by Karen Ellis

Created on: July 07, 2008

Can you imagine living 150 to 200 years as the giant Galapagos tortoise. These are the largest tortoises in the world and they weigh up to 660 pounds and four feet in length. Originally there were thirteen subspecies of this tortoise (Geochelone nigra) living on the Galapagos Islands.

Today the numbers of this huge reptile have been reduced to eleven subspecies. Five of the subspecies live on Isabela Island with the other six divided between the other islands. Lonesome George is the only known surviving male of the Pinta subspecies, therefore they are expected to become extinct shortly. There is great hope that there may be males other than George roaming about without scientific knowledge.

Appearance

Of course, the most noticeable part of the giant Galapagos tortoise is his huge shell which is made of bone. This shell or carapace is fused to the tortoises ribs and other bones forming his protective home. Any predator would have a tough time getting at this tortoise when he brings his legs and head into his shell.

The tortoise's scute, external plates on the carapace (shell), is divided into three parts, the central, the coastal and the marginal. They keep the scute pattern for all of their life. Although, there are growth bands, these are difficult to discern the age of the tortoise as they wear out and are rubbed off.

The giant Galapagos tortoises appearance differ depending from which island they reside.
On the larger Islands of Santa Cruz and Isabela where the highlands are wetter and there is thick vegetation close to the ground, the tortoise carapace is more of a dome shape. They also have shorter necks and limbs, yet they are the largest of the island tortoises. However, the tortoises near the Sierra Negra volcano on the southern end of the Isabela Island has a "table top" shell that is flat on top.

In Espanola and Pinta, dryer islands, the carapace is higher over the neck and flared out over the back feet. Called saddleback tortoises, they have longer, thinner limbs most likely to reach the higher vegetation of this area. They are smaller with males averaging a weight of 119 pounds, and females 60 pounds.

In all species, the male has a concave undershell, making mating an easier process. And all of them keep the dull brown color shell and scales on their necks and legs without much variation.

Location

The Galapagos Islands are located west of Ecuador in South America. This is the natural habitat of the giant Galapagos tortoise. The island was named after

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