The small rodent often said to “sleep like a” dormouse is the dormouse. The expression reflects the animal’s unusually long periods of inactivity and its name, which is associated with sleep or dormancy. Dormice belong to the rodent family Gliridae and are found across parts of Europe, Asia, and Africa.
Many temperate dormice hibernate for about six months or longer. During warmer months, they feed on foods such as berries, fruit, flowers, insects, and nuts, while also building fat reserves. When winter arrives, their metabolism, body temperature, breathing, and heart rate fall sharply, conserving energy when food is scarce. Some species also store food nearby and wake briefly during winter to eat.
The dormouse is not simply an unusually sleepy mouse. Most dormice are nocturnal, often climbing trees and using hollows or nests during the day. The phrase “sleep like a dormouse” is also distinct from “sleep like a log”: it points to a real animal famous for prolonged dormancy, not merely deep everyday sleep.