Species

Caribbean islands exhibit high levels of unique biodiversity resulting from a long history of species colonizations and adaptations to geographically isolated conditions. The U.S. Virgin Islands host unique assemblages of unique terrestrial species, many of which are endemic to these islands. The suites of species found on St. John and St. Thomas are similar both to each other and to neighboring Puerto Rico due to their proximity and shared geological history. St. Croix’s distance from other islands and lack of connection to the Puerto Rican Bank has given rise to endemic species unique only to St. Croix. The range of terrestrial habitats offer niches for a variety of reptiles, amphibians, bats, and resident land and waterbirds, and the islands are important stopping off sites, both as a destination and for short refueling visits, for summer and winter migratory birds. Cays offer refuges for ground-nesting birds while coastal saline wetlands and guts provide critical food resources. The rich variation and connectivity within marine habitats, including coral reefs, mangroves, and seagrasses, offer habitat niches for an enormous variety of marine organisms, including fish, corals, molluscs, echinoderms, and others--too many to include in this document. The variation between islands also means that species that are common on one island may be absent or in decline on other islands. These distributional variations make territory-wide status assessments challenging. 

Additionally, geographic isolation combined with human-mediated species transport make it difficult to unravel biogeographic patterns. Localized threats may have significant impacts on isolated populations that potentially represent a significant portion of a species distribution within the region, but without consistent survey and monitoring effort across all islands, these differences are difficult to detect. The focus of limited research and monitoring resources are distributed differently on each island, based on species distributions and personnel expertise. 

Terrestrial and marine species in the Caribbean have experienced high levels of population declines and extinctions due to habitat conversion and degradation, encroachment, and invasive species, coupled with stochastic events such as hurricanes and other disturbances. Corals and other marine organisms are increasingly affected by rising ocean acidification and sea surface temperatures, and increasingly severe hurricanes, precipitation events, and droughts create unprecedented impacts to both marine and terrestrial species.

2025 Update

The suite of species that have been designated as SGCNs were designated as such through a multi-step process combining historical records, expert review, literature surveys, and existing territorial and federal listings. We additionally listed Species of Greatest Information Need (SGIN) if the species were identified by respondents, or were previously listed as SGCN, without any additional information available to make a determination at this time. 

New to the USVI SWAP in this 2025 update, is: 

• an analysis of the USVI SGCNs in the Regional Context 

• a comprehensive plant list 

• terrestrial invertebrates 

• freshwater species 

• range maps for select species

Plant Working Group: A working group made up of expert botanists from all three islands developed a list of plants most in need of conservation. They started with from a review of recent major botanical publications, landscaping consultants, government agencies, and historical documents and based on current needs and prioritizations, and narrowed the list to 66 species which are now part of the SGCN list. The working group worked over three years and was facilitated by Division of Fish and Wildlife to aggregate the plant lists, review all candidate species, and justify their inclusion as SGCN (Guyant et al, in preparation). 

Freshwater Fauna: Through a C-SWG, the Southeast Aquatic Resources Partnership and Clemson University conducted surveys across the territory for freshwater fauna. One of the components to this project was to develop a list of suggested SGCN for freshwater fauna based on survey results. 

Terrestrial Invertebrates: Through a partnership with the Southeast Climate Adaptation Science Center, we were able to add a list of terrestrial invertebrates. This list was based on a review of all verified observations through GBIF, specimen collections, and recent surveys by the USGS Bee Lab. Although most terrestrial invertebrates continue to be data deficient, we will be able to work toward filling those data gaps for the next SWAP update.

Range Maps: In previous USVI SWAPs, distribution of species was based exclusively on SGCNs' associations with habitats. Through a partnership with WildMon, range maps for 83 SGCN were produced. These species were selected based on the availability of sufficient occurence data. Range maps were developed from occurrence records derived from GBIF records supplemented by Acoustic monitoring conducted by WildMon, and the USGS Gap Analysis. Column L indicates which species were mapped and Column M indicates the total area of the Extent of Occurrence (EOO) which describes the potential broad-scale geographic extension of species beyond just the observed occurrences. 

For species in which there was not sufficient information to produce a range map, their USVI distribution continues to be reflected by their association with habitat types, unless otherwise noted.

