Virgin Islands Tree Boa

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Virgin Islands Tree Boa

Epicrates monensis granti

ListedOctober 13, 1970
FamilyBoidae (Boa)
DescriptionModerate-sized tree boa with light brown back covered with dark brown blotches.
HabitatOpen woodlands of subtropical dry forest and coastal forests.
FoodAnole lizards, mice, small birds.
ReproductionLive young, two to ten in a litter.
ThreatsIntroduction of non-native species, killing by island inhabitants, construction.
RangePuerto Rico, U.S. Virgin Islands


The Virgin Islands tree boa is a moderate-sized tree boa that grows 3-4 ft (0.9-1.2 m) in length. It has a light brown back covered with dark brown blotches, while its cream-colored underside is speckled with grayish-brown. It is nonvenomous and harmless to humans.


The Virgin Islands tree boa is active at night and during the twilight and dawn hours. It seeks cover during the daylight hours. It mates between February and May, and the live young are born in August and September. It is thought that the females reproduce every other year, and that the young take three to five years to mature. There are two to ten young in a litter. There is no evidence of parental care. Anole lizards make up the bulk of the boa's diet, along with occasional mice or small birds.


Virgin Island tree boas live in the open woodlands of subtropical dry forest on the steep slopes of the islands but can also inhabit coastal forests of low sandy islets as well. Snakes on Cayo Diablo occupy groves of sea grapes, open mixed scrub, tangled vegetation, and cocos palms. At night, they crawl on the vegetation; during the day they have been observed resting beneath loose sections of termite nests, in palm axils, and under debris. Since they are nocturnal and must conceal themselves during the day, shelter availability seems to be an important habitat requirement.


While another subspecies of this snake, the Mona boa (Epicrates monensis monensis ), is found on Mona Island just west of Puerto Rico, the Virgin Islands tree boa is found on several islands east of Puerto Rico, including Cayo Diablo, Tortola, and the eastern end of the island of St. Thomas. The species has not been sighted for some time on Great Camanoe Island, Necker Cay, Guana, Virgin Gorda, or several other islands and cays, though it may still exist on these islands.


The introduction of non-native species such as the mongoose, rats, and feral cats has caused much of the decline in boa numbers. Island inhabitants often kill any snakes on sight, while new construction on St. Thomas also threatens that small population. The small uninhabited cays and islets where much of the population is now concentrated are vulnerable to inundations from the ocean and storms.

Conservation and Recovery

The Virgin Islands tree boa is listed as an endangered species by the U. S. Fish and Wildlife Service (FWS) and is an Appendix I species under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). The government of Puerto Rico has also given the boa threatened species status. There are no estimates of the number that remain in the wild, but it has always been rare. Rat eradication programs have begun on offshore cays slated as reintroduction sites. Twenty-eight zoo-born individuals were released on Cayo Ratones, Puerto Rico, in August 1993, after rat eradication was completed. Long-term ecological and demographic studies are also being conducted on Puerto Rico. Some efforts have been made on Puerto Rico and St. Thomas to show residents that the boa is harmless and highly endangered. There are about 107 Virgin Island tree boas in North American zoological facilities. Captive propagation is part of the FWS recovery plan for this species.


U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
1875 Century Blvd., Suite 200
Atlanta, Georgia 30345

U. S. Fish and Wildlife Service
Boquerón Ecological Services Field Office
P. O. Box 491
Boquerón, Puerto Rico 00622-0491
Telephone: (787) 851-7297
Fax: (787) 851-7440


American Zoo and Aquarium Association. "Virgin Islands Boa Species Survival Plan."

U. S. Fish and Wildlife Service. 1984. "Mona Boa Recovery Plan." U. S. Fish and Wildlife Service, Atlanta. 14 pp.