Snakes at Bristol 1: Aruba Island Rattlesnake

Aruba Island Rattlesnake

After a long break, the review of the various species held at Bristol continues with the snake collection. Bristol Zoos’ reptile department has bred several snake species over the years, but the main focus at present is on Asian turtles and amphibians.

Grey-Banded Kingsnake - a commonly kept pet snake

As with most zoos, the collection of snakes at Bristol concentrates on non-venomous, larger terrestrial species that feed, or can be trained to feed, on rodents. This may give the public a false picture of the true diversity of snakes, as there is a huge variety of sizes, shapes, dietary habits, and ecological niches occupied by the world snake species. Generally, invertebrate feeders are smaller, secretive, often harder to maintain in good health, and do not make good display animals. Fish eating specialists can be maintained more easily, but also may not make such good display animals, and also the marine fish eaters are almost invariably venomous, which is an additional hazard to keepers.

Gaboon Viper - seldom seen even in zoos

Terrestrial venomous species are not necessarily in themselves harder to look after than constrictors, but keeping them requires stocks of expensive antivenom to be kept on hand, plus additional safety precautions and insurance to cover all eventualities. With so many good non-venomous species available, very few zoos keep dangerous species. In the UK, London and Chester zoos have good examples of some of the most dangerous snakes in the world, such as Gaboon Viper, Black Mamba and King Cobra. It goes without saying that these are certainly not snakes to be kept by private individuals, and the Dangerous Wild Animals Act in the UK requires anyone who keeps a venomous snake to be licenced and inspected by the local authorities.

Yellow-Bellied Sea Snake - venomous, never seen in captivity

Having said that, the first snake visitors encounter at Bristol will be a venomous snake, the Critically Endangered Aruba Island Rattlesnake, Crotalus durissus unicolor. Confined to Aruba Island in the Caribbean, it is a local subspecies of the much more widespread South American Rattlesnake, and at a maximum length of around 1m is dwarfed compared to its mainland cousins. It is also unfortunately one of the rarest snakes in the world, with an estimated wild population of under 250 animals at best. The reasons for this are both natural and human generated – Aruba is not large and is also quite arid, so there is not a lot of food to supply a large population at the best of times. With the large human population on the island suitable habitat has been lost, and rattlesnakes are not exactly popular with people in any part of the world, so any encounters with humans tend to be fatal to the snake. As a result, the total natural range is now the interior of the island, with a maximum extent of 75 square kilometres, and most of the population is found in only half that area. Unfortunately, overgrazing by goats has adversely affected the habitat, and the Common Boa has also recently colonized the island and may compete with them.

In the wild, they seem to feed mainly on rodents, along with the common whiptail lizards. Captive individuals can be maintained on rodents, with adults taking 2-4 mice per month. Studies are needed though on whether this level of food intake is possibly too much – obesity is a common problem with less active species of snakes such as vipers or pythons in captivity, partly because individuals take less exercise in the course of finding food, and also domestically raised rodents have a much higher fat content than wild rodents.

Aruba Rattlesnakes are live bearing animals, with litters of up to 10 young being reported. Mating takes place in January or February, with young being born around 6 months later. Lifespan in captivity can be up to 20 years, but the lifespan in the wild is unknown. Natural predators are most probably other snakes and birds of prey, especially owls which are active when these nocturnal snakes are out looking for food or mates.

Although the Aruba Island Rattlesnake has been bred in captivity, the number of founder animals is low and there have been problems in recent years. Most captive animals (there were 175 worldwide in 2007) are in US zoos, but there are around 50 in European collections.



Next post: Mangrove Snake



(images from wikipedia)