Bats are the world's longest-sleeping mammals, with the little brown bat averaging 19.9 hours of sleep a day, according to data published by Savage and West in the Proceedings of the National Academy of Sciences (PNAS).
The big brown bat follows closely at 19.7 hours, while the thick-tailed opossum sleeps 19.4 hours daily.
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Other heavy sleepers include the giant armadillo, North American opossum, owl monkey and Arctic ground squirrel.
The tiger rounds out the top 10, sleeping an average of 15.8 hours each day. Researchers note that mammals with less exposed sleeping sites tend to sleep longer.
