The gentle giant
The Galápagos tortoise (or Galápagos giant tortoise), is the largest living tortoise, endemic to 9 islands of the Galápagos archipelago. The shape of the carapace of some species of the tortoises reminded the Spanish explorers of a 'galápago' saddle and it was after these saddle-shaped tortoises that they named the archipelago.
Among the 14 sub-species found on the various islands there is a great variation in shell shape and size. It is thought that 3 of these sub-species are now extinct.
Adults of large species can weigh over 300 kg and measure 1.2 m (4ft) long. Although the maximum life expectancy of a wild tortoise is unknown, the average life expectancy is estimated to be 100 years.
The Galápagos tortoises have very large shells (carapace) made of bone which is an integral part of the skeleton. The bony plates of the shell are fused with the ribs and other bones to form a rigid protective structure. Mating appears to occur at any time of the year although it does have seasonal peaks. Almost any kind of green vegetation is taken as food, including Hippomane mancinella which is highly poisonous to most creatures.
When possible the Galapagos tortoise spends long periods of time partially submerged in muddy pools. At night it may dig itself into soft ground or vegetation.
It was the giant tortoise that tipped Darwin off to the incredible diversity of the Galapagos fauna and flora. The giant tortoise is the symbol of both the Charles Darwin Research Station and the Galapagos National Park Service.
In the form of one particular individual, Lonesome George, the sole surviving member of the Pinta Island race, the giant tortoise is the symbol of extreme fragility of the Galapagos islands, and a reminder of the need for vigilance and conservation.
This species is of great historical scientific interest since, by illustrating a correlation between geographic isolation and morphological divergence, it was instrumental in the formation of Darwin's concept of evolution through natural selection.
Your chances of seeing one in the wild
Around 250,000 tortoises are thought to have lived on Galapagos before the arrival of humans. Today only 15,000-20,000 survive. Of these, about 3,000 live on Volcan Alcedo. Geochelone elephantopus is listed on Appendix I of CITES.
They are strictly protected in the Galapagos, which were declared a National Park in 1959. Significant captive breeding and rearing projects are being carried out at the Charles Darwin Research Station. However, the tortoises continue to face threats from introduced species such as rats, and habitat destruction.