The
Galápagos tortoise (or
Galápagos giant tortoise), is the largest living
tortoise, endemic to nine islands of the
Galápagos archipelago. Adults of large subspecies can weigh over 300 kilograms (660lb) and measure 1.2&_160;meters (4&_160;ft) long.
Life expectancy of a wild tortoise is estimated to be 150-200 years.
[citation needed]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. When a tortoise feels threatened it can withdraw its head, neck and forelimbs into its shell for protection, presenting a thick shield to a would-be predator. The legs have hard scales that provide an effective armour when withdrawn.
The scutes of the carapace are not coincident with the underlying bony plates and grow at their outer edges. Tortoises thus keep their characteristic scute pattern throughout life. These do have annual growth bands but are not useful for telling the age as the outer layers are rubbed off in the normal wear and tear of living.
The shape of the carapace and other physical features correspond to the habitat of each of the 13 subspecies. Larger islands with more wet highlands such as Santa Cruz and Isabela (where the Alcedo Volcano is found) with lush vegetation near the ground have tortoises with 'dome-back' shells; these animals have restricted upward head movement due to shorter necks, and tend to have shorter limbs as well. These are the heaviest and largest of the subspecies.
