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JAMAICAN BOA
Scientific name – Epicrates subflavus
Credit: James Morgan
Background
The Jamaican boa, or ‘yellowsnake’ as it is locally known, is threatened with extinction in the wild in its
native Jamaica. Once common throughout the island, the snake has suffered a long history of decline, which
began with colonization by Europeans in the 16th Century. Introduced mongoose, dogs, cats and pigs,
together with the inevitable habitat destruction and persecution by people, are the main culprits.
Durrell Wildlife became involved in a captive breeding programme to help conserve the species in 1976,
when 7 boas were brought to Jersey Zoo. Since then hundreds have been bred and sent to other zoos taking
part in the management of the captive population.
Species classification
Boas are a primitive kind of snake, closely related to the pythons of Africa and southern Asia. The males have 2 small
spurs at the base of their tail, which are the evolutionary remnants of hindlimbs - snakes actually evolved from
ancestral lizards. The Jamaican boa is one of 10 closely related snake species in the group or genus Epicrates, which
are distributed throughout Central and South America and the Caribbean. Epicrates subflavus is found only in Jamaica.
The Jamaican boa should not be confused with the common boa or Boa constrictor, which is a completely different
species, found throughout Central and South America.
Description
The yellowsnake has variable colouration, but some individuals may indeed be almost entirely yellow. More typically
though, the boa’s front end is largely a golden yellow, orange to reddish brown, darker on the back than the sides and
belly. This background colour is marked with variable amounts of black spots, which become denser further down the
body to become irregular black bands by the middle section. The back half of the snake’s body is dark blue-black,
mainly solid, but with some irregular markings. The top of the boa’s head is usually a duller colour, either grey or olive
green, with a black stripe behind each pale yellow / brown eye. In sunlight the scales reflect a rainbow of iridescence,
which is most clearly seen on the dark back end of the snake’s body.
Baby Jamaican boas are pale orange with dark orange or brown crossbands and a paler pinky-orange belly. In captivity
they develop adult colouring at about 1½ years old. Adult females are generally larger than males and they can reach a
length of 2½m (8ft) and 2m (6ft) respectively and weigh at least 5kg (10½lb). These boas can live in captivity for over
30 years.
Distribution and habitat
As their name implies, the Caribbean island of Jamaica is the only place that these boas live in the wild. They are found
in a variety of habitats including humid tropical and montane forest, dry limestone scrub-forest, woodland, swampland
and mangrove. There is little information on the snake’s numbers, whereabouts and habitat preferences, but its
distribution over the island suggests that changes in land use by humans and the killing of snakes have led to a recent
isolation of populations.
Feeding habits
Like many boas, the yellowsnake has strongly arboreal habits and spends much of its time up in the trees. It has also
been recorded to search for prey at ground level, which may be due to changes in its environment and food source (i.e.
decrease in forest, increase in rodents) since people arrived. Jamaican boas are mainly nocturnal (active at night) and
usually stay well hidden during the day either in dense foliage, tree holes, rock crevices or underground burrows.
However, they do bask in the sun and may be seen lying on rocks to warm up in the early morning. During dry weather
they also venture out in search of water.
Jamaican boas hunt a variety of small animals, usually by ambushing them. Their prey includes rats, bats, birds, lizards,
frogs and the occasional mongoose (also an enemy of the snake), which they detect using their forked tongue. Boas are
non-venomous and kill their prey by constriction. They use their needle-sharp teeth to catch and hold their prey, which
is suffocated in the coils of the snake’s muscular body. Once the prey is dead, the snake eats it whole and head first,
using its teeth and throat muscles to ease the animal down. In the Zoo an adult snake is fed pre-killed rats or small
chickens every 1-2 weeks.
Breeding
Changes in temperature, day length and rainfall are thought to stimulate breeding in Jamaican boas, and mating usually
takes place both in the wild and captivity between February and April. Males compete for the chance to court a female
by each releasing a distinctive scent or ‘pheromone’, she then mates with the male that exudes the most desirable scent.
