Wednesday, February 4, 2009

Caribbean endangered species: reptiles extinction handbook.

It's Too Late

Reptile Extinctions

All but one reptile extinction have occurred on islands. At least 28 island reptiles have died out since 1600. A large number of reptile extinctions took place in the Mascarene Islands, a group of islands in the Indian Ocean, east of Madagascar (see Appendix for more on Mascarene Island extinctions). Thousands of large tortoises were slaughtered for food by European settlers and visiting ships' crews during the 17th century. All three Mascarene Islands and most of their satellite islets were densely populated by various species of tortoises. Each island had species with differently shaped shells: domed for feeding on low vegetation, and high‑fronted for other vegetation (Day 1981). Francois Leguat described Rodrigues' tortoises in the early 18th century: "There are such plenty of Land‑Turtles on this Isle that sometimes you see 2,000 to 3,000 of them in a Flock; so that you can go above a hundred paces on their backs without setting foot on the ground. They meet together in the evening in shady places and lie so close that one would think those spots were paved with them" (Day 1981). The large tortoises must have numbered in the hundreds of thousands, judging from the quantity taken by ships to provision their crews and to trade for commodities. Each weighed about 100 pounds, and naval ships vied with one another for rights to them. The tortoises were plundered indiscriminately. Far more were killed than needed by crews and passengers (Durrell 1977). One expert estimated that at least 10 thousand tortoises were taken per year from Rodrigues island alone. Many died en route, as in the case of one shipment of December 6, 1761, in which the ship “L'Oiseau” arrived with a cargo of only 3,800 tortoises still living out of the 5,000 shipped (Durrell 1977). The Mauritian tortoises were extinct by 1700, the two Reunion species by 1773, and the Rodrigues species in 1800 (Day 1981). The last of the tortoises were killed off by pigs consuming the young tortoises and rooting up their eggs in the sand (Day 1981). Eight tortoise species, including three giant tortoises, became extinct (see Table "Extinct Wildlife of the Mascarene Islands"). In all, 13 Mascarene reptile species disappeared forever. The blind cave snake and three skinks or geckoes also disappeared. The most recent extinction was the Round Island Boa, which inhabited an islet off the coast of Mauritius. Livestock and rabbits stripped the vegetation, which caused the extinction of this snake by 1975. No native tortoises or turtles still exist on the Mascarenes. The remaining species of boa and the four gecko and skink species are highly threatened, according to the 2000 IUCN Red List. Elsewhere in the world, reptiles have been eliminated mainly as a result of the combined effects of non-native species, such as rats, cats and mongooses. Predators prey and compete for habitat and vegetation, livestock overgraze and settlers destroy habitats. Nine species of iguanas and snakes of the Caribbean became extinct after introduced species of mongoose and rats demolished them. The iguanas were also hunted heavily for food by local people. A number of iguana species barely survive on various Caribbean islands, having become restricted to tiny islets off the main islands where rats, cats and livestock are not present. Four Caribbean reptiles have disappeared. A lizard (Ameiva major) and a snake (Dromicus cursor) were native to Martinique and became extinct in 1960 and 1962 respectively; the other two were native to Jamaica. A tree snake (Alsophis ater) was probably eliminated by forest destruction and predation by the introduced mongoose. The Jamaican iguana (Cyclura collei), thought to be extinct, was recently rediscovered, but the species is still highly endangered. The single reptile extinction on a mainland area was a South African lizard, Eastwood's longtailed seps (Tetradactylus eastwoodae) – it disappeared in 1913.

1 comment:

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