African elephants in the wild sleep for just two hours a day, recording the shortest daily sleep time, among mammals.
With African elephants being the largest land mammals, the new research suggests that bigger mammals need the least sleep. The elephants in the wild had an average daily sleep time of two hours, often going without sleep for up to two days.
Researchers at the University of the Witwatersrand, South Africa, tracked two free-roaming matriarch African elephants in their natural habitat in Chobe National Park, Botswana.
The elephants were monitored using an actiwatch implanted in the trunk and a collar fitted with GPS and gyroscope, to track sleeping habits and positions.
The team found that the average daily sleep duration of the elephants was two hours. They also noted that on many occasions, the elephants went without sleep for upto 46 hours and traveled around 30km, due to disturbances such as threats from predators, poachers, or a bull elephant.
The elephants were observed to sleep while standing, lying down every third or fourth night. They experienced rapid eye movement (REM) sleep for 10 out of 35 days of tracking, when they slept lying down.
“Studies of sleep in captive elephants have shown that they sleep for four to six hours per day. However, the current study shows that in their natural habitat, wild, free-ranging elephants sleep only for two hours per day, the least amount of sleep of any mammal studied to date, but this appears to be related to their large body size,” said Paul Manger, University of the Witwatersrand.
“In addition, it appears that elephants only go into REM, or dreaming, sleep every three to four days, which makes elephant sleep unique,” added Manger.
The findings have been published in the journal PLOS ONE.
