The dormouse looks like a squirrel. It has a small head, 8.5 cm to 12 cm in length, and weighs only 30 to 100 g. It has a tail that is about the same length as the body. In the name of snooze, the dormouse sleeps most of the year and hibernates for up to 9 months. It is the longest hibernating animal in the world. It is because they sleep too long that they often die because of hunger during a long sleep.