Which mammal spends the most time sleeping?

The western European hedgehog—which likes to live in hedges—spends most of its life asleep. It builds a nest of grass and leaves among tree roots or under a bush, and spends about 18 hours a day there during summer months. It wakes up at night to eat, sniffing out worms, insects, snails, and snakes for its evening meal. During the winter months, it hibernates (sleeps all the time). When it sleeps or senses danger, the hedgehog rolls into a tight, spiny ball for protection. Related creatures, including sloths, armadillos, and opossums, sleep almost as long as the hedgehog—accumulating up to 17 hours each day! Other animals that sleep a lot are the dormouse (about 17 hours), koalas (about 15 hours), and all kinds of felines, including pet cats.