Five eggs the size of Ping-Pong balls crack open as the tiny desert tortoises inside break through the shells. The two-inch-long babies immediately crawl off in search of flowers and grasses to eat.

Galápagos tortoises can live to be over a hundred years old. 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 ...