Giant tortoises spend most of their time eating grass, cacti and leaves. They move slowly and steadily across the island, and can go for a very long time without food or fresh water because their bodies are very good at storing both. Sailors in the past even used to take tortoises on ships as a supply of fresh food for long voyages — the tortoises could survive for months without being fed.
Different islands in the Galápagos have tortoises with different shell shapes. Tortoises on islands with tall cacti have long necks and saddle-shaped shells that let them reach up high. Tortoises on islands with plenty of low grass have dome-shaped shells and shorter necks. This is another example of the adaptation Charles Darwin observed on his visit.
Giant tortoises love to wallow in muddy pools and streams. This keeps them cool in the hot island sun and may also help get rid of ticks and other insects that bother them. At night, they tuck their heads and legs inside their shells to stay warm.
The Galápagos tortoise population dropped dangerously low in past centuries due to hunting and the introduction of animals like goats and rats to the islands. Today, a major conservation programme breeds tortoises in captivity and releases young ones back onto the islands. Numbers are now recovering, and Española Island — which once had only 15 tortoises left — now has over 2,000.