A female may mate with several males during the mating season. During copulation a pair of snakes may remain
entwined for up to 24 hours and may do this several times over a period of days. Male snakes do actually have two
penises or ‘hemipenes,’ but only ever use one during a bout of mating. Occasionally a hemipene may be ripped off
when mating snakes disengage suddenly, and then the ‘spare’ is rather useful.
Although the boas do produce eggs, the female retains them in her body for the 6-7 months that it takes the young to
develop. During development, the embryonic snakes are each encased in a transparent membrane, which lies beneath
the shell of egg-laying species. Once they have absorbed the yolk of their eggs, they ‘hatch’ inside the female by
breaking out of their membranes and are then born fully formed and immediately active. A female may produce from 5
to 44 babies at one time, depending on her size, and after the birth she plays no further part in their lives. A female at
Jersey Zoo holds the record of 44 offspring. In the wild many of these would fall victim to predation or starvation, but
in the security of the Zoo we are able to ensure a high rate of survival for young snakes. A baby Jamaican boa is about
50cm long and weighs around 15g (½oz).
Conservation status
The World Conservation Union currently classifies the Jamaican boa as Vulnerable on the Red Data List (IUCN,
2000). This means that it faces a high risk of extinction in the wild in the medium-term future (within the next 100
years). The species is also listed under Appendix I of CITES (the Convention on International Trade in Endangered
Species of Wild Fauna and Flora). This affords it the highest degree of legal protection against international trade.
However, Jamaican law does not protect the boa and most people kill it on sight because they think it is dangerous.
The approximate distribution of the snake is known from past surveys. The most recent of these was by carried out by
the Head of the Durrell Wildlife Herpetology Department in 1995. However, an accurate assessment of their numbers
has proved impossible, owing to the snake’s very shy and elusive nature. However, it is known that the yellowsnake
was once common in many of Jamaica’s 13 parishes. The introduction by humans of animals such as dogs, cats,
mongoose and pigs, is thought to be largely responsible for the boa’s decimation. Pressure on the fragmented and
dwindling population continues to increase as there are few places left for the snakes to seek refuge. The growing
human population is using more and more land for housing, farming, mining and tourism and continues to slaughter the
harmless boas because of fear and ignorance.
Jamaica’s own, appropriately named, Hope Zoo is throwing a lifeline to the island’s native boa and other endangered
wildlife. An education programme initiated by a graduate of Durrell WIldlife’s International Training Centre has begun
to change people’s attitudes, by spreading the awareness that Jamaica’s animals are special and in danger of
disappearing forever. Children are particularly receptive to this ‘protection through pride’ approach and are learning
that the Jamaican boa is not only very beautiful, unique to their island and harmless to people, it also helps them by
controlling non-native rats that spread disease and eat their crops.
In the Zoo
Our adult boas are kept in a group on display in the reptile house, where they make a stunning exhibit and are a firm
favourite with visitors (at least, with the ones who like snakes!). Their babies are housed in separate cages in the
behind-the-scenes breeding facility, so that their food intake and growth can be carefully monitored. They are offered
food once a week, which is a dead mouse of an appropriate size.
The snakes kept here in Jersey are very valuable members of an international captive breeding programme for their
species. The success of their breeding efforts and our reptile staff’s rearing technique has resulted in hundreds of
offspring being sent to other zoos either as founders for a new colony or to add ‘fresh blood’ to an existing one. To help
manage the growing number of Jamaican boas kept in captivity worldwide, an ‘International Studbook’ has been
compiled. This regularly updated document keeps track of individual boas and coordinates their breeding and
movement between zoos, which keeps the population genetically healthy.
The future
The continued success of the captive breeding programme gives the Jamaican boa a ‘safety net’ should the worst
happen to the species in the wild. It is hoped that further work in Jamaica will enable the protection of the boa’s
remaining habitat, restore degraded areas and bring about some form of legislation to prevent snakes being killed so
readily. These measures combined with the public education campaign will hopefully make it possible get the species
off the Red List one day.
March 2001