Mary Lindeen 
Frozen Frogs and Other Amazing Hibernators [PDF ebook] 

When it gets colder during the winter, we can go inside and turn up the heat. But what do animals that live outside do? Some of them survive the winter by hibernating. These animals manage to stay alive by slowing down their heart rates, curling up tight in their shells, or even freezing themselves! Read this book to learn more about the amazing animals that hibernate.