrant protection under the Act. On May 27, 2021, the Service agreed to a settlement to complete its review of the status of the skinks and submit 12-month findings to the
Federal Register
by December 12, 2024.

Peer Review

A species status assessment (SSA) team prepared an SSA report for the Puerto Rican skink, Mona skink, Culebra skink, Greater Virgin Islands skink, Lesser Virgin Islands skink, Virgin Islands bronze skink, Greater Saint Croix skink, and Lesser Saint Croix skink (Service 2023, entire). The SSA team was composed of Service biologists and a contractor from Texas A&M University, in consultation with other species experts. The SSA report represents a compilation of the best scientific and commercial data available concerning the status of each of the species, including the impacts of past, present, and future factors (both negative and beneficial) affecting each of the species.

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 (
https://www.fws.gov/sites/default/files/documents/peer-review-policy-directors-memo-2016-08-22.pdf
), we solicited independent scientific review of the information contained in the SSA report. We sent the SSA report to seven independent peer reviewers and received three responses. Results of this structured peer review process can be found at
https://www.regulations.gov.
In preparing this proposed rule, we incorporated the results of these reviews, as appropriate, into the SSA report, which is the foundation for this proposed rule.

Summary of Peer Reviewer Comments

As discussed in Peer Review above, we received comments from three peer reviewers on the draft SSA report. We reviewed all comments we received from the peer reviewers for substantive issues and new information regarding the contents of the SSA report. The peer reviewers generally concurred with our methods and conclusions and provided clarifications and editorial suggestions. One reviewer indicated the Service was not justified in concluding that the Puerto Rican skink does not inhabit Culebra, Cayo Norte, and Cayo Luis Pena. The Service acknowledges it is possible that the Puerto Rican skink may have been in these locations historically; however, we lack genetic information that could confirm Puerto Rican skinks are sympatric with Culebra skinks. The SSA report provides this background in the historical distribution narrative (Service 2023, p. 33) but does not include Puerto Rican skinks in the distribution maps for these areas. We also received a comment disagreeing with information presented in appendix B of the SSA report (Service 2023, pp. 146-169) summarizing the likely extinct status of the Greater Virgin Islands skink, Greater Saint Croix skink, and

Lesser Saint Croix skink, referencing the discrepancy with the International Union for Conservation's (IUCN) criterion for possible extinction. The Service does not use the IUCN criterion to determine whether a species is extinct. The Service used the best available information, as presented in the SSA report, to determine that these species are extinct. Otherwise, no substantive changes to our analysis and conclusions within the SSA report were deemed necessary, and peer review comments are addressed in version 1.0 of the SSA report.

I. Proposed Listing Determination

Background

A thorough review of the taxonomy, genetics, life history, and ecology of each of the skink species is presented in the SSA report (Service 2023, pp. 17-43), and species-specific distribution information follows the general overview below.

The eight Caribbean skink species—Puerto Rican skink, Mona skink, Culebra skink, Greater Virgin Islands skink, Lesser Virgin Islands skink, Virgin Islands bronze skink, Greater Saint Croix skink, and Lesser Saint Croix skink—have similar patterns and coloration. All are generally some shades of tans and browns, with a pair of dark lateral stripes and limb pattern, if present, with spots or blotches (Hedges and Conn 2012, pp. 14-15). Juveniles often have blue tails. Available information suggests that females are slightly larger than males (Hedges and Conn 2012, p. 10). Adult snout-vent length (SVL) will also differ slightly between species, but in general ranges from approximately 3 to 4 inches (in) (7.6 to 10 centimeters (cm)).

Caribbean skinks are ectothermic (cold-blooded) animals and therefore highly dependent on the air and soil temperature to thermoregulate (maintain body core temperature) (Noble et al. 2017, p. 72) and are often observed basking in the sun on rocks, leaf litter, and fallen logs in forest habitat (Henderson and Powell 2009, p. 293; Sanchez 2013, p. 1). Caribbean skinks have been observed on the ground, shrubs, cacti, trees, boulder and limestone rocks, leaf litter, on and under debris piles, under rocks and rock fissures, near human habitation and houses, and are known to hide from perceived predators under or within rocks, vegetation, and debris or when they are not basking (Bullock and Evans 1990, p. 428; Henderson and Powell 2009, pp. 292-293, Hedges and Conn 2012, entire).

Very little information exists about the diet and foraging behavior of Caribbean skinks. They appear to be diurnal and primarily hunt for prey by actively foraging in dry coastal woodlands but are known to be somewhat omnivorous including consumption of some plants (Platenberg and Boulon 2006, p. 224; Daudin and de Silva 2011, p. 265; Henderson and Powell 2009, pp. 292-293; Hedges and Conn 2012, p. 220). Some information specifies that the skink diet is omnivorous, including insects, fruits, and even a common coqui (
Eleutherodactylus coqui
) in Puerto Rico (Henderson and Powell 2009, p. 293).

Caribbean skinks are viviparous (
i.e.,
bearing live young). It is theorized that the timing of birth in viviparous skinks is meant to maximize food availability (Vrcibradic and Rocha 2011, p. 822; Hedges and Conn 2012, p. 223) as well as maximize optimal conditions for growth and survival of neonates (Abts 1988, p. 389; Olsson and Shine 1997, entire). Most skink species reproduce annually, but many skinks have more than one brood; however, it is unknown which reproductive strategy is exhibited in female Caribbean skinks. Collection of specimens indicates Caribbean skinks are gravid during the dry season, which is January through April, and birthing occurs primarily in February through May (Hedges and Conn 2012, p. 223). Little information is available about the influences on fecundity of Caribbean skinks. Given that
Spondylurus
reproductive strategy is similar to other viviparous skinks, maternal thermoregulation (
i.e.,
basking behavior) is likely used by female Caribbean skinks to keep developing embryos at optimal temperatures for development of the young. Therefore, influences on basking time of female skinks (
e.g.,
the presence of predators) could have the potential to decrease the fecundity of Caribbean skinks or decrease the survival of young skinks.

No population estimates are available for the eight skink species. During 2021-2022 skink surveys (Rivera et al. 2023, p. 9), there were 42 observations of Puerto Rican skinks, 8 of Mona skinks, 59 of Culebra skinks, and 4 of Virgin Islands bronze skinks. In addition, on Desecheo Island, five Puerto Rican skinks were encountered during a 6-day herpetological survey (Herrera-Giraldo and Bermudez 2010, p. 22).

Current and historical distributions of the eight Caribbean skink species encompass the islands of Puerto Rico, the U.S. Virgin Islands (USVI), and the British Virgin Islands (BVI). The Puerto Rican skink, the Mona skink, and the Culebra skink all fall within the U.S. territory of Puerto Rico, which includes the main island of Puerto Rico and surrounding islands (figure 1). The Puerto Rican skink's current range includes the main island of Puerto Rico and Desecheo (figure 1).

BILLING CODE 4333-15-P

EP19DE24.000

The Mona skink occurs on only one island, Mona Island, off the west coast of Puerto Rico (figure 1). The current range of the Culebra skink encompasses the island of Culebra and its surrounding cays (Cayo Agua, Cayo Botella, Cayo Lobito, and Cayo Yerba), all occurring to the east of the main island of Puerto Rico (figure 1).

EP19DE24.001

Species that did occur entirely within the USVI include the Greater Virgin Islands skink (figure 2), the Greater Saint Croix skink (figure 3), and the Lesser Saint Croix skink (figure 3), all of which are considered likely extinct. The species that occur in both the USVI and BVI include the Lesser Virgin Islands skink and the Virgin Islands bronze skink (figure 2). The Lesser Virgin Islands skink has the largest range of all the Caribbean skink species and still occurs in both the USVI (Hans Lollik) and BVI (Guana Island, Mosquito Island, Tortola) (figure 2). The Virgin Islands bronze skink also had a larger range but is now confined to a few small to medium sized islands in the USVI (Buck Island, Water Island, Turtledove Cay; figure 2).

EP19DE24.002

BILLING CODE 4333-15-C
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.

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 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.

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, which is further described in the 2009 Memorandum Opinion on the foreseeable future from the Department

of the Interior, Office of the Solicitor (M-37021, January 16, 2009; “M-Opinion,” available online at
https://www.doi.gov/sites/doi.opengov.ibmcloud.com/files/uploads/M-37021.pdf
). The foreseeable future extends as far into the future as the U.S. Fish and Wildlife Service and National Marine Fisheries Service (hereafter, the Services) can make reasonably reliable predictions about the threats to the species and the species' responses to those threats. We need not identify the foreseeable future in terms of a specific period of time. We will describe the foreseeable future on a case-by-case basis, using the best available data and taking into account considerations such as the species' life-history characteristics, threat projection timeframes, and environmental variability. In other words, the foreseeable future is the period of time over which we can make reasonably reliable predictions. “Reliable” does not mean “certain”; it means sufficient to provide a reasonable degree of confidence in the prediction, in light of the conservation purposes of the Act.

Analytical Framework

The SSA report 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 our decision on whether the species should be proposed for listing as an endangered or threatened species under the Act. However, it does 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 Puerto Rican skink, Mona skink, Culebra skink, Greater Virgin Islands skink, Lesser Virgin Islands skink, Virgin Islands bronze skink, Greater Saint Croix skink, and Lesser Saint Croix skink viability, 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, 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, which we then used to inform our regulatory decision.

The following is a summary of the key results and conclusions from the SSA report; the full SSA report can be found at Docket No. FWS-R4-ES-2024-0154 on
https://www.regulations.gov.

Summary of Biological Status and Threats

In this discussion, we review the biological condition of each species and their resources, and the threats that influence the species' current and future conditions, in order to assess the species' overall viability and the risks to that viability.

