Seychelles giant tortoise
Encyclopedia
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.
However, recently published scientific papers on the genetics of the Seychelles and Indian Ocean tortoises provide conflicting results. Some studies suggest only one species was present historically, but others support the presence of three closely related species.
A 181-year old tortoise on Saint Helena
, named Jonathan
, is believed to be a survivor of the species (as well as being potentially the oldest living tortoise in the world presently).
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Extinction
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...
since the mid-19th century due to overexploitation
Overexploitation
Overexploitation, also called overharvesting, refers to harvesting a renewable resource to the point of diminishing returns. Sustained overexploitation can lead to the destruction of the resource...
on the granitic Seychelles
Seychelles
Seychelles , officially the Republic of Seychelles , is an island country spanning an archipelago of 115 islands in the Indian Ocean, some east of mainland Africa, northeast of the island of Madagascar....
islands. Similar giant tortoise species on other Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
islands such as Mauritius
Mauritius
Mauritius , officially the Republic of Mauritius is an island nation off the southeast coast of the African continent in the southwest Indian Ocean, about east of Madagascar...
, Réunion
Réunion
Réunion is a French island with a population of about 800,000 located in the Indian Ocean, east of Madagascar, about south west of Mauritius, the nearest island.Administratively, Réunion is one of the overseas departments of France...
and Rodrigues Island are also extinct. The only species of Indian Ocean giant tortoise to avoid this fate was the Aldabra giant tortoise
Aldabra Giant Tortoise
The Aldabra giant tortoise , from the islands of the Aldabra Atoll in the Seychelles, is one of the largest tortoises in the world....
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.
However, recently published scientific papers on the genetics of the Seychelles and Indian Ocean tortoises provide conflicting results. Some studies suggest only one species was present historically, but others support the presence of three closely related species.
A 181-year old tortoise on Saint Helena
Saint Helena
Saint Helena , named after St Helena of Constantinople, is an island of volcanic origin in the South Atlantic Ocean. It is part of the British overseas territory of Saint Helena, Ascension and Tristan da Cunha which also includes Ascension Island and the islands of Tristan da Cunha...
, named Jonathan
Jonathan (tortoise)
Jonathan is a Seychelles giant tortoise that lives on the island of Saint Helena.Jonathan was brought to the island from the Seychelles in 1882, along with three other tortoises at about 50 years of age. He was named in the 1930s by Governor Sir Spencer Davis...
, is believed to be a survivor of the species (as well as being potentially the oldest living tortoise in the world presently).