They are also the world's largest tortoises, with some specimens exceeding 5 feet (1.5 meters) in length and reaching 550 pounds (250 kilograms). There are now only 11 types of giant tortoises left in the Galápagos, down from 15 when Darwin arrived. Hunted as food by pirates, whalers, and merchantmen during the 17th, 18th, and 19th centuries, more than 100,000 tortoises are estimated to have been killed off. Nonnative species such as feral pigs, dogs, cats, rats, goats, and cattle are a continuing threat to their food supply and eggs. Today, only about 15,000 remain.
The tortoises are now listed as endangered and have been strictly protected by the Ecuadorian government since 1970. Captive breeding efforts by the Charles Darwin Research Station are also having positive effects. Galápagos tortoises lead an uncomplicated life, grazing on grass, leaves, and cactus, basking in the sun, and napping nearly 16 hours per day. A slow metabolism and large internal stores of water mean they can survive up to a year without eating or drinking.
The top shell of a tortoise is called the carapace; the shell that covers a tortoise's belly is called the plastron. The populations of Galápagos tortoises that live on the hotter and drier islands of the Galápagos have developed shells that are saddle-shaped with a high notch above the neck. This allows them to stretch their necks higher to reach vegetation that grows above the ground.
Tortoises lay eggs. Females lay their eggs in nest holes, which they cover and leave. Babies hatch in four to eight months. They are on their own from the beginning.