Individual, Population, and Species Needs

At the individual level, skinks require suitable foraging, basking, and shelter habitat to survive during each life stage from birth to adulthood, and to successfully reproduce. Individual needs of Caribbean skink species are: (1) trees, shrubs, bushes ground cover/leaf litter, cacti, debris, rocks, and crevices for shelter; (2) basking locations for thermoregulation; and (3) arthropods as a food source (Service 2023, p. 44). Suitable habitat contains substrate that provides refugia, presence of vegetation, vertical spaces, and areas that offer both canopied and exposed sections for basking.

Skink populations are defined as single island units except for mainland Puerto Rico (see
Current Condition Methods,
below). For populations to demonstrate resiliency, the needs of individual skinks must be met at a larger scale. Specific demographic information on population carrying capacity, birth rates, and reproductive success is lacking for these species. It can be inferred from individual needs that an interbreeding population requires the elements needed by individuals in sufficient quantities and configuration to support multiple individuals and life stages. Given the small size of skink species, patches that can support a population are expected to be relatively small (~3 ac (1.2 ha)), based on the size of the smallest occupied cays. In addition, while there are skink populations that have persisted alongside nonnative predators like cats or rats, in general, populations show higher resiliency where predators are few or absent. Further, nonnative predators are currently absent from small cays where skink populations have persisted (Service 2023, p. 45).

For species' viability, there must be adequate redundancy (number of resilient populations with distribution and connectivity to allow the species to withstand catastrophic events) and representation (genetic and environmental diversity to allow the species to adapt to changing environmental conditions). The minimum number of resilient populations necessary to sustain each skink species is unknown, but we assume that populations with low resiliency contribute negligibly to overall species' viability. As island species, the relatively small, patchily distributed, and isolated cays can each support only small numbers of individuals (or separate populations). Redundancy improves with increasing numbers of populations distributed across the species' range, and connectivity allows connected populations to “rescue” each other after catastrophes. The level of redundancy (distribution) operating within a species is determined by the resiliency (abundance and health) of its populations. Representation, or adaptive capacity, improves with increased genetic and/or ecological diversity within and among populations. Long-term viability requires resilient populations in locations that are protected from the long-term catastrophic but permanent effects of climate change (
e.g.,
sea level rise and effects from catastrophic hurricanes claiming low-lying habitat) and invasion of nonnative predators.

Influences

Influences on the Caribbean skink species vary by location, but threats include nonnative predators, habitat

loss and degradation from development, and sea level rise and storm surge from a changing climate. Positive influences on the Caribbean skink species viability are habitat protection and predator control.

Nonnative Predators

A primary threat to Caribbean skink populations is the presence of nonnative predators including cats (
Felis catus
), rats (
Rattus
sp.), and mongooses (
Herpestes javanicus
or
Urva auropunctata
).

Mongooses are implicated in the decline and loss of several Caribbean skink species (Hedges and Conn 2012, pp. 224-229). Mongooses were introduced to the Caribbean during the late 19th and early 20th centuries with the goal of reducing rat populations. However, the presence of mongooses did not decrease rat densities, and mongooses have become a predator of many native vertebrate and invertebrate species in the Caribbean, including lizards (Wolcott 1953, entire; Witmer et al. 1998, p. 282; Henderson 1992, p. 3). Other reptile species with similar life history traits that are also endemic in the Caribbean have been shown to be vulnerable to mongoose depredation. For example, the endangered St. Croix ground lizard was extirpated from the main island of St. Croix in the 1900s, in part due to mongoose predation (Angeli and Fitzgerald 2021, p. 345). Lizards from the genus
Ameiva
(whiptail lizards) and snakes from the genera
Alsophis
(racers) are also susceptible to mongoose predation because they are diurnal, ground-dwelling, oviparous, active foragers, relatively small (Henderson 1992, p. 7), and easily caught by mongooses. Other than laying eggs (oviparity), these characteristics are shared by the Caribbean skink species.

Feral cats have occurred for hundreds of years throughout the Caribbean near human development and are known to be predators of reptiles on numerous islands (Henderson 1992, p. 2; Service 2023, pp. 46-47). Cats are instinctively natural predators and have been documented killing a variety of lizard species including five-lined skinks (
Plestiodon fasciatus
), broad-headed skinks (
P. laticeps),
and ground skinks (
Scincella lateralis
) (Mitchell and Beck 1992, p. 200). Cats are documented to have preyed on the Mona skink (López-Torres and García 2013, entire) and the Puerto Rican skink (González 2023, pers. comm.).

Rats are known to depredate small lizards on many islands, including the St. Lucia whiptail lizard (
Cnemidophorous vanzoi
), the Belize leaf-tailed gecko (
Phyllodactylus insularis
) on Half Moon Cay, and blue-tailed skinks (
Cryptoblepharus egeriae
) on Christmas Island (Harper and Bunbury 2015, p. 616). However, the influence of rats on skink populations is unclear. Despite being omnivorous, rats' primary food on islands is arthropods and plants, suggesting that rats may be consuming the food sources of the skinks as well as depleting local vegetation. This consumption would lower the suitability of the habitat while also increasing depredation on the skinks themselves (Harper and Bunbury 2015, pp. 614, 616). Rats have a much more profound effect on skink populations that occur on very small islands and cays. Furthermore, rats are consistently introduced to islands, as they are easily transported by boats (Harper and Bunbury 2015, entire).

Besides direct predation, skinks (as prey) may respond to the presence of predators by increasing their time seeking refuge at the cost of foraging, thermoregulation, and mating (Sih 1994, entire). Further, prey may be less adapted to changes in these pressures because these are introduced species (Martín and López 1999, p. 491). The impacts from nonnative predators are likely more severe on smaller islands because there is often a lower diversity of prey items for predators (Henderson 1992, p. 5).

Habitat Loss and Degradation

Caribbean skinks occur on both private and publicly owned land. Where skinks occur in urban or rural areas, habitat loss and degradation resulting from development is a threat to populations. This is the case for Puerto Rico, Culebra, and the main developed islands in USVI and BVI. For example, in Puerto Rico, human activity has been described as “intensive, pervasive, and fragments natural habitat” (Lugo and Helmer 2004, p. 156). This is particularly true in the northern and eastern portions of the main island of Puerto Rico; however, the central and southern portions of the main island remain largely undeveloped (Gould et al. 2008, p. 91; see figure 4.3 in SSA report (Service 2023, p. 49)). Lands cleared for development would essentially eliminate potential habitat for the skinks and may directly kill individuals as well, particularly if development occurs in or adjacent to suitable skink habitat. And although forest areas have increased in Puerto Rico, unprotected forested areas are vulnerable to urban development, particularly those near or within urban centers (Kennaway and Helmer 2007, p. 376). In the USVI as well, human population growth has resulted in habitat loss and degradation of natural habitats, and most land is privately owned (Platenberg and Boulon 2006, p. 217).

Skinks are now absent from completely developed urban landscapes that are not adjacent to natural habitat; however, skinks have been seen in and around rural residential areas in Puerto Rico within karst habitat and in residential and developed areas in Culebra (Zegarra 2023, pers. comm.). This could be due to “urban survival” of the skinks, which is the idea that mongooses are less abundant in areas with larger human inhabitation because they are depredated by other nonnatives (
e.g.,
dogs; Hedges and Conn 2012, p. 228). Skinks have also been observed using debris piles (
i.e.,
vegetation and trash) accumulated on the side of roads and trails adjacent to forested habitat, and on human-made rock piles for road construction. As skink habitat is developed and encroached upon, observations of skinks in residential areas may become more common. However, skinks that occur within these areas are more susceptible to impacts from habitat loss as well as more susceptible to nonnative predators or competitors introduced by humans. While deforestation and fragmentation result from development, the extent of impacts to Caribbean skinks may range from low to high depending on each landscape as well as potential increased interactions with nonnative predators causing potential declines in skinks.

Climate Change: Sea Level Rise and Storm Surge

One of the stressors affecting Caribbean skinks and their habitat is the shift in climate impacts occurring because of increasing greenhouse gas (GHG) emissions. The long-term persistence of several small cays in the Caribbean is being challenged by rising sea levels and the increased intensity of storm surges. The main stressors to the skinks and their habitat resulting from climate change are sea level rise (SLR) and increased storm surges.

Relative sea levels have risen approximately 2 mm (0.08 in) per year in Puerto Rico and USVI since mid-20th century, and the rate or rise has been accelerating since the early 2000s (PRCCC 2022, p. 27). This recent acceleration suggests that, of the National Oceanic and Atmospheric Administration (NOAA) SLR scenarios based on different GHG emission scenarios (Sweet et al. 2017, pp. 21-22), the intermediate to high SLR scenarios are more likely to occur than the low and intermediate-low scenarios (Sweet et al. 2017, pp. 33-35; Sweet et al. 2022,

p. 12). For Puerto Rico, the near-term range at 2050 is 1 foot (ft) (0.3 meter (m)) for the intermediate local SLR scenario and 1.6 ft (0.5 m) for the high SLR scenario, and by 2100, the range is projected to be 3.3 ft (1.0 m) for the intermediate SLR scenario and 6.6 ft (2.0 m) for the high SLR scenario (NOAA 2023, entire). Most of the impacts of SLR on Caribbean skinks will likely occur on low-lying cays in the region, beginning with increased saltwater flooding events from more frequent storms.

Most measures of Atlantic hurricane activity have increased substantially since the early 1980s, the period during which high-quality satellite data are available (Service 2023, p. 52). These include measures of intensity, frequency, and duration as well as the number of strongest (Category 4 and 5) storms (Walsh et.al. 2014, p. 20). In the future, there is high confidence that SLR will increase storm inundation levels, and medium to high confidence that both precipitation rates and storm intensity will increase in hurricanes globally. In addition, there is medium to high confidence that the proportion of very strong storms (Category 4 and 5) will increase, but less confidence in increased frequency of storms overall (Knutson et al. 2020, p. E303). Strong rainstorms, tropical storms, and hurricanes are natural parts of a tropical ecosystem. However, with intensity, inundation levels, and precipitation all likely to increase, small patches and low-lying habitats are likely at risk. The resiliency of Caribbean skink species will likely be affected in these areas when the quantity and quality of their resources (food, cover) are compromised, particularly if there is not time to recover from previous events or areas are continually reduced over time.

