I am the leading scientific contributor to studies of West Indian boa genetics and genetic variation, an expert on West Indian boas in general, and the author of dozens of scientific papers on boas in the genus Chilabothrus. I am also the author of Reynolds et al. (2015) which was a focused population-genetic study on Chilabothrus granti, and I was an original reviewer of the SSA (USFWS 2018). I have also participated in 2018 surveys on the USVI Cay, as well as surveys for C. granti on Puerto Rico and Guana Island.

In short, and as others have stated in the public comments thus far, the scientific evidence does not support Delisting criteria 1–3. Below I will outline some of the key issues with assumptions in the proposal.

The proposed downlisting is based upon a key, but flawed, assumption: that the older surveys provide the best data on the populations.

1. Despite the apparent successes of conservation and population reintroduction for the species several decades ago, recent surveys in the last 5–10 years have shown a much different outlook for the species in the USVI. The largest small-island population, Cayo Ratones, is very likely extinct. From a previous estimated population size of ~500 individuals, representing nearly 1/3 of the census individuals in the USVI and Puerto Rico combined, this population is now likely gone following the passage of hurricanes Maria and Irma, as well as the recolonization of rats, as revealed by surveys in 2018.

2. The following passage from the proposed ruling: “However, because Virgin Islands boas are difficult to find, and the 2018 surveys were not extensive (e.g., did not survey the whole island), there is currently not enough evidence to conclude the Cayo Ratones population has been extirpated” (page 61703) is problematic. While technically true, it is misleading. Although it is plausible that they might not have been completely extirpated, there has almost certainly been a huge population decline on the island, which is of just as much concern. A density of hundreds of boas per hectare means that trained surveyors will absolutely encounter boas, even during brief surveys. That they did not see any is of significant concern. Also, rats are now back, and we know that rats and boas are incompatible on small islands (Tolson 1988). If the population is not yet extirpated, it likely soon will be.

3. The USVI Cay has been subject to comprehensive and repeated recent surveys, showing unequivocally that the population has declined from a density of 202 boas/ha in 2004 (Tolson 2004) to an estimated 45–110 boas/ha in 2018 (D. Smith et al. unpubl. data), as well as undergone a dramatic shift towards smaller body size. This is based upon two surveys periods consisting of nightly complete surveys of the island by experts over repeated nights. These surveys yielded a total of 64 individual captures. Further, the prey base of this island has shifted, as researchers have seen the extirpation of lizard prey species Ameiva exsul and Iguana iguana (non-native) (D. Smith et al. unpubl. data). A loss of prey species and a dramatic shift in body size might suggest that the long-term resiliency of this population remains questionable.

4. A significant population decline on Cayo Diablo is apparent from recent surveys. While some have questioned about whether those recent surveys are comprehensive enough, there is little reason to conclusively state that surveys from decades ago should provide the most compelling population size data, when the brief recent surveys suggest that the population is not nearly as dense as it used to be. The population was estimated to have a density of 105– 125 boas per hectare (Tolson 1991, 2004); but a survey conducted by Island Conservation in 2018 found encounter rates of 0.25 boas/hour on Cayo Diablo (Island Conservation 2018), which is far lower than would be expected given the previous density.

5. Statements about the St. Thomas population are misleading. For example: “Opportunistic observations have averaged about 10 observations of Virgin Islands boa per year since 2000.” (page 61708). These opportunistic observations frequently consist of dead individuals, which suggests high mortality. Between 1980 and 2006, 114 confirmed boa sightings were reported to the USVI Division of Fish and Wildlife on St. Thomas (Platenberg and Harvey 2010) and many of these were road-killed. But, no live boa has ever been found under survey effort on St. Thomas (R. Platenberg pers. comm. to G. Reynolds, August 2013). Further Harvey and Platenberg (2009) and Platenberg and Harvey (2010) also found that boas would have had about 800 ha of available habitat on St. Thomas, most of which is private land, and that nearly three-quarters of that habitat has already been developed.

In summary, the 2009 5-year review (USFWS 2009) concluded that only 1300–1500 Virgin Islands boas existed on Puerto Rico and the USVI. But estimates of population size in the BVI are hampered by lack of survey data. Since 2009, we expect that the population has further been cut in half with the apparent loss of the Cayo Ratones population and the decline in the USVI Cay population. All evidence points to a trend of decreasing number of populations and decreasing population size in remaining populations. This is not strong evidence for Criteria 1–3.

Comments on Problems with Interpretation of Genetic Data As I mentioned in my peer-review comments of the initial SSA, both the SSA and this proposed action are misunderstanding the implications of the genetic data available for the species.

