Which Animal Sleeps the Most?

Among well-studied animals, koalas are among the longest sleepers, resting up to 18-22 hours per day. Their eucalyptus-leaf diet is low in nutrients and calories and high in toxins, requiring extensive digestion and minimal energy expenditure. The little brown bat and the big brown bat sleep about 19-20 hours, conserving energy between nocturnal feeding flights. The giant armadillo sleeps roughly 18 hours. By contrast, giraffes sleep as little as 30 minutes per day in the wild (in short naps of 1-2 minutes), and elephants sleep about 2-4 hours. Sleep duration generally correlates inversely with body size and predation risk.