Ages 6 to 12 years. Hibernation is one of nature's greatest miracles, allowing animals to sleep through periods of extreme cold (and heat). From the tundra to the desert, this ability enables animals to live in some of Earth's harshest climates. Full-colour photographs and vivid text combine to give children a view of the many different ways that animals "sleep it off". Highlights include: how an animal's body uses fat to survive and even wake itself up; how an animal finds and prepares its den for hibernation; animals that estivate, or hibernate to escape heat; animals that give birth and care for their young during hibernation.