'Extinct' Giant Tortoises Rediscovered
The survival of 'extinct' giant tortoises from the granitic islands of Seychelles was confirmed by the Nature Protection Trust of Seychelles in 1997. Giant tortoises were common on all islands in the western Indian Ocean until Mauritius was colonised in the 1600s when increasing numbers of explorers and settlers visited the Seychelles islands and removed or killed the tortoises in vast numbers. By 1840 the only surviving giant tortoises in the wild were those on the inhospitable Aldabra atoll some 700 miles away and the unrelated Galapagos giant tortoises in the Pacific. Even on these islands extinction was only narrowly avoided. In the Indian Ocean the Aldabran tortoises were saved by appeals for the conservation of Aldabra by eminent scientists of the time, including Charles Darwin, and the leasing of the island by Lord Walter Rothschild who maintained a passionate interest in the biology and conservation of these animals.
It has generally been assumed that only the Aldabran species survived this over-exploitation. Occasionally, most recently in 1995, it has been suggested that some Seychelles granitic island tortoises survive 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 confirmed that some living tortoises do show characteristics of the supposedly extinct species. A discussion of the identification of these tortoises and controversies surrounding their origins are discussed on other pages.
These species, thought to have been driven to extinction 120 years ago, were the subject of a highly successful conservation programme by the Nature Protection Trust of Seychelles.
Other pages provide more information on the captive breeding programme and reintroductions and profiles of the captive tortoises. The biology and conservation of Indian Ocean giant tortoises is described in detail in 'Giant Tortoises of the Indian Ocean' by Justin Gerlach.
Sir David Attenborough is the patron of this conservation project
|Sir David Attenborough with Justin Gerlach|
Living Indian Ocean giant tortoises:
Aldabra giant tortoise - Dipsochelys dussumieri
This species is often known as Geochelone gigantea orDipsochelys elephantina but should, more correctly, be calledDipsochelys dussumieri. It is naturally restricted to Aldabraatoll, and possibly the nearby atolls, although it has been introduced toseveral of the granitic Seychelles islands. Some 100,000 wild tortoiseslive on Aldabra.
It is a domed species adapted to grazing on the low grass and herbs of theatoll.
Seychelles giant tortoise - Dipsochelys hololissa
This species inhabited the granitic islands of the Seychellesgroup where it grazed the vegetation on the edges of marshes and streams. By 1840 it had disappeared from the wild and was assumed to be extinct. In 1997 8 captive survivors were recognised in Seychelles. Thesewere included in the NPTS Seychelles Giant Tortoise Conservation Project. Since then other survivors have been found in zoos elsewhere in theworld. Only 12 adults are known.
As a grazing species, it superficially resembles the Aldabran tortoise inits domed shape but is distinct on close examination.
Arnold's giant tortoise - Dipsochelys arnoldi
Alsoknown as the Seychelles saddle-backed tortoise. This species also inhabitedthe granitic Seychelles islands until 1840. Captive tortoises wererecognised in 1997 and were part of the NPTS Seychelles Giant TortoiseConservation Project. Only 18 adults are known.
This species is adapted to browsing, it has a flattened 'saddle-backed' shell and unique jaw and leg modifications to enable it to browse efficiently. The 'saddle-backed' shape is most developed in some Galapagos tortoises where it is involved in browsing and in ritual combats. Such combats are not known in Seychelles tortoises and the 'saddle-backed' shell is less extreme.
The different species were described in detail in the journal of the Freshwater Turtle and Tortoise Specialist Group - Chelonian Conservation & Biology 3(1) in August 1998. The feeding behaviour of the tortoises is described in issue 3(3) of December 1999.