The sample size was small—and so were the findings. Researchers asked the question "Does large body size make elephants the shortest mammalian sleepers?" and sought to answer it in the wild, in a departure from most previous related research, which involved elephants in captivity. After tracking two wild African elephant matriarchs in Botswana's Chobe National Park for 35 days, they found the creatures averaged just two hours of sleep daily, "the shortest ... of any mammal recorded to date." The study, published Wednesday in PLOS ONE, describes elephants as "polyphasic" sleepers, meaning they sleep multiple times a day, though most of their sleep occurred between 2am and 6am. As for the quality of that sleep, oof: Elephants slept in a recumbent position only every three or four days, with the other sleep occurring in a standing position.
That "potentially limit[s] their ability to enter REM sleep on a daily basis," per the researchers. And on five occasions, the elephants were tracked as being awake for as many as 46 consecutive hours and "exhibited no form of sleep rebound following a night without sleep." The amount of sleep they got had no correlation with their amount of daily activity; they were tracked traveling as many as 19 miles in 10 hours, "possibly due to disturbances such as potential predation or poaching." Mashable notes that previous studies have pegged the sleep time for elephants in captivity at 3 to 7 hours, and lead author Paul Manger says the quest for food is probably the differentiator. "As we build up more information, the ideas for conservation will become stronger and guided by real data—and not just people's gut feelings," he says. (Read more discoveries stories.)