Saltwater surges and short-term flooding of upland habitats from strong storms and hurricanes on low-lying cays likely have and will continue to influence Caribbean skink persistence (Díaz et al. 2022, p. 66). The severity and duration of hurricane impacts to Caribbean skinks and their habitat vary based on the intensity and scale of these storm events. Localized impacts can vary greatly depending upon not only the strength of the storm, but the direction of its approach and how quickly it moves through the area. Storm surges and their intensity can also vary depending on location. In 2017, nine named storms impacted the Caribbean, including Hurricanes Irma and Maria (both Category 5). Irma caused catastrophic storm surges in the USVI although the peak water level is unknown because the tidal gauges in the area went offline during the storm. Storm tides from Maria measured between 6 ft to 9 ft (1.5 m to 2.7 m) above mean sea level in southwestern Puerto Rico (FEMA 2018, p. i).

Impacts from heavy rainstorms, tropical storms, and hurricanes are part of this tropical islands system. The heavy inundation and even complete overwash of some islands during hurricanes may provide some explanation for the lack of skinks being observed, even when the island has recovered and again contains high-quality suitable skink habitat. Thus, storm events are likely a contributing factor to the low occurrence (historical and current) observed for several of the skink species. Individual skinks may colonize and occupy smaller islands only temporarily until storm events impact that island. Eventual recolonization of impacted islands by skinks is uncertain. Over time, storms could be a factor reducing the persistence of skink populations and thereby reducing the redundancy of the species.

Conservation Efforts and Regulatory Mechanisms

We do not know of any skink-focused conservation actions or efforts. However, any past, current, and future eradication or control of nonnative species is beneficial for the skinks. For example, efforts to control mongoose populations on St. Thomas, St. John, and St. Croix have been attempted, and rats and mongooses were completely eradicated on Buck Island, St. Thomas, USVI (Barun et al. 2011, p. 20). Rats were also eradicated from Monito Island, eliminating that predation threat for the Monito skink and other species on that island (García et. al 2002, entire). Monkeys, goats, and rats were also eradicated from Desecheo Island, a National Wildlife Refuge (Will et al. 2019, entire). Eradication of pigs, cats, and possibly rats is being planned for Mona Island (Service 2023, entire). Permanent eradication of nonnatives is typically most effective on small islands that do not have human development.

As skinks occur both on private and public lands, areas designated as nature reserves or refuges provide high-quality skink habitat as well as protection from development. For example, some of the most consistent skink observations for the Puerto Rican skink are from the Guajataca and Maricao Commonwealth Forests, two areas managed for conservation by the Puerto Rico Department of Natural and Environmental Resources (PRDNER). Skinks were also observed within the Montadero Natural Protected Area (Quebradillas Municipality, Puerto Rico) managed by the Puerto Rico Conservation Trust. Some of these karst forests are contained within the larger Karst Conservation Zone, a large area in Puerto Rico with stricter land regulations named the Karst Restricted Zone designated by the Puerto Rico Planning Board (Ortiz-Maldonado et al. 2019, entire). This Zone represents 7.2 percent (647 km
2
) of the total area of Puerto Rico, includes both public and private lands, and was designated as such for conservation purposes by prohibiting land exploitation of any type (Castro-Prieto et al. 2019, p. 59).

The Mona skink has a wide distribution within the Mona Island Nature Reserve, managed for conservation by the PRDNER. The Puerto Rican skink has been reported from the Desecheo NWR, and the Culebra skink occurs within the Culebra NWR specifically within the Monte Resaca area and some of its offshore cays (
i.e.,
Cayo Botella, Cayo Agua, Cayo Lobito, Cayo Yerba).

However, protected habitat does not ensure persistence of skinks, particularly if nonnative mammals are present. Rather, it suggests that habitat destruction or modification in those areas is minimal and less than for habitat that is not protected. For example, the Culebra skink was historically reported from Culebrita Island (part of the Culebra NWR) but is currently considered likely extirpated, most likely due to presence of rats.

Cumulative Effects

We note that, by using the SSA framework to guide our analysis of the scientific information documented in the SSA report, we have analyzed the cumulative effects of identified threats and conservation actions on the species. To assess the current and future condition of the species, we evaluate the effects of all the relevant 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.

Current Condition Methods

We considered all skinks within each island or cay (
i.e.,
outside of mainland Puerto Rico) to be single populations. We assume that each island is geographically isolated and the influences on and threats to Caribbean skinks tend to occur to entire islands

(
e.g.,
nonnative predators are either present or not present). Geographic ranges (
i.e.,
islands considered in these analyses outside of the main island of Puerto Rico) are based on current and historical records of each species.

As for the other Caribbean skink species, limited information is available on the distribution of Puerto Rican skinks on the main island of Puerto Rico. Therefore, we delineated the populations of the Puerto Rican skink on the main island using the recently (2021-2023) collected survey and genetic information to discern what areas could constitute separate populations (Rivera et al 2023, pp. 15-16). Genetic information was obtained via tail clips during surveys. We overlayed populations with potential habitat identified by the Puerto Rico GAP Analysis Project (PRGAP) for the species (Gould et al. 2008, p. 91). Predicted habitat from the GAP model utilized landcover types (
i.e.,
dry forest, woodland, and shrublands) in 2001 that were restricted to at or below 300 m and the few point locations for skinks that were available in 2006. The model is likely not comprehensive given the low number of confirmed skink observations that were available in 2006 and does not include the urban development that has occurred on the main island of Puerto Rico since 2001; we modified the model to include habitats below 500 m based on more recent survey locations and combined it with more recent genetic information from 2021-2023.

Numerous islands with historical skink records have not been surveyed recently, and it is possible that additional individuals and populations are present on these islands or even other islands in the Caribbean. Current data suggest that these species are habitat generalists. Some areas are likely not suitable as habitat for skinks, for example, entirely developed urban areas. However, skinks are also known to occur within some developed and rural areas, particularly if adjacent to suitable habitat. Thus, we considered an island with documented occurrences as a single population, except for mainland Puerto Rico, and we assessed habitat conditions based on characteristics of the entire island. On mainland Puerto Rico, we determined population status based on confirmed occurrence information and amount of potential habitat as determined by the Puerto Rico GAP analysis predicted habitat (Gould et al. 2008, p. 91); these populations were confirmed using the survey and genetic information (Rivera et al. 2023, pp. 15, 16). Survey methodology and reporting has varied significantly from population to population. Even with the same methodology and reporting, survey success can differ based on external factors like weather conditions, surveyor experience, detection probabilities, threats, or habitat conditions. All these factors contribute to high levels of uncertainty in the presence or absence of skinks within a population.

For each island population, we considered the population “extant” if skinks have been detected there since 2000. The threshold of detection before and after 2000, along with a Bayesian estimate of occurrence, which is a probabilistic model linking skink occurrence to several variables, such as predator presence, island size, maximum elevation, habitat class, human population size, and co-occurring species (see section 5.1.1 of SSA report (Service 2023, pp. 57-59), allows for a more conservative estimate of occurrence (
i.e.,
avoidance of classifying a population as extirpated when it is, in fact, extant). Because extensive surveys have not occurred on islands within the geographic ranges of many of the Caribbean skink species, we utilized Bayesian analyses to assess likelihood of skink existence on individual smaller islands (<5 square kilometers (km
2
) (500 ha)) with detections pre-2000 to assess if a skink population likely currently occurs there. If a smaller island was known to be occupied by skinks before 2000 and had a Bayesian probability score of ≤0.49, then we considered the status of that island “likely extirpated” and if the score is ≥0.50, we considered the status “unknown.” The exception to this was when islands had been extensively surveyed since 2000 and there have been no detections. Caribbean skinks are cryptic and difficult to detect, and the potential habitats on the larger islands are often difficult to access or survey thoroughly, and predators on some larger islands have seemingly already eliminated skinks (
i.e.,
St. Thomas, St. John, and St. Croix). Additionally, there are few case studies for larger islands for the Bayesian analysis, and the resulting network (
i.e.,
output from analysis) linking variables did a poor job predicting probability of existence on islands >5 km
2
(500 ha); therefore, we did not try to estimate status of populations on larger islands and considered all islands >5 km
2
with detections from between 1970 and 2000 to have an “unknown” status (see table 5.2 of the SSA report (Service 2023, p. 61)).

Resiliency is the ability of a species to withstand environmental stochasticity which is normal, year-to-year variations in environmental conditions, as well as demographic stochasticity; typically, the larger a population and the more individuals present, the more resilient the population. We assume that current threat levels influence the current population size; in other words, threats acting negatively on a population can reduce the overall size of the population, which can then result in a lower ability to withstand environmental and/or demographic stochasticity. Population size is typically used as a reliable indicator of overall resiliency. Due to the cryptic nature of Caribbean skinks and lack of research and survey data, demographic data (
i.e.,
presence/absence, abundance, population trends, population structure) are lacking in most locations. Therefore, the resiliency of the populations relies on habitat metrics such as level of habitat protection, nonnative predator pressure, and risk from storm surge.

Resiliency scores were generated by combining scores for three habitat metrics (Protection, Nonnative Predators, Storm Surge Risk). Each island was assigned a level of habitat protection based on ownership (public/private) and percentage area protected, which represents development risk, and the size of the island. Protected area percentages were assessed using the Protected Areas Database (PAD-US), the Puerto Rico Protected Areas Database, and the World Database for Protected Areas (WDPA) (UNEP-WCMC 2024, unpaginated; USGS 2022, unpaginated; Caribbean Landscape Conservation Cooperative 2016, unpaginated).