U.S. Virgin Islands Species of Greatest Conservation Need

Methods for assessing species' status:

Each species was scored using criteria such as known population trend, rarity, range contraction, threat exposure, and potential for management intervention. Without national metrics, like NatureServe, which does not the serve the USVI, so we lack things like S-Ranks and G-Ranks for our jurisdiction, and without inclusion in other ranking metrics for example the regional Species of Greatest Conservation Need Assessments (animals and plants), we had to create our own metrics. In some cases, we have data because species are assessed through federal partnerships, for example, when species are listed under the Endangered Species Act which prompts the USFWS and NOAA to assess species or when a species is assessed internationally by the Convention for the International Trade of Endangered Species and added to an Appendix. Thus, we choose criteria based on best-available science and evaludated each species individually. Possible criteria based on stakeholder and expert feedback included: 

Threat exposure / severity 

How many threats affect the species, and how severe those threats are 

Trend / decline 

Whether the species is declining, stable, or unknown 

Rarity / distribution 

How restricted its range is (is it geographically limited within the USVI) 

Habitat vulnerability / loss risk 

How threatened its habitat(s) are (e.g. high land‐use change) 

Feasibility of conservation action 

Whether practical intervention is possible (cost, risk, social/political constraints) 

Data availability / knowledge gaps or expert elicitation 

Whether there is enough information to act confidently, or whether data deficiency increases uncertainty (for prioritizing research) 

Multiplier / leverage potential 

If acting on this species also benefits many others (e.g. umbrella, keystone) or expert elicitation is used for confidence 

We created an expert elicitation framework with two types of uncertainty measurements. We are binning elicitation data into ranks for conservation action prioritization, detailed below.

The species were ranked for conservation status (Status Level). A guided workshop and media outreach resulted in eliciting over a dozen experts feedback to inform indicators of confidence (Confidence Star Ranking) and uncertainty (Confidence Category) used in assigning the final conservation status by the  USVI Division of Fish and Wildlife biologists: 

Expert Elicitation Ranking System chosen for the 2025 SWAP

1. Status level → Base Score 

1. Very High Concern = 5 

2. High Concern = 4 

3. Medium Concern = 3 

4. Low Concern = 2 

5. Blank / Not specified = 1 

2. Confidence (stars) → Multiplier 

1. ★★★★★ = 1.2 

2. ★★★★☆ = 1.1 

3. ★★★☆☆ = 1.0 

4. ★★☆☆☆ = 0.9 

5. ★☆☆☆☆ = 0.8 

6. ☆☆☆☆☆ = 0.7 

3. Confidence (categories) → Multiplier 

   1. 1. 1. High Confidence = 0.9

         2. Some Confidence = 0.5

         3. Low Confidence = 0.1

         4. No Confidence = N/A

4. Priority Score = Status Base × Confidence Multipliers

This ensures that species with higher concern and higher confidence in the data rise to the top, while lower concern and low confidence species get a smaller score. 

The tiers from the expert elicitation for the Species of Greatest Conservation Need are now as follows:

1. Low Risk - if no conservation action occurs, the species will likely not be affected - HIGH RELATIVE ABUNDANCE

2. Medium Risk - conservation action is warranted - RELATIVELY ABUNDANT BUT THREATS EXIST

3. High Risk - conservation action is needed in order for the species to persist - LOW RELATIVE ABUNDANCE 

4. High Risk (possibly Extinct) - conservation action is needed to determine if the species persists - POSSIBLE NO ABUDANCE

5. Species of Greatest Information Need - it is unknown, but likely, that conservation action is needed. The species was identified as a new or existed previously as a Species of Greatest Conservation Need in 2015 and/or 2005 with no new information available. - NO POSSIBLE WAY TO ASSESS ABUNDANCE

Species Ranges and Occurrence

1. A checklist of 1,842 species observed in the citizen science platform iNaturalist: https://www.inaturalist.org/check_lists/13080-Virgin-Islands-Check-List Species can be individually viewed for location observed. 

2. DFW Wildmon Acoustic Data across 150 USVI sites focused on amphibians and birds – find site and species lists here: https://dashboard.wildmon.ai/project/usvi-dfw-biodiversity-monitoring   were used to create range maps. If a range map was created, it is now indicated in the species table. Please refer to the species table.