The Service is proposing to list the Puerto Rican skink, Lesser Virgin Islands skink, and Virgin Islands bronze skink as endangered species under the Endangered Species Act (ESA) due to threats from non-native predators and habitat loss and degradation from development. 

The Service is also proposing to list the Culebra skink as a threatened species with a species-specific 4(d) rule. Threats to Culebra skink are non-native predators, habitat loss and degradation from development, and sea level rise and storm surge from a changing climate. The proposed 4(d) rule provides for the conservation of the Culebra skink by allowing some exceptions that incentivize conservation actions or only have a minimal level of take of the species. Proposed exceptions include predator control or eradication efforts and habitat restoration efforts that are expected to have negligible impacts on the skink and its habitat.

Critical habitat is also being proposed for these skinks; 143,947 acres of critical habitat for the Puerto Rican skink on Puerto Rico and Desecheo Island; 477 acres of critical habitat for the Lesser Virgin Islands skink on Hans Lollik Island, U.S. Virgin Islands (USVI); 392 acres of critical habitat for the Virgin Islands bronze skink on Water Island, Buck Island, and Turtledove Cay, USVI; and 5,648 acres of critical habitat for the Culebra skink on Culebra Island and surrounding cays. All units of proposed critical habitat are considered occupied by the associated species.

Predation by non-native mammalian predators like mongoose and cats, historically and currently, is the greatest threat to each skink species. Other influences on skink viability include habitat degradation and fragmentation from development, storm surge and impacts from hurricanes, and sea level rise as the result of climate change climate change
Climate change includes both global warming driven by human-induced emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century humans have had an unprecedented impact on Earth's climate system and caused change on a global scale.

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There is very little population information for these skink species. For each island population, the Service considered populations extant (still present on the landscape) if they have been detected since 2000. As such, there are no precise population estimates for these species.

All of these skink species have similar patterns and coloration, generally some shades of tans and browns, with a pair of dark stripes on their sides and limb pattern, if present, with spots or blotches. 

These skinks are thought to spend most of their time out of sight under some type of substrate. However, they are often observed basking in the sun on rocks, leaf litter, and fallen logs in forest habitat, they are cold–blooded and rely on air and soil temperatures to maintain their body heat. They have also 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.

When the Service proposes a species for listing under the ESA, we are required to consider whether there are geographic areas that contain essential features or areas that are essential to conserve the species. If so, we may propose designating these areas as critical habitat.

The Service is proposing to designate 143,947 acres of critical habitat for the Puerto Rican skink on Puerto Rico and Desecheo Island; 477 acres of critical habitat for the Lesser Virgin Islands skink on Hans Lollik, U.S. Virgin Islands (USVI); 392 acres of critical habitat for the Virgin Islands bronze skink on Water Island, Buck Island, and Turtledove Cay, USVI; and 5,648 acres of critical habitat for the Culebra skink on Culebra Island and surrounding cays.  

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Image Details

The Mona skink only occurs on Mona Island where it can be found in several areas. Mona Island is a nature reserve managed for conservation with limited human development, impact on them from non-native predators is low, and the risk of storm surge is low due to the high elevation of the habitat. Although the species is impacted by some threats across its range (mostly predation from feral cats), the Mona skink’s viability is such that no current threat is acting at an extent or severity to jeopardize the existence of the species throughout all of its range. Therefore, it does not warrant listing at this time.

The Greater Virgin Islands skink has not been seen since 1877. With considerable survey effort expended by qualified researchers over several decades on both St. Thomas and St. John where the species once occurred, it is highly likely that the species is extinct. The loss of the Greater Virgin Islands skink can be attributed to predation by the mongoose. Therefore, listing is not warranted due to likely extinction.

The Greater St. Croix skink has not been seen on St. Croix for over a century, and none have been seen on Green Cay for nearly a quarter of a century. As with the Greater Virgin Islands skink, considerable survey effort has been expended by qualified researchers over several decades on both St. Croix and Green Cay where the species once occurred. Despite these efforts, no individuals have been found and the species is likely extinct. The loss of the Greater St. Croix skink can be attributed to predation by the mongoose. Therefore, listing is not warranted due to likely extinction.

The Lesser St. Croix skink has not been seen on St. Croix for over a century. Historically known from St. Croix, USVI and described from only one specimen collected in 1875, considerable survey effort has been expended by qualified researchers over several decades on St. Croix. Despite these efforts, no individuals have been found and the species is likely extinct. The loss of the Lesser St. Croix skink is mainly attributed to predation by the mongoose in addition to habitat loss. Therefore, listing the Greater St. Croix skink is not warranted due to likely extinction.  

To submit comments on the proposed rule, go to the Federal eRulemaking Portal:  http://www.regulations.gov. In the Search box, enter FWS–R4–ES–2024–0154, which is the docket number for this rulemaking. Comments on the proposed rule must be received by February 18, 2025. We must receive requests for public hearings, in writing, at the address shown in FOR FURTHER INFORMATION CONTACT by February 3, 2025.

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 786-244-0081; correo electrónico: caribbean_es@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.