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Virgin Islands tree boa

The Virgin Islands boa (Epicrates monensis granti), a blotched brown semi-arboreal snake, occurs on a number of islands from Puerto Rico eastward into the British Virgin Islands [1]. In the U.S. Virgin Islands, it is restricted to extreme eastern St. Thomas [2]. The Virgin Islands boa lives in subtropical dry forests where it hunts at night, eating mainly lizards asleep in trees [2]. During the day, the boas seek refuge in termite nests or under rocks and debris [3]. Although there are no current estimates of the number of Virgin Island boas that remain in the wild [3], they are rare and their current distribution is extremely disjunct indicating a history of extirpation and decline [2].

When conditions are favorable, this species can exist in high densities on small islands [1]. However, large-scale habitat destruction and the introduction of exotic mammalian predators have caused severe population declines [1]. The introduction of the Indian mongoose on St. Thomas, St. John, Tortola, and Jost Van Dyke contributed to population declines on these islands [3]. Feral and domestic cats, which prey on adult boas, have become ubiquitous on St. Thomas [1]. Two rat species, also introduced on many islands, are potential predators of young boas [3]. In addition, development on the east end of St. Thomas threatens the remaining boa population there [1]. Currently, the small, uninhabited cays and islets where much of the remaining populations have become concentrated tend to be vulnerable to inundations from the ocean and storms [4].

A Mona/Virgin Islands boa Species Survival Plan was developed in 1990 [1]. One of the first activities undertaken was a survey of localities likely to harbor previously unknown populations of the Virgin Islands boa [1]. One population was discovered on Isla Culebra, Puerto Rico but despite extensive surveys, no other new populations were found [1]. A captive breeding program, initiated by the Toledo Zoological Gardens in 1985, has proven to be quite successful [1]. By the mid-1990s, more than 100 offspring had been produced from ten founders [1]. Starting in 1993, reintroductions of captive-bred snakes were initiated [1]. Reintroductions on two islands, previously without boa populations but within their historic range, have been extremely successful [5]. On one of these islands, a population of 41 reintroduced boas increased over ten years to nearly 500 snakes [5]. On the other island, 42 snakes reintroduced in 1996 increased in number to 170 snakes within five years [5]. Through these efforts, Virgin Island boa populations have begun to increase dramatically [5].

[1] Tolson P.J, and M. A. Garcia. AZA Species Survival Plan Profile Mona/Virgin Islands Boa: A U.S./Puerto Rico Partnership Seeks to Recover Endangered Boa. Accessed at http://www.umich.edu/~esupdate/library/97.01 02/tolson.html
[2] Platenberg, R. J., F. E. Hayes, D. B. McNair, and J. J. Pierce. 2005. A Comprehensive Wildlife Conservation Plan for the U.S. Virgin Islands. Division of Fish and Wildlife, St. Thomas. 216 pp.
[3] USFWS. 1992. Species Account, Virgin Islands Tree Boa. U.S. Fish and Wildlife Service, Division of Endangered Species. http://www.fws.gov/endangered/i/c/sac0q.html
[4] American Zoo and Aquarium Association. 1998. Virgin Islands Boa 98 Fact Sheet. Accessed at http://www.nagonline.net/Fact%20Sheet%20pdf/AZA%20-%20Virgin%20Islands%20Boa%20Species%20Survival%20Plan.pdf
[5] Peter J. Tolson. 2006. Personal Communication.

Banner photo © Phillip Colla