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· Article

The Sleepiest Animals

· Article

The Sleepiest Animals

When we think of sleepy animals, sloths often come to mind.


In captivity, sloths log anywhere from 15 to 20 hours of snoozing every day. But in the wild, sloths actually only need about 9 hours, and are far from the sleepiest critters in the animal kingdom. So who are the sleepiest?



House cats rank among the sleepiest animals, averaging at least 12 hours a day. Some cats, according to, can average between 15 and 20 hours — twice as much as the typical wild sloth. Scientists think it’s because domesticated cats retain some of the characteristics of their wild counterparts, using the day to sleep and hunting during the night when prey is easier to catch. Hunting for prey, such as chasing mice around the house, expends an enormous amount of energy, so cats are known for taking brief periods of rest even during their waking hours. Hence, a “cat nap.”



These amphibians also average an impressive amount of sleep. Not only do they hibernate during cold months, but they spend most days asleep even during hot weather, burrowing underground to keep the sun from drying out their skin. During warm nights, however, toads get busy — night hours are prime time for toads to hunt insects, lay eggs and find a mate.



According to some sleep scientists, carnivores and omnivores tend to sleep for longer periods than herbivores, possibly because the protein in meat keeps them fuller longer, and they’re less likely to need to stay awake and scrounge for additional food sources. It makes sense, then, that carnivores top the list of some of the sleepiest animals. At 18 hours of sleep per day, North American opossums are at the top. Diurnal sleepers, North American opossums are notorious for sleeping all day and feeding on carrion (like road kill) during the night.


And the winner is …

sleepy_animals_3So who is the sleepiest in the animal kingdom? The winner is the brown bat, a North American native that logs 19.9 hours of sleep daily. Like toads, brown bats hibernate during winter months and emerge only at night for a few hours in warm weather to hunt insects. According to Jerome Siegel, director of UCLA’s Center for Sleep Research, brown bats sleep the most because they eat mostly mosquitoes, which are available for only four hours in a 24-hour cycle.


“If [brown bats] were flying around the rest of the day, they would be wasting energy with no beneficial effect on their genetic survival,” says Siegel. “Evolution selects for efficiency.”



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