Tortoises need to drink fresh water at least once a week to survive. On Aldabra Island in the Indian Ocean, giant tortoises drink from pools and sit in them to cool down. But as the dry season progresses, the pools get smaller and more crowded, and the weaker tortoises can become mired in the mud and die of starvation. And yet there are 150,000 tortoises on the atoll. They eat mainly vegetation, cropping the grass down to the rootstock. But like many island animals, their diet has broadened and they will even feed on the carcasses of their dead companions since the flesh is too nutritious to waste in this barren land.