Turtles do not parent their young. After the female lays eggs, she leaves. Each young turtle must break out of the egg using a caruncle, a sharp piece of keratin (fingernail material) on its jaw. Hatchlings may not get to feed right away, so they rely on take-out food. The yolk sac attached to their bellies, containing leftovers from the egg, sustains them. Still, when a hatchling leaves the nest, its odds of survival are poor. Its shell is still soft, making it edible to lots of predators, and outside conditions are tough. Sea turtles must reach the ocean without being attacked by crabs or shorebirds. Freshwater turtles must travel long distances, sometimes over steep terrain, dodging foxes and raccoons. Land turtles like tortoises risk getting dried out before they find water. Some hatchlings stay in the nest through an entire winter, living off the yolk sac and emerging when the weather warms.