Endangered Reptiles and Amphibians of the World - I. The Bimini Boa, Epicrates striatus fosteri.

by Ryan Potts

Introduction

The Bimini boa (Bimini Island boa; Epicrates striatus fosteri; Barbour 1941) is one of eight recognized subspecies of the insular Haitian, Fischer's, or Hispaniolan boas, endemic to the Bahamas and Hispaniola in the West Indies. Several hundred islands, islets and keys lie within the Bahamas. All of the landmasses are of low elevation (0-40 m). Although some contained well-developed lowland rainforest at the time of discovery by Europeans in the sixteenth century, only sparse secondary forests are present today. Aside from the Bimini boa, the remaining Haitian boas residing in the Bahamas are the Cat Island boa (E. s. ailurus), the Berry Island boa (E. s. fowleri), similar in appearance to E. s. fosteri, the Ragged Islands boa (E. s. mccraniei), and the Nassau, Eleuthra Islands, or New Providence Island boa (E. s. strigulatus). The Hispaniolan forms include Fischer's or Haitian boa (E. s. striatus), the Tiburon Peninsula boa (E. s. exagistus), and the Ile de la Tortue boa (E. s. warreni).

Several of the insular Epicrates are presently considered endangered species, including the Puerto Rican boa (E. inornatus), Virgin Islands boa (E. monensis ssp.), and Jamaican boa (E. subflavus). In addition to being locally protected, all of the aforementioned snakes are listed in the World Conservation Union (IUCN) Red List of Threatened Animals (IUCN 1996) and by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) on Appendix I. The Hispaniolan populations of Haitian boas are not currently considered threatened, although several of the Bahamian subspecies are (Tolson and Henderson, 1993). The Bimini boa is protected locally by the Bahamian government and is listed in the IUCN Red List of Threatened Animals (IUCN 1996), although the extent to which the animal is threatened has not yet been evaluated.

Appearance

Bimini boas are relatively long, slender animals, possessing proportionately long tails. Adult males are capable of reaching a maximum length of ~2.6 m in length, with females being slightly smaller at ~2.2 m. The head is well set off from the neck and lacks heat sensitive pits on either the upper or lower labials. Typical adult specimens possess a faded pattern consisting of gray to brown jagged markings, on a dark brown or black background dorsally. A stripe travels laterally from the back of the head, down the neck, to the upper part of the body. The dark stripe is contrasted with a lighter parallel stripe and, overall, the skin displays a large degree of iridescence. Ventrally, the snakes may be uniformly cream, brown, or gray in coloration, or possess blotched patterns of these colors.

Juvenile Bimini boa
Juvenile Bimini boa.

Bimini boas can reach sizes of approaching 2.5 m, or 8 feet.

Natural History

The Bimini boa is distributed on four islands in the Bahamas: North Bimini Island, South Bimini Island, East Bimini Island, and Easter Cay. The islands are very small however. For example, the largest point on North Bimini is only ~650 m wide. In addition, within its meager range limited suitable habitat for the snakes is found. The boas have become scarce on North Bimini due to extensive development, and the pet trade heavily exploited Southern Bimini stock despite local protection (Tolson and Henderson, 1988).

As is typical for many of the insular Epicrates, young Bimini boas are generally arboreal in nature. Adults can often be found both on and above ground. Forested terrain is usually preferred.

Young Bimini boas predate in the wild on small lizards, i.e. Anolis, progressing onto birds and small mammals as they grow. The snakes may also prey on domestic fowl. Active hunting generally occurs at night, both on the ground and in trees.

Juvenile Bimini boa
Juvenile Bimini boa.

Bimini boas often prefer to burrow underground, waiting to ambush unsuspecting prey.

Captive Care

The Bimini boa is usually very amenable to life in captivity, once the initial problem of feeding the newborn has been overcome. Bimini boas, in my experience, are generally docile and gentle in temperament and feed readily on thawed rodents of appropriate size. The snakes have a habit of burying in the substrate given the opportunity, for which purpose I use aspen bedding. Care should be taken when performing routine vivarium maintenance and cleaning, as the snakes will erupt from their burrows if an object moves within striking range. A snake hook is, therefore, recommended when removing animals from their enclosure.

When placed into a decoratively designed arboreal vivarium, with good lighting to highlight the snake's natural iridescence, a very attractive display is produced. The snake's large size and relatively active lifestyle does necessitate a large enclosure, however, complete with sturdy branches for the snakes to bask on. Many Haitian boas like to bask when resting off the ground, so provision for a basking 'perch' is recommended. This species can be housed together, although, males should be closely watched to prevent injury during agonistic breeding behavior. As always, animals should be separated prior to feeding to avoid accidental injury.

