Giant tortoise
This may occur due to factors such as relaxed predation pressure, competitive release, or as an adaptation to increased environmental fluctuations on islands.
Giant tortoises were formerly common (prior to the Quaternary extinctions) across the Cenozoic faunas of Eurasia, Africa and the Americas.
However, extinct giant horned turtles (Meiolaniidae) likely filled a similar niche, with Late Pleistocene-Holocene meiolaniid species being known from Australia, New Caledonia, Lord Howe Island, Vanuatu, and the Fijian Archipelago.
The identity of the Vanuatu meiolaniid has been controversial, however, with some studies concluding the remains actually belong to a giant tortoise, which are otherwise unknown from this region.
[11][12] One interesting relic is the shell of an extinct giant tortoise found in a submerged sinkhole in Florida with a wooden spear piercing through it, carbon dated to 12,000 years ago.
[13][better source needed] Today, only one of the subspecies of the Indian Ocean survives in the wild; the Aldabra giant tortoise[1] (two more are claimed to exist in captive or re-released populations, but some[vague] genetic studies have cast doubt on the validity of these as separate species)[citation needed] and 10 extant species in the Galápagos.
[15] On 23 March 2006, an Aldabra giant tortoise named Adwaita died at the Alipore Zoological Gardens in Kolkata.
[citation needed] Giant tortoises are now protected by strict conservation laws and are categorized as threatened species.
[16][better source needed] Aldabra giant tortoises tend to spend their lives grazing, but will cover surprising distances in search of food and have also been observed on bare rock and thin soil.
Scientists believe the first tortoises arrived to the Galápagos 2–3 million years ago by drifting 600 miles from the South American coast on vegetation rafts or on their own.
These buccaneers stocked giant tortoises not only because of their meat but because of these animals' ability to survive for six months to one year without food or water.
[citation needed] Once buccaneers, whalers and fur sealers discovered that they could have fresh meat for their long voyages by storing live giant tortoises in the holds of their ships, massive exploitation of the species began.
[25][better source needed] Galápagos tortoises are mainly herbivorous, feeding primarily on cactus pads, grasses, and native fruit but have been recorded eating baby birds in the case of the aldabran species.
In the hot season, their active period is early morning and late afternoon, while midday finds them resting and trying to keep cool under the shade of a bush or half-submerged in muddy wallows.
During the cool season (June to November), female tortoises migrate to nesting zones, which are generally located in low lands of the islands, to lay their eggs.
They differed from any other giant tortoise species because of their modified jaws, reduced scales on the legs and shells averaging just 1mm thick.
[17][28] Around the 16th century, with human arrival and the subsequent introduction of domestic animals, particularly pigs, the tortoises were hunted to extinction.
[citation needed] The thin shells were of no protection against these new invaders; rats, cats and pigs devoured the eggs and young and thousands were collected alive for provisioning ships.
[29] Today, the only remains from these five species are a number of fossil bones and shells, a few drawings of live animals and one stuffed Rodrigues saddle-backed giant tortoise in France's National Museum of Natural History.
