Re-introduction of the Virgin Islands boa to the Puerto Rico Bank

Summary

The Virgin Islands boa (Epicrates monensis granti), a small, nocturnal snake endemic to the disjunct islands of the Puerto Rico Bank, was reduced to fragmented remnant populations by habitat loss and introduced black rats, cats, and mongoose, earning US Endangered Species Act protection. Starting in 1984, Toledo Zoo and Puerto Rico and US Virgin Islands wildlife agencies ran a nine-year natural history study yielding over 650 captures of more than 300 marked snakes, informing a 1985 cooperative captive breeding program that achieved the first successful captive birth in 1986 and an AZA-sanctioned Species Survival Plan by 1990. Four potential release sites were selected using Principal Components Analysis of habitat and prey data, and black rats were eradicated at each using repeated bromadiolone baiting, confirmed rat-free by chew-stick monitoring. Before release, snakes were tested for their willingness and ability to hunt live Anolis cristatellus lizards, their natural prey, with all but two of 31 adults tested succeeding immediately, then quarantined 30 days and implanted with transponders. In 1993, 28 captive-born boas from seven zoos were released, with 13 more through 1995; a parallel translocation program moved 31 wild snakes from St. Thomas starting in 1996, joined by 11 more captive-born snakes in 2002. A ten-year evaluation found the Puerto Rico site population had grown from 41 to nearly 500 snakes, and the US Virgin Islands site from 42 to about 170. The project rated itself Highly Successful, citing high initial survival and multiple reproductive events across years.