They may have round ears and long tails, but dormice are not members of the same family as regular mice, Muridae. Instead, they belong to the family Gliridae who share a suborder with squirrels and beavers. The primary difference between dormice and common mice – the kind that you might find in your home is that the former has a fluffy tail while the latter's is scaly.
Dormice that live in temperate climates go through long periods of hibernation lasting six months or more. They make their nests along the forest floor, hidden by logs and piles of leaves. Sometimes they'll use an abandoned bird's nest or build their own nest with bark and leaves. They like to hibernate at the base of well-established hedgerows. Although they may wake up during a particularly lengthy sleep to get a snack, the animals usually try to eat enough food to fatten up before hibernation begins.
The name dormouse is thought to stem from the French word "dormir," which means to sleep. The second element, "mouse," is commonly thought to be in relation to its species. However, it more likely comes from the feminine version of "dormir" ("sleeper"), which is "dormeuse,".
Dormice vary greatly in size. For instance, an edible dormouse (found in Western Europe) can be more than twice as long as a Japanese dormouse. At their largest, they can reach 8 inches in length, but the smallest ones are as little as 2 inches long. They can weigh between .5 ounces (that's less than a slice of bread) and 6.5 ounces.
With their long, grasping toes and sharp claws, dormice are said to be some of the most acrobatic arboreal (tree dwelling) animals. They may be tiny, but their ability to scurry up trees and twigs comes in handy when they're trying to avoid predators, such as foxes and weasels, or reach a dangling berry. These claws give the creatures an advantage when it comes to digging, too.
The tiny dormice of today hail from giant dormice, an extinct ancestor (as big as a rat) from the Pleistocene. Fossils date back to the early Eocene epoch, a period of 33 to 56 million years ago, when they are thought to have lived alongside ancient horses, primates, and bats. They were discovered in Europe and Asia at least 30 million years before being discovered in Africa.