The presence of nonnative predators is an important influence on Caribbean skinks, especially when islands are small. Mongooses are known to be especially harmful to small reptiles, particularly in island habitats. The larger the island, the more complex the ecosystem due to a larger diversity of habitats, which can provide multiple patch areas and refugia, more diverse prey items for nonnative predators, and potentially a larger population of skinks (Simberloff 1974, entire; Kohn and Walsh 1994, entire). It is difficult to know when an island is “large enough” so that skinks can persist alongside the presence of nonnative predators, particularly mongooses. The smaller the island, the greater the impact of nonnative predators, including rats. We scored the level of predator pressure for each island based on the type of nonnative predator present and the size of the island. Islands smaller than 15 ha were considered likely extirpated due to a higher risk of predator dispersal.

Finally, we determined the potential impact of storm surges on skink populations. Storm surge heights were

estimated using the sea, lake, and overland surges from hurricanes (SLOSH) model used by the National Weather Service (Jelesnianski et al. 1992, entire). All simulated hurricanes had a forward speed of 15 miles per hour (the closest simulation option to the average hurricane speed of 10.8 miles per hour at 15-20 degrees north latitude; NOAA 2014, unpaginated) in a northwesterly direction, the primary direction of hurricane movement in the skinks' range. The SLOSH model predicts average storm surge heights for multiple trajectories of a hurricane of the same strength, speed, direction, and tide to account for uncertainty in the path of any one storm. To determine potential maximum impact for storm surge on each island, we simulated Category 5 hurricanes at mean tide level. For each simulated storm surge, we calculated the percent of each island or cay that lies below that elevation and would thus be inundated (or potentially flooded in cases where lower elevation areas are inland and surrounded by higher elevation areas) (see appendix A of the SSA report (Service 2023, pp. 141-145)). Note that scoring for the island of Puerto Rico is considered to be “no effect” because the skink populations on Puerto Rico are inland at high elevations and therefore not prone to the same effect from storm surges as other islands (and therefore skink populations) in the Caribbean.

The best available information for each population was gathered from the literature, data sources, and species experts. Each metric was weighed equally. Ultimately, resiliency classifications relied on habitat conditions, as affected by threats. For each metric, populations were assigned a score of −1, 0, or 1, as described below in table 1.

Table 1—Scoring of Habitat Factors To Determine Population Resiliency of Eight Caribbean Skink Species

Score
Habitat metrics
Habitat protection
Nonnative predator pressure
Storm surge risk

−1
Low
High
High: >25% inundated from category 5 hurricane.

0
Moderate
Low
Low: <25% inundated from category 5 hurricane.

1
High
No impact
No effect for main island Puerto Rico.

The scores for all habitat metrics were summed, and final relative population resiliency categories were assigned to each population (except those that are likely extirpated). The range of final scores was evenly divided into the four possible categories: High, Moderate, Low, and Likely Extirpated. Likely extirpated means that all the habitat factors are unfavorable for skink viability and the population is/would be likely extirpated. A low score means that multiple resiliency factors are not favorable for skink viability. Moderate or high scores indicate that multiple habitat factors are conducive to skink population viability on a given island.

Redundancy reduces the species' extinction risk if a portion of the species' range is negatively affected by a natural or anthropogenic catastrophic disturbance. For a Caribbean skink species to withstand catastrophic events such as hurricanes or the introduction of nonnative predators, it needs to have multiple, sufficiently resilient populations across its range. We used the Bayesian probability to determine likelihood of existence for each of the islands with historical or current populations to assess redundancy for each species. As described above, the status of the species on each of the islands (extant, likely extirpated, unknown) allowed the assessment of redundancy for each species.

Most of the Caribbean skink species exhibit limited distribution (except Puerto Rican skink) and relative geographic rarity (see appendix E of the SSA report (Service 2023, pp. 174-196)). Despite these circumstances, they appear to use a wide variety of habitat and structure across islands. They also appear moderately tolerant of human infrastructure and disturbance (
e.g.,
removal of unexploded ordnance (Puente-Rolón and Vega-Castillo 2019, p. 12)), with the exceptions of introduced nonnative predators and direct loss of habitat. There also appear to be no known restrictions to movement throughout the year.

In some cases, genetic representation is limited to a single or very few small islands, while others are represented by multiple populations on large islands and scattered outlying cays; thus, the catastrophic loss of a single island might have substantially different effects on genetic and geographic representation depending on the species. For instance, the Puerto Rican skink has multiple populations, some on a single large island and at least one on a smaller island; therefore, risk associated with catastrophic events (
e.g.,
particularly strong hurricanes and associated storm surge) would likely be distributed across more populations and complete loss of genetic diversity is less likely. However, loss of some populations could reduce genetic diversity of this species.

The Mona skink is distributed on a single large island with both higher elevation and lower elevation sites closer to the coast, while other species, such as Culebra skink, Lesser Virgin Islands skink, and Virgin Islands bronze skink, have populations on several small, low-elevation islands. In species where few, small islands contain all known genetic diversity or where a substantial proportion of sites are located on small islands, risk of losing existing representation and redundancy is likely higher. For instance, catastrophic events (
e.g.,
particularly strong hurricanes, storm surge, and overwash) could eliminate a much higher percentage of the existing genetic diversity within a species if localized skink populations are lost or are represented by only a single location on a small cay or if sea level rise acts with storm surge to remove several small islands over time. Such events could reduce species-level adaptive potential, limiting future ability to respond to changing environmental conditions (Service 2021, pp. 4-5). In addition, many of the traits are still unknown at this time for these species (
e.g.,
population size, competitive ability, site fidelity, age structure, recruitment rate, etc. (Thurman et al. 2020, entire)). Therefore, at present we have an incomplete picture of adaptive capacity for each of the species, and additional knowledge about these traits could further refine our understanding of representation.

Future Conditions Methods

The primary threats to Caribbean skinks in the future are: (1) habitat destruction and modification, (2) nonnative predators, and (3) climate change, specifically SLR, and the increases in intensity, frequency, and duration of hurricane activity. Due to a lack of survey effort in many locations and the cryptic nature of these species,

we assessed the future condition of the habitat quality on islands that have current or historical documentation of skink occurrences. We predicted resiliency at three future time points: 2050, 2070, and 2100. We considered the same metrics as current condition (habitat protection, predator pressure, risk from storm surge) as well as predicted SLR for each scenario.

Table 2—Scores of Habitat Metrics To Determine Future Resiliency of Eight Caribbean Skink Species

Score
Habitat metrics
Habitat protection
Nonnative predator pressure
Sea level rise (SLR)
Storm surge

−1
Low
High (extirpation likely on islands <15 ha)
High: >25% inundated from SLR or SLR + storm surge
High: >25% inundated from SLR + storm surge.

0
Moderate
Low
Moderate or Low: <25% inundated from SLR or SLR + storm surge
Moderate or Low: >10% but <25% inundated from SLR + storm surge.

1
High
No impact
No effect (Puerto Rico main island only).

For each influence on future resiliency of each Caribbean skink species (extant populations only), we scored each habitat factor (table 2), as previously described for current condition, and calculated final scores to determine the future resiliency of each population, under four possible scenarios (table 3).

Table 3—Future Scenarios To Determine the Resiliency of Populations of Eight Caribbean Skink Species

Scenario
Habitat protection
Nonnative predator pressure
Sea level rise (SLR) + storm surge risk

1A
same as current
same as current

Intermediate SLR + Cat3 * (2050).
Intermediate SLR + Cat5 * (2070 & 2100).

1B
same as current
increased pressure

Intermediate SLR + Cat3 (2050).
Intermediate SLR + Cat5 (2070 & 2100).

2A
same as current
same as current
High SLR + Cat5.

2B
same as current
increased pressure
High SLR + Cat5.

* Cat3 = Category 3 hurricane; Cat5 = Category 5 hurricane.

Scenario 1A

Under scenario 1A, conditions continue along their current trajectory. The risk of human development (measured here as level of habitat protection) remains the same as current, and populations that are currently impacted by the associated stressors from development remain negatively impacted by these threats. Under this scenario, we calculated impacts under the Intermediate SLR scenario as well as the additional storm surge risk from a Category 3 hurricane (2050 only) and Category 5 hurricane (2070 and 2100), which are expected to represent a higher proportion of hurricanes in the Caribbean into the future (Service 2023, pp. 52-55).

Scenario 1B

Under Scenario 1B, there is an increase in predator pressure on islands where nonnative predators do not currently occur. Impacts to small islands not currently impacted by nonnative predators include the theoretical introduction of nonnative mammalian predators, most likely rats, which can have a profound negative effect on skinks on smaller islands/cays. Because larger islands will continue to have nonnative predators, the risk will remain unchanged on those islands. The risk of human development (
i.e.,
level of habitat protection) remains the same as current because we do not have data to inform this metric in the future (note, this metric is held constant for all future scenarios). Under this scenario, we calculated impacts under the Intermediate SLR scenario as well as the additional storm surge risk from a Category 3 hurricane (2050 only) and Category 5 (2070 and 2100), which are expected represent a higher proportion of hurricanes in the Caribbean into the future.

Scenario 2A

Under Scenario 2A, habitat protection and nonnative predator risk remain status quo, and SLR and storm surge calculations are based on the High SLR scenario and the storm surge risk from Category 5 hurricanes for all time iterations.

