- published: 13 Sep 2011
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The Seychelles giant tortoise (Aldabrachelys hololissa) has been thought to be extinct since the mid-19th century due to overexploitation on the granitic Seychelles islands. Similar giant tortoise species on other Indian Ocean islands such as Mauritius, Réunion and Rodrigues Island are also extinct. The only species of Indian Ocean giant tortoise to avoid this fate was the Aldabra giant tortoise due to its isolated location and 19th century conservation efforts.
This species inhabited islands of the Seychelles group, where it thrived on vegetation on the edges of marshes and streams. By 1840, it had disappeared from the wild and was assumed to be extinct. As a grazing species, it somewhat resembled the Aldabra tortoise with its domed shape.
In 1999, some Seychelles island tortoises (12 known individuals) were suggested to have survived in captivity. The report of oddly-shaped captive tortoises prompted the Nature Protection Trust of Seychelles to examine the identity of the living tortoises. Examination of museum specimens of the "extinct" Seychelles species by Dr. Justin Gerlach and Laura Canning seemed to show some living tortoises possess characteristics of the extinct species.
Seychelles (i/seɪˈʃɛlz/ say-SHELZ; French: [sɛʃɛl]), officially the Republic of Seychelles (French: République des Seychelles; Creole: Repiblik Sesel), is an island country spanning an archipelago of 115 islands in the Indian Ocean, some 1,500 kilometres (932 mi) east of mainland Africa, northeast of the island of Madagascar.
Other nearby island countries and territories include Zanzibar to the west, Mauritius, Rodrigues, Agalega and Réunion to the south, Comoros and Mayotte to the southwest. Seychelles, with an estimated population of 86,525, has the smallest population of any African state. It also has the highest Human Development Index in Africa.
Scholars assume that Austronesian seafarers, and later Maldivian and Arab traders were the first to visit the uninhabited Seychelles. Remains of Maldivian mariner presence from the 12th century were found in Silhouette Island. The earliest recorded sighting by Europeans took place in 1502 by the Portuguese Admiral Vasco da Gama, who passed through the Amirantes and named them after himself (islands of the Admiral).
Giant tortoises are characteristic reptiles of certain tropical islands. Often reaching enormous size—they can weigh as much as 300 kg (660 lbs) and can grow to be 1.3 m (4 ft) long—they live, or lived (some species are recently extinct), in the Seychelles, the Mascarenes and the Galapagos. Today, the world's largest population inhabits Aldabra Atoll in Seychelles, where there are approximately 150,000 individuals. Although appearing similar, the tortoises represent separate branches of evolution. The Seychelles and Mascarenes tortoises derive from nearby Madagascar, while the Galapagos tortoises came from nearby Ecuador.
Although often considered examples of island gigantism, prior to the arrival of Homo sapiens giant tortoises also occurred in non-island locales, as well as on a number of other, more accessible islands. During the Pleistocene, and mostly during the last 50,000 years, tortoises of the mainland of southern Asia (Colossochelys atlas), North and South America,Australia (Meiolania), Indonesia,Madagascar (Dipsochelys), and even the island of Malta became extinct. The giant tortoises formerly of Africa died out somewhat earlier, during the late Pliocene. While the timing of the disappearances of various extinct giant tortoise species seems to correlate with the arrival of humans, direct evidence for human involvement in these extinctions is usually lacking; however, such evidence has been obtained in the case of Meiolania damelipi in Vanatu.