Koalas can sleep for about 18–20 hours a day, while little brown bats have clocked nearly 20 hours in laboratory studies. But the sloth’s sleepy reputation is less straightforward: wild sloths in one study slept for just under ten hours. Here are ten animals with very different ways of spending their downtime.
This countdown is a selection of notable sleepers, not a strict ranking by hours. We checked research papers, university summaries and zoo accounts; many figures come from small captive studies. Species, temperature and living conditions matter, and resting or drowsiness is not always the same as sleep.
| No. | Animal | Reported sleep per day | Where it lives |
|---|---|---|---|
| 1 | Koala | About 18–20 hours (zoo account) | Eastern and southeastern Australia |
| 2 | Sloth | About 9.6 hours wild; 15.9 captive (separate studies) | Central and South America |
| 3 | Brown bat | Up to about 20 hours (little brown bat; laboratory) | North America |
| 4 | Giant armadillo | About 18 hours (captive study) | South America |
| 5 | Python | About 16–20 hours (one captive African rock python) | Sub-Saharan Africa (study species) |
| 6 | North American opossum | About 18 hours (captive estimate) | North and Central America |
| 7 | Owl monkey | About 17 hours (captive study) | Central and South America |
| 8 | Tree shrew | About 16 hours including drowsiness; about 9 without | Southeast Asia |
| 9 | Hedgehog | About 10 hours (captive European hedgehogs) | Europe |
| 10 | Squirrel | About 14 hours (captive ground squirrels) | North America (study species) |
10. Squirrel
Captive thirteen-lined ground squirrels slept about 14 hours a day in laboratory studies. That figure does not directly describe gray squirrels like the one pictured, and no single total fits every squirrel species.
Gray squirrels are active during daylight, with much of their activity near the beginning and end of the day. They rest in tree cavities or leafy nests, rather than spending every daylight hour asleep. Their bushy tails are useful for more than balance: tail movements also help them communicate.
9. Hedgehog
About 10 hours of sleep per day was recorded in a laboratory study of European hedgehogs. Counting drowsiness as sleep produces a much larger total, which helps explain conflicting figures. The often-repeated 18-hour claim is not a dependable daily average for every hedgehog.
European hedgehogs usually forage at night and shelter in nests during the day, much like other nocturnal animals. They also hibernate when conditions demand it, but hibernation is a separate energy-saving state, not simply an extra-long nap. Their winter nests provide insulation while their body temperature and metabolism fall.
8. Tree Shrew
About 16 hours appears in older captive tree-shrew research, but that total includes drowsiness; excluding it gives about nine hours.
Tree shrews are small Southeast Asian mammals in the order Scandentia, not rodents. They are active by day and sleep mainly at night. A 2021 study found that their sleep was more consolidated than rats’ sleep, with some features resembling human sleep. Their name can be misleading: they are not true shrews either.
7. Owl Monkey
About 17 hours of daily sleep was reported for captive owl monkeys in early research. Also called night monkeys, these primates live across parts of Central and South America, from Panama to northern Argentina. That broad range covers several species, including the Panamanian night monkey shown here.
Most owl monkeys are active at night, although some southern populations also move about during daylight. They rest in tree hollows or dense vegetation. One surprising detail in the University of Wisconsin’s account: owl monkeys sometimes share sleeping trees with bats.
6. North American Opossum
About 18 hours per day is a published captive sleep estimate for the North American, or Virginia, opossum. Opossums are mainly active at night and spend daylight tucked into sheltered places such as hollow trees or brush piles.
Despite the familiar cartoon image, opossums do not sleep hanging from their tails. The tail helps with gripping and balance when climbing. This marsupial’s range stretches through much of North and Central America, and a sheltered den is a far more realistic sleeping place than a dangling branch.
5. Python
One captive African rock python slept about 16–20 hours a day, depending on whether it had been fed. With just one animal studied, treat that result as a curiosity rather than a rule.
The snake pictured is an African rock python (Python sebae). These large pythons often shelter among rocks or in mammal burrows and are frequently found near rivers and lakes. Adults are mainly active at night. They are among the largest living snakes.
4. Giant Armadillo
About 18 hours of daily sleep was reported for giant armadillos in captive research. These South American mammals are mainly nocturnal and spend much of the day underground.
Their powerful front claws make them effective diggers, both when excavating burrows and when opening termite nests. A giant armadillo can even balance on its hind legs and tail while digging. During the day, the burrow provides shelter while this elusive animal stays out of sight.
3. Brown Bat
Nearly 20 hours of daily sleep has been recorded in captive little brown bats. Other laboratory temperatures produced shorter totals, so “20 hours” is not a year-round rule. This North American insect-eater hunts at night and uses sheltered roosts during the day.
Winter hibernation is different from ordinary daily sleep: metabolism and heart rate drop to conserve energy. The Missouri Department of Conservation reports that little brown bats can gain about 30% in body weight before hibernation. When active, they locate flying insects through echolocation, listening for the returning echoes of their calls.
2. Sloth
About 9.6 hours per day was measured in three wild brown-throated three-toed sloths in Panama. An earlier captive study reported about 15.9 hours. The 2008 wild-sloth study showed why observations from captivity should not automatically be treated as a wild animal’s routine; the groups also differed in age.
Sloths inhabit forests in Central and South America and spend much of their time in the trees. Their unhurried movement makes them famous among the world’s slowest animals, but moving slowly is not the same as being asleep. Researchers used miniature brain-recording equipment to distinguish sleep from wakefulness in the wild study.
1. Koala
About 18–20 hours of daily sleep is the range given by Zoos Victoria. Koalas live in eastern and southeastern Australia, including New South Wales as well as Queensland, Victoria and South Australia. Their eucalyptus diet supplies relatively little energy, and long periods of rest help keep their energy needs low.
Koalas sleep supported by tree branches and trunks, then wake to feed on selected leaves. Among these distinctive Australian animals, the hands are a useful detail to notice: each front paw has two opposable digits that help grip branches.