Scenario 2B

Under scenario 2B, impacts of nonnative predators, SLR, and storm surge worsen. Impacts to small islands not currently impacted by nonnative predators include the theoretical introduction of nonnative mammalian predators. Because larger islands will continue to have nonnative predators, the risk will remain unchanged on those islands, but we expect the impacts to continue to increase since eradication is not feasible and exacerbated as human population sizes increase; therefore, this scenario includes the lowering of habitat protection category by one level. For this scenario we calculated impacts using the High SLR scenario as well as the additional storm surge risk from Category 5 hurricanes.

Puerto Rican Skink

Here, we present both current and future condition analyses results for the Puerto Rican skink. There are currently four known extant Puerto Rican skink populations on the island of Puerto Rico and one on the island of Desecheo. Historical records indicate that Puerto Rican skinks likely occurred on Icacos (1932) and Vieques (1980; figure 2.16; Hedges and Conn 2012, p. 186), and on the main island of Puerto Rico skinks were historically collected in and around San Juan (in 1879, 1880) and Bayamón (in 1919, 1931); the southern coastal areas including Ensenada (in 1915, 1919), North Descalabrado (in 1967), and Cerro del Muerto (in 1980); Cape San Juan (in 1931) which is in extreme northeastern Puerto Rico; and Barrio Coto in the municipality of

Isabela (in 1966), which is near Quebradillas (Hedges and Conn 2012, p. 186). Skink populations in San Juan and Cape San Juan are considered historical and are designated as likely extirpated in our analyses. Three skink specimens, one from Culebra, another from Cayo Norte, and one from Cayo Luis Peña in Culebra, were also assigned to the Puerto Rican skink species; however, there is no genetic information for these three specimens to confirm if Puerto Rican skinks are sympatric with Culebra skinks. Unlike other island populations of skinks, which are much smaller than those on the main island of Puerto Rico, we treat each skink population on the main island of Puerto Rico separately regarding amount of predator pressure and level of protection.

Habitat Protection

For level of protection, we describe the total percentage protected and indicate the percentage that includes the
Zona de Conservación del Carso
(Karst Conservation Zone) due to differences in protection levels as compared to other protected areas. This zone includes both public and privately owned lands, and conservation within this zone cannot be considered conclusive since permits for certain activities within this zone are subject to PRDNER evaluation and there is uncertainty if activities will be allowed or not.

Most of the information for the Quebradillas population is from near and in the Guajataca Commonwealth Forest, which is a subtropical moist forest occurring within the karst landscape in the northwestern municipality of Isabela, Puerto Rico. The Quebradillas population encompasses almost ~42,000 ac (17,000 ha) of predicted habitat, with 73 percent of that area with varied protection designations (67 percent Karst Conservation Zone, 6 percent other protected areas (Service 2023, pp. 74-76)). The high habitat protection in this area is considered to provide a lower development risk, primarily due to restricted development within the Karst Conservation Zone.

The southwest population overlaps with several municipalities where skinks have been documented, particularly within and around the southern portions of the Maricao Commonwealth Forest (San Germán and Sabana Grande within humid subtropical forests; Rivera et al. 2023, p. 10). This large area of predicted habitat (92,986 ac (37,630 ha)) has 22 percent (6 percent within Karst Conservation Zone, 16 percent other protected areas) of that area being protected.

The third population occurs in south central Puerto Rico in the municipality of Ponce. Of the 6,155 ac (2,491 ha) of predicted habitat in the area, very little is protected (approximately 1 percent); therefore, development risk is high.

In 2022, a skink was collected inside a garage in north central Puerto Rico in the municipality of Florida, an area where skinks had not been detected in the past but includes 19,714 ac (7,978 ha) of predicted skink habitat. A large percentage of this potential habitat is currently protected (88 percent). Of the area protected, 78 percent is within the Karst Conservation Zone and 10 percent is within other protected areas.

Outside of the main island, the only other population known to be extant is on the island of Desecheo off the west coast of Puerto Rico. During surveys in 2010, 2012, and 2016, researchers observed skinks that are presumed to be Puerto Rican skinks (Wolf et al. 2010, p. 5; Herrera-Giraldo and Bermudez 2010, p. 22; Figuerola 2023, pers. comm.). The entire island is a National Wildlife Refuge (NWR) with no development risk.

Predator Pressure

Because the main island of Puerto Rico is occupied by nonnative predators including mongooses, rats, cats, etc., the influence of predator pressure on population resiliency is always present and therefore considered high risk to skinks in all main island populations. Nonnative predators have been eradicated from Desecheo; therefore, there is currently no impact from predator pressure for this population.

Storm Surge Risk

The populations on the main island of Puerto Rico occur inland and are not influenced by storm surge. In addition, Desecheo is an island with high elevation; therefore, skink populations there are not impacted by the effects of storm surge.

Current Condition Summary

Currently, five of nine (56 percent) known populations are extant, while four (44 percent) are considered likely extirpated (table 4). One population (Desecheo) is in high resiliency condition, and two (Quebradillas and Florida) are in moderate resiliency condition, and these populations are distributed across the northern part of the species' range on Puerto Rico and Desecheo Island; the remaining two populations (Southwest and Ponce) have low resiliency (table 4). Habitat for all populations is generally located at elevations that are not at risk of storm surge or sea level rise. Development is a risk to all populations. Because the main island of Puerto Rico is occupied by nonnative predators including mongoose, rats, cats, and dogs, the influence of predator pressure on population resiliency is always present and therefore considered high risk to skinks. In addition, all current populations are geographically isolated at considerable distance from one another; therefore, it will be difficult for a high or moderate condition population to supplement or rescue another population affected by threats. Thus, current redundancy is low for the Puerto Rican skink.

Given the reduction in historical range, representation has also been reduced from historical condition. However, current populations exist in multiple locations in several different habitat types across Puerto Rico and on Desecheo Island. Based on the genetic analysis, the populations on Puerto Rico may range from small to large effective population sizes with potential for admixture, although there is some evidence of inbreeding within the Florida population (Rivera et al. 2023, p. 20). This apparent genetic diversity across Puerto Rican skink populations contributes to the species' overall adaptive capacity, giving the species the potential to adapt when faced with changes in its current or future environment.

Table 4—Puerto Rican Skink Current Resiliency Summary
[Numbers in parentheses are metric scores (see table 1), summed to provide overall resiliency. NA = not applicable, as likely extirpated populations do not have resiliency.]

Population
Habitat protection
Predator pressure
Risk from storm surge
Status
Resiliency

Icacos
High (1)
High (−1)
High (−1)
Likely extirpated
NA.

Desecheo
High (1)
No Impact (1)
Low (0)
Extant
High (2).

Vieques
High (1)
High (−1)
Low (0)
Likely extirpated
NA.

Main Island, PR

San Juan
Low (−1)
High (−1)
Low (0)
Likely extirpated
NA.

Cape San Juan
Moderate (0)
High (−1)
Low (0)
Likely extirpated
NA.

Quebradillas
High (1)
High (−1)
No effect (1)
Extant
Moderate (1).

Southwest
Low (−1)
High (−1)
No effect (1)
Extant
Low (−1).

Ponce
Low (−1)
High (−1)
No effect (1)
Extant
Low (−1).

Florida
High (1)
High (−1)
No effect (1)
Extant
Moderate (1).

As part of the SSA report, we also developed future-condition scenarios to capture the range of uncertainties regarding future threats and the projected responses by the Puerto Rican skink. Our scenarios assumed nonnative predators and further fragmentation from development are the main risks to populations on Puerto Rico and the only future threat to the population on Desecheo would be if predators are introduced, which would cause reduced resiliency (note: it is highly unlikely that mongooses would ever be introduced). Because we determined that the current condition of the Puerto Rican skink is consistent with the Act's definition of an endangered species (see
Determination of Status—Puerto Rican Skink,
below), we are not presenting the results of the future scenarios in this proposed rule. Please refer to the SSA report (Service 2023, pp. 79-82) for the full analysis of future scenarios.

Mona Skink

The Mona skink is historically and currently known only from Mona Island, a 13,838-ac (5,600-ha) island off the west coast of Puerto Rico. The entire island is a designated nature preserve protected and managed by the PRDNER. The Mona skink has been consistently detected on the island over time, with the earliest known detection in 1894 to more recent detections in 2021. The species is readily observed on Mona Island, indicating this singular population has maintained a level of resiliency to withstand stochastic events over time. Although the species is limited to one island, there are multiple, interconnected habitat patches occupied across the island (Rivera et al. 2023, p. 12). The species occupies interior areas of the island, which are not subject to storm surge or sea level rise. These habitat patches that do not experience SLR and storm surge threats likely ensure that the species is less susceptible to catastrophic events; however, the species is still vulnerable to other unknown threats given that its range is limited to one island. The one population on Mona Island houses all known genetic diversity for the species; however, genetic evidence is insufficient to determine the level of genetic diversity.

The primary threat driving species' viability is nonnative predators. Mona Island is currently occupied by nonnative predators (cats and rats). There are no mongooses or dog predators on the island. Given the larger size of the island and the fact that mongooses are not present, predator pressure was assessed as low for the species. Low does not mean there is no predator pressure but a lower level of predator pressure from cats and rats. Mona Island has a maximum elevation of over 296 feet (ft) (90 meters (m)) and, therefore, most of the island is not susceptible to impacts from storm surge or sea level rise like other low-lying islands. Mona Island has high habitat protection given it is protected and managed by PRDNER, and therefore there are no current impacts from development pressure.

The current resiliency of the one Mona skink population is moderate (table 5). Though the species is known only from Mona Island and is considered a single population, habitat patches are occupied across the island, and the species occupies interior as well as coastal areas of the island. Although the species is impacted by some threats across the range, the Mona skink exhibits sufficient resiliency, redundancy, and representation to support the species' viability.

Table 5—Mona Skink Current Resiliency Summary
[Numbers in parentheses are metric scores (see table 1), summed to provide overall resiliency.]

