Giant tortoises are naturally buoyant, so if one on the African coast was swept out to sea it could have survived the journey to islands in the Indian Ocean like Aldabra. But Aldabra is a very harsh place to live. The coral rock that forms the substance of the island is easily eroded into sharp edges that can easily cut the feet of any animal travelling over it. Occasionally the rock forms deep pits into which tortoises sometimes fall and starve to death. The island is extremely hot and some tortoises die by being baked alive in their shells, leaving empty shells scattered over the island. So, in the heat of the day, they head for the shade of the low windswept guettarda trees and gather underneath them before returning to search for more edible leaves.