Those funny-looking tortoise legs might not be made to walk fast, but they sure can dig. A single tortoise can have as many as 35 burrows. Some of these may be shallow holes, but others designed for winter survival can have tunnels as long as 30 feet. These burrows are skillfully constructed to remain at a steady temperature and keep out water.
Every creature needs a place to live, even one who carries a shelter on his back. As a cold-blooded reptile, a tortoise uses his burrows to keep warm in the winter and cool in the summer. A tortoise will build several burrows, facing different directions and in different locations so that he will always have at least one that can keep his body the right temperature. For example, north-facing burrows stay cooler, while south-facing burrows tend to stay warmer.
Despite winning a race against the hare in fables, a tortoise can't outrun his predators. A burrow provides a safe place for him to hide from birds of prey, coyotes, foxes, cats, wild pigs, dogs, roadrunners and other animals looking for a tasty snack. Keeping several active burrows ensures that one will be nearby when he needs it.
Tortoises hibernate during winter months, which means they need a safe, warm and dry place to literally "hole up" in until spring. A burrow meets all these requirements. He doesn't have to worry about predators catching him sleeping, the underground space stays warm enough to keep him from freezing to death, and runoff from rain and snow doesn't flow into a properly built burrow.
A female tortoise doesn't always nest inside a burrow, but she will often lay her eggs near the entrance or within the nearby vicinity. Some tortoises do, however, build a nest deep within a borrow or in the tunnel leading to it. Since a female tortoise will often have more than one nest or clutch of eggs, she may use several different burrows for nesting.