Population
Habitat protection
Predator pressure
Risk from storm surge
Status
Resiliency

Mona Island
High (1)
Low (0)
Low (0)
Extant
Moderate (1)

In considering future threats to the species, nonnative predators are the primary driver to the species' viability in the future. Given the larger size of the island, and that mongooses are not likely to be introduced, predator pressure was assessed as low in the future for the species. Nonnative predator introductions would be expected to reduce skink numbers on the island, but there are a diversity of habitats and patches, and it is a large island; therefore, predation risk is not likely to eliminate the known population, nor do we expect it to reduce to low resiliency condition in the future. Impacts from climate change in the future were also assessed as low given the higher elevation of the island. Further, impacts of development pressure to the species are low as Mona Island has high habitat protection given it is protected and managed by PRDNER.

Table 6—Mona Skink Future Resiliency Summary for Four Future Scenarios Under Three Time Steps
[M = moderate]

Current
Status
Resiliency
2050
1A
1B
2A
2B
2070
1A
1B
2A
2B
2100
1A
1B
2A
2B

Extant
M
M
M
M
M
M
M
M
M
M
M
M
M

The projected future resiliency of skinks on Mona Island is assessed as moderate (table 6), given the future level of threats to the species. The future range of the Mona skink is limited to one island; however, it is still expected to have moderate resiliency to withstand stochastic events. Although the species is impacted by several threats across the range, the Mona skink exhibits sufficient resiliency, redundancy, and representation to support the species' future viability.

Culebra Skink

The Culebra skink currently occupies five islands including Culebra and several of the small cays surrounding Culebra Island. Culebra skinks were historically found on Isla Culebrita, the largest cay near Culebra, but they have not been seen there since 1936 likely because it is a small to medium sized island with nonnative predators. Observations on the cays surrounding Culebra Island, including Cayo Agua, Cayo Botella, Cayo Lobito, and Cayo Yerba are recent (since 2017).

The small cays currently occupied by skinks are very small (<10 ac (<4 ha)), are not currently occupied by any nonnative predators, and are protected from development. Much of the land on each cay is low elevation (
i.e.,
less than 33 ft (10 m)) making them susceptible to storm surge, with projected Category 3 storms at 5 ft (1.52 m) and Category 5 storms at 6 ft (1.83 m) (see table 8.3 and appendix A of the SSA report; Service 2023, pp. 92, 142). Culebra Island is inhabited by people, and there is development on parts of the island, except in areas that are protected, primarily within the Culebra NWR. Although mongooses have not been observed, other nonnative predators including cats and rats occur there. Culebra Island has a higher average elevation (~646 ft (197 m)) than the smaller cays and is less susceptible to storm surge risk currently.

Each of the small cays currently occupied by Culebra skinks is relatively similar; each cay is protected and not currently occupied by nonnative mammalian predators. However, because they each have low elevations and are small in size, the risk of impacts from storm surge is high, and therefore they currently have moderate resiliency (table 7). Even though the Culebra skink on Culebra Island is less impacted by storm surge and has large tracts of protected areas, it has moderate current resiliency because several nonnative predators occupy the island. In addition, skinks occur partially on unprotected lands, which are vulnerable to development.

Table 7—Culebra Skink Current Resiliency Summary
[Numbers in parentheses are metric scores (see table 1), summed to provide overall resiliency. NA = not applicable, as likely extirpated populations do not have resiliency.]

Population

Habitat
protection

Predator pressure
Risk from storm surge
Status
Resiliency

Isla Culebrita
High (1)
Low (0)
Low (1)
Likely extirpated
NA

Cayo Botella
High (1)
No impact (1)
High (−1)
Extant
Moderate (1)

Cayo Agua
High (1)
No impact (1)
High (−1)
Extant
Moderate (1)

Cayo Lobito
High (1)
No impact (1)
High (−1)
Extant
Moderate (1)

Cayo Yerba
High (1)
No impact (1)
High (−1)
Extant
Moderate (1)

Culebra
Moderate (0)
Low (0)
Low (0)
Extant
Moderate (0)

Currently, the Culebra skink has multiple populations in moderate resiliency condition across its known range (table 7). The number and distribution of these sufficiently resilient populations enable the species to withstand both stochastic and catastrophic events. The range is not large, and many of the islands are small, but the species currently has substantial genetic representation in the form of separate islands.

Table 8—Culebra Skink Current and Future Resiliency Summary
[NA = not applicable, as likely extirpated populations do not have resiliency; M = moderate; X = extirpated.]

Population
Current
Status
Resiliency
2050
1A
1B
2A
2B
2070
1A
1B
2A
2B
2100
1A
1B
2A
2B

Isla Culebrita
Likely extirpated
NA

Cayo Botella
Extant
Moderate
M
X
M
X
M
X
X
X
X
X
X
X

Cayo Agua
Extant
Moderate
M
X
M
X
M
X
M
X
M
X
X
X

Cayo Lobito
Extant
Moderate
M
X
M
X
M
X
M
X
M
X
M
X

Cayo Yerba
Extant
Moderate
M
X
M
X
M
X
M
X
M
X
X
X

Culebra
Extant
Moderate
M
Low
M
Low
M
Low
M
Low
M
Low
M
Low

By 2050, resiliency of each of the populations will change only if predator pressure is increased (see “B” scenarios in table 8). Since most of the populations are on small cays, the addition of a predator will almost certainly mean the extirpation of skinks within a short time. Results are similar for 2070 except Cayo Botella will

become too small to support a population of skinks under the High SLR scenario (Scenario 2A, table 8). By 2100, nearly all the small cays (except for Cayo Lobito) will be classified as extirpated under the High SLR scenario (Scenario 2A) and skinks on Cayo Botella will likely be extirpated under both Intermediate and High SLR scenarios (table 8). The main risk on the main island of Culebra is the increased predator pressure and continued habitat modification. The addition of any predator to the small cays would likely lead to the skinks being quickly extirpated.

Future redundancy and representation of Culebra skink is expected to be reduced by 2100 under most scenarios, ultimately with the loss of smaller cays due to a combination of predator introduction and SLR/storm surge. Only two populations are expected to remain (Culebra and possibly Cayo Lobito) by 2100 if predators are not introduced to the small cays; therefore, redundancy at 2100 would be limited. There is evidence of genetic clustering (
i.e.,
grouping of similar genes) between populations on Culebra, but the actual genetic structure of skinks on Culebra is still largely unknown (Rivera et al. 2023, p. 15). Culebra has some diverse habitats, and skinks have been seen in both the coast and upland forests. Coastal areas will likely be impacted by sea level rise. Therefore, representation is expected to be substantially reduced across the range by 2100 under three of four future scenarios.

Greater Virgin Islands Skink

The Greater Virgin Islands skink is believed to be historically distributed in the USVI on St. John and St. Thomas (Hedges and Conn 2012, p. 210). It is possible that the Greater Virgin Islands skink occurred in the BVI as well. The species likely had patchy distribution across its range, and its small size, cryptic coloration, and secretive behavior could account for its lack of detection. If observed, it could be misidentified as the sympatric Lesser Virgin Islands skink or Virgin Islands bronze skink, but lack of observations of any skinks on St. John or St. Thomas make misidentification less probable.

The Greater Virgin Islands skink has not been seen in nearly 150 years since the last specimen was cataloged in 1877, despite considerable herpetological survey work through the Virgin Islands (Hedges and Conn 2012, p. 210). There are six known museum specimens, collected in 1779-1799, 1834, 1845-1846, and 1877 (Hedges and Conn 2012, p. 207). Because the species has long been believed to be extirpated from the main islands of St. John and St. Thomas, not many targeted surveys have been undertaken to look for skinks on either island. From 1986 to 2023, qualified researchers and wildlife agency staff invested considerable efforts in looking for other herpetofauna that would almost certainly document opportunistic encounters of any herp species, and no known documentation of skinks exist (Service 2023, pp. 150-151). Herp survey efforts on St. Thomas do not appear to be as extensive as those on St. John, but optimal habitat on St. Thomas is known to be fragmented by extensive human development (Platenberg and Harvey 2010, p. 548), and the consensus from the herpetology community is that there are no known skinks on the island of St. Thomas. Given what is known about the life history and habitat associations of
Spondylurus
skinks, it is reasonable to assume that skinks would have been detected given the extent of survey efforts in optimal habitats on both islands of St. Thomas and St. John (see chapter 9 and appendix B-I of the SSA report (Service 2023, pp. 100, 146-152)).

Skinks that once occurred on the islands of St. Thomas and St. John faced a primary threat from the introduced mongoose, a predator that has been implicated in the extinction of the Greater Virgin Islands skink (Hedges and Conn 2012, p. 210; Hedges 2013, p. 1). The invasive predator was introduced as a biological control of rats in sugar cane fields in the late nineteenth century, immediately resulting in a mass extinction of skinks and other reptiles (Hedges and Conn 2012, p. 4). The ground-dwelling and diurnal habits of skinks make them particularly susceptible to mongoose predation.

Based on the best scientific and commercial information available, it is highly unlikely that an individual of Greater Virgin Islands skink could be extant but undetected; therefore, we presume that the species is likely extinct.

Lesser Virgin Islands Skink

Lesser Virgin Islands skink was historically known to occur on 15 islands within the USVI and BVI. The populations on three historically occupied islands, making up approximately 43 percent of the species' historical range, are considered likely extirpated, including St. Thomas, the largest island in the USVI, and two islands in BVI (Necker Island and Great Camanoe Island). The status of seven populations (Capella Island, Buck Island (St. Thomas), Little Thatch Island, Fallen Jerusalem, Salt Island, Round Rock Island, and Ginger Island) are currently unknown, primarily because recent surveys have not been conducted, and very little information is known about these islands. However, there is a high likelihood that skinks could be extirpated on these islands given the nonnative predator threat on surrounding islands and the short distance of the seven islands to those with known predator presence. Given the potential for these threats and likely extirpation of skinks, we assumed that these seven unknown populations do not contribute to the resiliency, redundancy, and representation for the species and thus were not considered as contributing to overall species viability.