Reproduction

Little is known of the reproductive biology of Bimini boas in the wild, although the snakes have been bred in captivity by both zoological gardens and private keepers on several occasions. E. striatus ssp. is generally a seasonal breeder in captivity (Tolson and Henderson, 1988), with courtship occurring from February through May, and parturition taking place between August and October. Wild-caught Epicrates, that were gravid at the time of capture, will usually give birth during this period; a time coinciding with the abundance of hatchling Anolis. Mating activity can be stimulated in captivity by a reduction in temperature during the winter combined with an increase in humidity during springtime. Male combat has also been reported (Tolson and Teubner, 1987), in the form of typical boid wrestling bouts as well as the release of the contents of their scent glands. Nevertheless, successful reproduction in captivity has occurred without multiple males being present. Aggression towards other snakes is not uncommon during periods of reproductive activity in the insular Epicrates. This aggression is not necessarily restricted to male snakes, as Tolson (1994) noted a female Puerto Rican boa (E. inornatus) killed and consumed a male partner. Active spurring by male Epicrates prior to mating with females is also common.

E. s. fosteri give birth to a relatively large clutch of moderately sized neonates (~15 g each). Bartlett (1990) reports that a large captive Bimini boa, 2.5 m in length, gave birth to a litter of 29 neonates. The newborn snakes undergo their first ecdysis shortly after birth, and feeding has been reported to occur within a fortnight of birth (Ross and Marzec 1990), although more commonly following their second ecdysis. As in the wild, neonates prefer lizards as their initial food, rendering tube-feeding minced baby mice likely until the snakes can accommodate lizard-scented baby mice alone. Captive female insular Epicrates will usually breed every other year, although whether this is the situation in the wild is uncertain.

Adult Bimini boa
Adult Bimini boa.

Endangered Status

The Bimini boa finds itself in a very precarious position in the wild. Significant loss of habitat through development, the introduction of feral animals that prey on the boas, in particular rats and cats, and over-zealous collecting for the pet trade have all contributed to the demise of the snakes. The future of Bimini boas in the wild indeed looks bleak. Ever dwindling natural habitat combined with over-population by man and use of the Bimini Islands for recreation and tourism, in particular the fishing industry, would suggest that eradication will continue from the remaining available habitats.

Several zoos and private individuals maintain small collections of the boa, although, whether sufficient numbers of the animals are present in captivity to sustain a viable population remains to be seen. The future release of captive-bred boas to their natural range does not, at this time, appear viable, due to the lack of suitable habitat available. Reintroduction, even when seemingly suitable habitat exists, is nevertheless problematical. For instance, the introduction of foreign diseases to which native snakes have no resistance is one such problem. As is the case with many of the worlds' animals, a life in captivity may be all that is available to this beautiful boa.

Further Reading

There is scant information available in the literature regarding Bimini boas. A good source of reference for the insular Epicrates is 'The natural history of West Indian boas', by Tolson and Henderson, as listed below, and Schwartz and Henderson's 'The amphibians and reptiles of the West Indies: descriptions, distributions, and natural history' (University of Florida Press, USA, 1991). More general information on boas can be found in 'The living boas, a complete guide to the boas of the world', written by Jerry G. Walls (TFH Publications, USA, 1998), and 'Captive husbandry and propagation of the boa constrictors and related boas' by David Fogel (Krieger Publishing Company, 1997).

References

Barbour, T. (1941) A new boa from the Bahamas. Proceedings of the New England Zoological Club, 18, 61-65.

Bartlett, R.D. (1990) Insular and 'Dwarf' Boas of the New World. Reptile and Amphibian Magazine, May/June, 38-47.

1996 IUCN Red List of Threatened Animals. IUCN Publications, Cambridge, UK, 1996, 448 pp.

Mattison, C. Keeping and Breeding Snakes. Blandford, London, UK, revised edition, 1998, 224 pp.

Ross, R.A. and Marzec, G. The reproductive husbandry of Pythons and Boas. Institute of Herpetological Research, California, USA, 1990, 270 pp.

Tolson, P.J. The reproductive management of the Insular species of Epicrates (Serpentes: Boidae) in captivity. In: Captive Management and Conservation of Amphibians and Reptiles. Society for the Study of Amphibians and Reptiles, Ithaca, NY, USA, 1994, pp. 353-357.

Tolson, P.J. and Henderson, R.W. The natural history of West Indian boas. R & A Publishing Limited, Somerset, UK, 1993, 125 pp.

Tolson, P.J. and Teubner, V.A. (1987) The role of social manipulation and environmental cycling in propagation of the boid genus Epicrates: lessons from the field and laboratory. American Association of Zoological Parks and Aquariums Regional Conference Proceedings, 606-613.


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