Galapagos Giant Tortoise
Tagged: animal, animals, bird, cat, dogGeochelone nigra
Before permanent settlers arrived on the Galapagos Islands in the 1830s, there were huge numbers of giant tortoises. Since then habitat destruction and immigrant predators have taken their toll. Lying off the coast of Ecuador and almost on the equator, the Galapagos Islands achieved lasting fame after the English naturalist Charles Darwin published his theory of evolution in The Origin of Species (1859). The book was written after his visit to the islands in 1835. The area was already well known to whalers and other seamen who, between 1789 and 1860, took tortoises to keep on their ships as sources of fresh meat. The tortoises, with water stored in their bladders, would survive on the ships for several months until they were needed. Whaling declined after 1860, when petroleum started to be used instead of whale oil for lighting. Apart from humans, the tortoises had no predators except some birds, which took hatchlings. Galapagos tortoises are the largest in the world. One male specimen measured 4.3 feet (1.3 m) and weighed about 425 pounds (200 kg). There is considerable variation in the shape of the shell, depending on which island they inhabit, a phenomenon that was noted by Darwin and helped form his theories.
Some tortoises have domed shells; others have “saddleback” shells that allow the head to be raised higher. The length of the neck and size of the head also vary; they were considered to be a single species, but scientific study showed that there were 15 different “races” from the various islands, and each one has a third name to distinguish it from others. Three races are now extinct, and some of the others are very rare. When settlers came to the islands in the 1830s, they brought pigs, goats, dogs, cattle, and burros (donkeys), some of which escaped and began to breed, causing a further decline in tortoise numbers. Pigs and dogs eat eggs and hatchlings; the other animals destroy the vegetation and trample tortoise nests. Rats and fire ants, both introduced species, also eat large numbers of hatchlings. In 1928 a New York Zoological Society expedition collected 180 tortoises and allocated them to zoos as far away as Australia. Some of them have bred to second generation, and one from San Diego zoo was returned to the islands for a captive-breeding program. Following pressure from scientists, the Charles Darwin Foundation was formed in 1959, followed in 1964 by the Charles Darwin Research Station. The islands became a national park, and laws were passed to prevent the removal of any animals.
Long-Term Plans It is estimated that some islands may need 100 years to recover their vegetation and tortoise populations. The recovery program instituted by the research station has included collecting eggs from the wild and incubating them artificially, and removing introduced animals. The first young were released in 1970. Collecting eggs in the wild for incubation has progressed to breeding some tortoises at the research station. The first hatchlings were released in 1975, and in 1991 the first wild-bred hatchling was found on the island. The highlight of the program was the release, early in 2000, of the thousandth tortoise on Espanola.
The tortoise population of the islands has almost doubled in recent years, and laws have been passed to restrict settlement and protect the coastal waters. Quarantine laws forbid the introduction of nonnative plants and animals. One problem was that some of the races had been reduced to very low numbers, and their lack of genetic diversity was a cause for concern. Even today it is possible that more tortoises may be found on islands where populations are low. This would seem to be the only hope for a tortoise nicknamed Lonesome George, the sole survivor of a race from Pinta Island. He was discovered in 1971 and moved to the station with two females of another race, but as yet no eggs have been produced, and no Pinta female can be found. Galapagos giant tortoises are now rare or extinct on many of the islands because of habitat destruction and the introduction of animals thatprey on the young or compete with adults for food.
Statistics: Galapagos giant tortoise Geochelone nigra
- Diet: Almost any green vegetation
- Family: Testudinidae
- World population: About 10,000
- Breeding: About 7-20 eggs buried in soil
- Distribution: Galapagos Islands, Pacific Ocean
- Habitat: Volcanic islands; hot and dry with rocky outcrops; some forested areas with grassy patches
- Size: Length: up to 4 ft (1.2 m). Weight: up to 500 (b (227 kg)
- Form: Huge tortoise with gray-brown shell and hardÂscaled legs; some have domed shells; others are saddleback (resembling a saddle in shape)
- Related endangered species: All subspecies of Geochelone nigra are on the IUCN Red List, including the Abingdon Island tortoise (Geochelone nigra abingdoni) EW; Duncan Island tortoise (G. n. ephippium) EW; Charles Island tortoise (G. n. galapagoensis) EX; Hood Island tortoise (G, n. hoodersis) CR. The Brazilian giant tortoise (G. denticulata) is VU
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