Table 9—Lesser Virgin Islands Skink Current Resiliency Summary
[Numbers in parentheses are metric scores (see table 1), summed to provide overall resiliency. NA = not applicable, as likely extirpated and unknown populations do not have resiliency.]

Population

Habitat
protection

Predator pressure
Risk from storm surge
Status
Resiliency

USVI

Capella Island
High (1)
No impact (1)
Low (0)
Unknown
NA

Buck Island
High (1)
No impact (1)
Low (0)
Unknown
NA

Hans Lollik
Low (−1)
Low (0)
Low (0)
Extant
Low (−1)

St. Thomas
Moderate (0)
High (−1)
Low (0)
Likely extirpated
NA

BVI

Little Thatch Island
Low (−1)
Low (0)
Low (0)
Unknown
NA

Fallen Jerusalem
High (1)
Unknown
Low (0)
Unknown
NA

Salt Island
Moderate (0)
Low (0)
Low (0)
Unknown
NA

Round Rock Island
High (1)
Unknown
High (−1)
Unknown
NA

Ginger Island
Low (−1)
Unknown
Low (0)
Unknown
NA

Guana Island
Low (−1)
Low (0)
Low (0)
Extant
Low (−1)

Necker Island
Low (−1)
Low (0)
Low (0)
Likely extirpated
NA

Great Camanoe Island
Moderate (0)
Low (0)
Low (0)
Likely extirpated
NA

Mosquito Island
Low (−1)
No impact (1)
Low (0)
Extant
Moderate (0)

Virgin Gorda
Moderate (0)
High (−1)
Low (0)
Extant
Low (−1)

Tortola
Moderate (0)
High (−1)
Low (0)
Extant
Low (−1)

Currently, the species is considered extant on 5 of the 15 islands: 1 in USVI (Hans Lollik) and 4 in BVI (Guana, Mosquito, Virgin Gorda, and Tortola) (table 9). Of the five, four have low resiliency, and one has moderate resiliency. Hans Lollik, the one extant population in the USVI, currently has low resiliency due to lack of habitat protection (privately owned) and predator pressure (rats present). In the BVI, one population is currently moderate, and three are low resiliency. There are mixed levels of habitat protection for the islands in the BVI; thus, development pressure is a risk to the species. In addition, each island has variable impacts from nonnative predators, and the two larger islands (Tortola and Virgin Gorda) have mongooses present. All islands have low impacts from storm surge due to the average height of these islands all being above 60 m (197 ft).

Together, the extirpated and low-resiliency populations represent 94 percent of the range of the Lesser Virgin Islands skink. Given the reduction in historical range, the species' redundancy and representation (adaptive capacity) have been greatly reduced from historical condition. Current redundancy, or distribution of populations with sufficient resiliency to withstand catastrophic events, is very low for this species as there is only one moderate-resiliency population remaining. Given the limited range, any catastrophic event would likely negatively impact all existing populations, thus the species is unlikely to withstand catastrophic events.

As part of the SSA report, we also developed future-condition scenarios to capture the range of uncertainties regarding future threats and the projected responses by the Lesser Virgin Islands skink. Our scenarios assumed nonnative predators are the main risk to populations which would cause reduced resiliency (note: it is highly unlikely that mongooses would ever be introduced). Because we determined that the current condition of the Lesser Virgin Islands skink is consistent with the Act's definition of an endangered species (see
Determination of Status—Lesser Virgin Islands Skink,
below), we are not presenting the results of the future scenarios in this proposed rule. Please refer to the SSA report (Service 2023, pp. 108-117) for the full analysis of future scenarios.

Virgin Islands Bronze Skink

Virgin Islands bronze skink was historically known to occur on nine islands within the USVI and BVI. Four populations, making up approximately 96 percent of the species' historical range, are considered likely extirpated, including St. Thomas, the largest island in the USVI, and three islands in BVI (Little Tobago Island, Norman Island, and Peter Island). Currently, three of the nine islands are extant, all within the USVI (Buck Island, Turtledove Cay, and Water Island); there are no known extant populations occurring in BVI. The status of two populations (Capella Island and Salt Island) are currently unknown, primarily because recent surveys have not been conducted and very little information is known about these islands. Thus, we assumed that these two populations do not contribute to the resiliency, redundancy, and representation for the species and thus were not considered as contributing to overall species viability.

Table 10—Virgin Islands Bronze Skink Current Resiliency Summary
[Numbers in parentheses are metric scores (see table 1), summed to provide overall resiliency. NA = not applicable, as likely extirpated and unknown populations do not have resiliency.]

Population
Habitat protection
Predator pressure
Risk from storm surge
Status
Resiliency

USVI

Buck Island
High (1)
No impact (1)
Low (0)
Extant
High (2)

Capella Island
High (1)
No impact (1)
Low (0)
Unknown
NA

Turtledove Cay
High (1)
No impact (1)
Low (0)
Extant
High (2)

Water Island
Low (−1)
Low (0)
Low (0)
Extant
Low (−1)

St. Thomas
High (1)
High (−1)
Low (0)
Likely extirpated
NA

BVI

Little Tobago Island
High (1)
Low (0)
Low (0)
Likely extirpated
NA

Salt Island
Moderate (0)
Low (0)
Low (0)
Unknown
NA

Norman Island
Low (−1)
Low (0)
Low (0)
Likely extirpated
NA

Peter Island
Low (−1)
Low (0)
Low (0)
Likely extirpated
NA

Of the three extant populations, two were assessed to have high resiliency while one was assessed to have low resiliency (table 10).Water Island, the largest island (489 ac (198 ha)) with an extant population, is currently occupied by nonnative predators (rats) and privately owned, and therefore has low resiliency. Buck Island and Turtledove Cay have high resiliency due to high levels of habitat protection and no current predator pressure, as nonnative predators were eradicated previously, and the islands' elevations are not at risk from storm surge. Despite having two populations with high resiliency, the Virgin Islands bronze skink is vulnerable to catastrophic events such as the introduction of nonnative predators, primarily due to the extremely small size of the remaining extant islands (
i.e.,
Buck Island and Turtledove Cay are 22 and 32 ac (9 and 13 ha) in size, respectively). Representation (and adaptive capacity) has been greatly reduced due to the loss of historical range and remaining islands making up 4 percent of the species' current range.

As part of the SSA report, we also developed future-condition scenarios to capture the range of uncertainties regarding future threats and the projected responses by the Virgin Islands bronze skink. Our scenarios assumed nonnative predators and SLR are the main risks to populations in the future, which would cause reduced resiliency and eventual extirpation (note: it is highly unlikely that mongooses would ever be introduced). Because we determined that the current condition of the Virgin Islands bronze skink is consistent with the Act's definition of an endangered species (see
Determination of Status—Virgin Islands Bronze Skink,
below), we are not presenting the results of the future scenarios in this proposed rule. Please refer to the SSA report (Service 2023, pp. 122-129) for the full analysis of future scenarios.

Greater St. Croix Skink

The Greater St. Croix skink has been recorded from St. Croix and its satellite island Green Cay, both in the USVI; this is also presumed to be the provenance of several historical specimens with the locality data “West Indies,” suggesting that the skink was endemic to this large island and its satellite (Hedges and Conn 2012, p. 173). No more specific locality data are available, and the species was last recorded from St. Croix in the late 19th century, but this species has a well-documented collection history, and it is consequently “without dispute” that the species historically occurred on the island (Hedges and Conn 2012, p. 174).

Because the species has long been believed to be extirpated from St. Croix, not many targeted surveys to look for skinks on the island have occurred. Qualified researchers and wildlife agency staff have made several efforts to look for other herpetofauna on both St. Croix and Green Cay that would almost certainly document opportunistic encounters of any herp species, and since 2000, no known documentation of skinks exists (see appendix B-II of SSA report (Service 2023, pp. 154-160)). Given what is known about the life history and habitat associations of
Spondylurus
skinks, it is reasonable to assume that skinks would have been detected given the extent of survey efforts in optimal habitats on St. Croix and Green Cay.

Skinks that once occurred on St. Croix faced a primary threat from the introduced mongoose, a predator that has been implicated in the extinction of the Greater St. Croix skink (Hedges and Conn 2012, p. 174; Hedges 2013, p. 4). The invasive predator was introduced as a biological control of rats in sugar cane fields in the late nineteenth century, immediately resulting in a mass extinction of skinks and other reptiles (Hedges and Conn 2012, p. 4). The ground-dwelling and diurnal habits of skinks have made them particularly susceptible to mongoose predation.

Based on the best scientific and commercial information available, it is highly unlikely that an individual of Greater St. Croix skink could be extant but undetected; therefore, we presume that the species is likely extinct.

Lesser St. Croix Skink

The Lesser St. Croix skink is believed to be endemic to the large island of St. Croix in the USVI, which has an area of 230 km
2
(Hedges and Conn 2012, p. 69). The only known specimen from 1875 was reported with no precise locality data (Hedges and Conn 2012, p. 68). The introduction of mongooses to this island in the late 19th century, and the seeming disappearance of the Greater St. Croix skink at the same time, suggests that the Lesser St. Croix skink is probably now extinct (Hedges and Conn 2012, p. 69).

Because the species has long been believed to be extirpated from St. Croix, not many targeted surveys to look for skinks on the island have occurred. Qualified researchers and wildlife agency staff have made several efforts to look for other herpetofauna that would almost certainly document opportunistic encounters of any herp species (see appendix B-III of SSA report (Service 2023, pp. 162-168)). Given what is known about the life history and habitat associations of
Capitellum
skinks, it is reasonable to assume that skinks would have been detected given the extent of survey efforts in optimal habitats on St. Croix.