1. Population Genetics of the VI Boa: Diversity and Divergence: Studies by Rodríguez- Robles et al. (2015) and Reynolds et al. (2015) showed that the species has a much smaller range than previously thought (when it was considered conspecific with Chilabothrus monensis on Isla de Mona). We now know that Chilabothrus granti is restricted to the eastern Puerto Rico Bank. Further, Reynolds et al. (2015) used genetic data and genetic data simulations to demonstrate that the population on St. Thomas has likely undergone a significant genetic and demographic bottleneck. This is especially relevant, as some of the captive and reintroduced populations are derived from St. Thomas founders, which suggests that these populations have now undergone serial bottlenecks. The expectation under that scenario is a greater magnitude of allelic loss. Until additional genetic data are available, our expectations are that the captive and reintroduced populations, which include the USVI Cay and Cayo Ratones, are moderately to severely genetically bottlenecked. Compounding this, when small populations exist at small size for multiple generations, our expectation is that genetic drift will yield a population genetic “relaxation” scenario, whereby alleles continue to be lost from the population at a predictable rate (mathematically predictable, that is, as estimated by the population genetic parameter theta; Reynolds et al. 2015). New population genetic studies are underway in my research lab and will undoubtably provide very valuable information relevant to the proposed down listing. These data should be available in 2021.

2. Proposing that C. granti is comprised of multiple units does not reflect the fact that the limited available genetic data clearly show that populations of the species across the Virgin Islands are interdigitated genetically, suggesting recent connection but not evolutionary distinctiveness that would mean they exist as independent units. Rodríguez- Robles et al. (2015) for example, showed that mitochondrial haplotypes/haplogroups from Culebra are also present on Tortola, Puerto Rico, and Cayo Diablo. In other words, they found Culebra haplotypes/haplogroups in nearly every other population they sampled.

3. The following statement regarding molecular phylogenetics: “More recently, molecular phylogeny work indicates that the genus Epicrates is paraphyletic (a group composed of a collection of organisms, including the most recent common ancestor of all those organisms), and the West Indian clade (as opposed to the mainland clade) was designated as Chilabothrus (Reynolds et al. 2013, entire). As a result, the Virgin Islands boa is now considered its own species.” While correcting this has little bearing on the Proposed Ruling, it shows that molecular data are not well interpreted. Reynolds et al. (2013) indeed showed that the genus Epicrates was paraphyletic. This led to recognition of the West Indian Boas as a separate genus, Chilabothrus, while mainland representatives remained Epicrates and Eunectes. But, the recognition of Chilabothrus granti as a separate species came from focal studies conducted by Rodriguez-Robles et al. (2015) and Reynolds et al. (2015), but was not codified until Reynolds and Henderson (2018). Both of these studies showed that the species previously recognized as Chilabothrus monensis sensu lato, occurring on both the Puerto Rico Bank and Isla de Mona, is in fact comprised of two very distinct species, which we now recognize as Chilabothrus monensis (Isla de Mona) and Chilabothrus granti (eastern Puerto Rico Bank). Misinterpretation of molecular phylogenetics (and missing relevant literature) does not auger well for the proper interpretation of more complex population genetic and demographic simulations to be incorporated into the proposed ruling.

Comments of the Species’ Distribution 1. It needs to be recognized that the record from Guana Island is dubious, and that it is almost certain that no substantial population of boas occurs there. On Guana Island, no boa has been officially recorded although anecdotal accounts exist from the 1930s (Grant 1932) and a snake fitting the description of a boa was apparently killed by groundskeepers there in the 1980s but never confirmed and the carcass was never examined (Lazell 1980; Mayer and Lazell 1988). No boas have been seen on Guana since. 2. Further, populations suggested to be on Necker, Great Camanoe, and Virgin Gorda are likely non-existent. Records from Necker and Virgin Gorda are anecdotal observations by a botanist (John G. H. Smith fide Mayer and Lazell 1988). According to Mayer and Lazell (1988), the Great Camanoe record is based on a specimen collected there and kept as a pet, but never verified to have come from that island (as opposed to having been captured on nearby Tortola). 3. Mayer and Lazell (1988) also suggest that a boa was captured on Jost van Dyke, and a recent publication (Island Resources Foundation 2009) matter-of-factly states that Virgin Islands boas are found on Jost van Dyke, although no photos or other evidence is offered. No official records of these boas exist on Jost; hence they are considered anecdotal without support. 4. “There is not enough information to reliably assess the status of Virgin Islands boa populations on those islands.”(page 61703) A more accurate statement is that there is little to no empirical evidence to suggest that robust populations occur on any of the British Virgin Islands.

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