Skinks that once occurred on St. Croix faced threats from habitat loss and predation from the introduced mongoose, a predator that has been implicated in the extinction of the Lesser St. Croix skink (Hedges and Conn 2012, p. 69; Hedges 2013, p. 1) and other lizards. For example, the mongoose is also partly implicated for the extirpation of the endangered St. Croix ground lizard, last seen on the main island of St. Croix in 1964 (Service 1984, entire). The mongoose was introduced as a biological control of rats in sugar cane fields in the late nineteenth century, immediately resulting in a mass extinction of skinks and other reptiles (Hedges and Conn 2012, p. 4). The ground-dwelling and diurnal habits of skinks have made them particularly susceptible to predation by mongooses and cats.

Based on the best scientific and commercial information available, it is highly unlikely that an individual of Lesser St. Croix skink could be extant but undetected; therefore, we presume that the species is likely extinct.

Determination of Status for Eight Caribbean Skink Species

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 an endangered species or a threatened species. The Act defines an “endangered species” as a species in danger of extinction throughout all or a significant portion of its range and a “threatened species” as a species 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 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.

Status Throughout All of Its Range—Puerto Rican Skink

After evaluating threats to the species and assessing the cumulative effect of the threats under the Act's section 4(a)(1) factors, we assessed the status of the Puerto Rican skink to determine if it meets the Act's definition of an endangered species. The Puerto Rican skink was historically known from three island populations and six populations on the main island of Puerto Rico. Four historical populations, approximately 35 percent of the species' historical range, are considered likely extirpated, including two of the smaller islands within the range.

Of the five extant populations, one of the smaller islands, Desecheo, is currently occupied and has high resiliency based on habitat metrics, including no predators, and the island is protected as an NWR. Predators were previously present on Desecheo and success of eradication efforts was confirmed in 2017. Of note, the last detection record for the Puerto Rican skink on Desecheo Island was in 2016, although there were no surveys conducted on the island during 2021-2023 survey efforts. This population represents 0.19 percent of the extant range.

The remaining four populations occur on the main island of Puerto Rico; two populations currently have moderate resiliency, and two have low resiliency. Habitat for all populations is generally located at elevations that are not at risk of storm surge or sea level rise. Development (Factor A) is a risk to all populations. Because the main island of Puerto Rico is occupied by nonnative predators (Factor C) including mongooses, rats, cats, and dogs, the influence of predator pressure on population resiliency is always present and therefore considered high risk to skinks.

The five extant populations are geographically isolated at considerable distance from one another, and, therefore, it will be difficult for a higher resiliency population to supplement or rescue another population affected by potential catastrophic events. Together, the extirpated and low-resiliency populations represent 75 percent of the range. Given the reduction in historical range, the species' redundancy has been reduced from historical condition, and representation (and adaptive capacity) has also been reduced. The current resiliency, redundancy, and representation indicate that the magnitude and scale of threats are currently impacting the Puerto Rican skink such that it meets the Act's definition of an endangered species.Thus, after assessing the best available information, we determine that Puerto Rican skink is in danger of extinction throughout all of its range. Because the threats are currently impacting the species such that it is in danger of extinction currently throughout all of its range, it does not meet the Act's definition of a threatened species.

Status Throughout a Significant Portion of Its Range—Puerto Rican Skink

Under the Act and our implementing regulations, a species may warrant listing if it is in danger of extinction or likely to become so within the foreseeable future throughout all or a significant portion of its range. We have determined that the Puerto Rican skink 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 Puerto Rican skink 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), because that decision related to significant portion of the range analyses for species that warrant listing as threatened, not endangered, throughout all of their range.

Determination of Status—Puerto Rican Skink

Based on the best scientific and commercial data available, we determine that the Puerto Rican skink meets the Act's definition of an endangered species. Therefore, we propose to list the Puerto Rican skink as an endangered species in accordance with sections 3(6) and 4(a)(1) of the Act.

Status Throughout All of Its Range—Mona Skink

After evaluating threats to the species and assessing the cumulative effect of the threats under the section 4(a)(1) factors, we evaluated the status of the Mona skink to determine if it meets the Act's definition of an endangered species. The Mona skink is historically and currently known only from Mona Island, a 13,838-ac (5,600-ha) island off the west coast of Puerto Rico. The entire island is a designated nature preserve protected and managed by the PRDNER. The Mona skink has been consistently detected on the island over time with the earliest known detection in 1894 to more recent detections in 2021. The species continues to be observed on Mona Island, indicating that the population has maintained a level of resiliency to withstand stochastic events over time.

The primary threat driving the species' viability is nonnative predators (Factor C). Mona Island is currently occupied by nonnative predators (cats and rats) and also goats and pigs. There are no mongooses or dog predators on the island. Given the larger size of the island and that mongooses are not present, predator pressure was assessed as low for the species. Low does not mean there is no predator pressure but a lower level of predator pressure from cats and rats. Mona Island has a maximum elevation of over 296 ft (90 m) and, therefore, most of the island is not susceptible to impacts from storm surge or sea level rise (Factor E) like other low-lying islands. Mona Island has high habitat protection given it is protected and managed by PRDNER, and therefore there are no current impacts from development pressure (Factor A).

The current resiliency of the one Mona skink population is moderate. Though the species is known only from Mona Island and likely consists of a single population, there are multiple habitat patches occupied across the island and the species occupies interior as well as coastal areas of the island. Although the species is impacted by some threats across the range, the Mona skink exhibits sufficient resiliency, redundancy, and representation to support the species' viability. Overall, no current threat is acting at an extent or severity such that the species is at risk of extinction throughout all of its range. Thus, after assessing the best available information, we conclude that the Mona skink is not in danger of extinction throughout all of its range. Therefore, we proceed with determining whether the Mona skink is likely to become endangered within the foreseeable future throughout all of its range.

In considering future threats to the species, we examined habitat destruction and modification from development risk (Factor A); nonnative predators (Factor C); climate change, specifically SLR (Factor E); and increases in intensity, frequency, and duration of hurricane activity (Factor E) out to the end of the century, or 2100. For the Mona skink, nonnative predators are the primary driver to the species' viability in the future. There is a chance of introduction of additional nonnative predators from tourism, and thus increased predator pressure to the Mona skink in the future. However, ongoing and future funded eradication efforts of nonnative predators is likely to occur. Given the larger size of the

island, and that mongooses are not likely to be introduced, predator pressure was assessed as low in the future for the species. Nonnative predator introductions would be expected to reduce skink numbers on the island, but the island is large and includes a diversity of habitats and patches: therefore, predation risk is not likely to eliminate the known population, nor do we expect it to reduce to low-resiliency condition in the future. Impacts from climate change in the future were also assessed as low for similar reasons as current impacts because most of the island is not susceptible to impacts from SLR or increased hurricane activity. Further, impacts of development pressure to the species are low as Mona Island has high habitat protection given it is protected and managed by PRDNER.

The projected future resiliency of skinks on Mona Island is assessed as moderate, given the future level of threats to the species. The future range of the Mona skink is limited to one island; however, it is still expected to have moderate resiliency to withstand stochastic events. Although the species is impacted by some level of threats across the range, the Mona skink exhibits sufficient resiliency, redundancy, and representation to support the species' future viability. Overall, no projected future threat is acting at an extent or severity such that the species is at risk of extinction throughout all of its range within the foreseeable future. Thus, after assessing the best available information, we conclude that the Mona skink is not likely to become endangered within the foreseeable future throughout all of its range.

Status Throughout a Significant Portion of Its Range—Mona Skink

Under the Act and our implementing regulations, a species may warrant listing if it is in danger of extinction or likely to become so within the foreseeable future throughout all or a significant portion of its range. Having determined that the Mona skink is not in danger of extinction or likely to become so within the foreseeable future throughout all of its range, we now consider whether it may be in danger of extinction or likely to become so within the foreseeable future in a significant portion of its range—that is, whether there is any portion of the species' range for which it is true that both (1) the portion is significant; and (2) the species is in danger of extinction now or likely to become so within the foreseeable future in that portion. Depending on the case, it might be more efficient for us to address the “significance” question or the “status” question first. We can choose to address either question first. Regardless of which question we address first, if we reach a negative answer with respect to the first question that we address, we do not need to evaluate the other question for that portion of the species' range.

In undertaking this analysis for the Mona skink, we chose to address the status question first. We began by identifying portions of the range where the biological status of the species may be different from its biological status elsewhere in its range. For this purpose, we considered information pertaining to the geographic distribution of (a) individuals of the species, (b) the threats that the species faces, and (c) the resiliency condition of populations.

We evaluated the range of the Mona skink to determine if the species is in danger of extinction now or likely to become so within the foreseeable future in any portion of its range. The Mona skink is a narrow endemic that functions as a single, contiguous population and occurs on one 13,838-ac (5,600-ha) island (Mona Island). Thus, there is no biologically meaningful way to break this limited range into portions, and the threats that the species faces affect the species comparably throughout its entire range. As a result, there are no portions of the species' range where the species has a different biological status from its rangewide biological status. Therefore, we conclude that there are no portions of the species' range that warrant further consideration, and the species is not in danger of extinction or likely to become so within the foreseeable future in any significant portion of its range. This does not conflict with the courts' holdings in
Desert Survivors
v.
U.S. Department of the Interior,
321 F. Supp. 3d 1011, 1070-74 (N.D. Cal. 2018) and
Center for Biological Diversity
v.
Jewell,
248 F. Supp. 3d. 946, 959 (D. Ariz. 2017) because, in reaching this conclusion, we did not apply the aspects of the Fin

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Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A2024-29125. Public record. Not legal advice.