They are the giants of the animal kingdom – but new research has found that elephants get by on a tiny amount of sleep. African elephants sleep an average of just two hours a day in the wild and regularly go nearly two days without sleep, according to the study.
African elephants are the largest land animal, and evidence suggests that larger mammals tend to sleep less.
But many studies on elephant sleep have been done in a captive setting only – or were unable to accurately distinguish rest from sleep.
To study in more detail how elephants sleep in the wild, researchers monitored two free-roaming African elephant matriarchs in Chobe National Park, Botswana, for 35 days.
The researchers fitted the elephants with an electronic monitoring device implanted in the trunk to track sleep accurately.
They also used a collar with a gyroscope to track sleeping position.
They found that the elephants slept an average of two hours a day, which is the shortest known sleep time of any land mammal.
On several days during the study, the elephants went without sleep for up to 46 hours and travelled long distances of around 30 kms (18.6 miles) during these periods, possibly due to disturbances such as lions or poachers.
And the elephants slept lying down only every few nights.
The researchers said this could limit their potential for daily rapid eye movement (REM) sleep, raising questions about how frequently elephants experience the kind of sleep required for dreaming.
While only two elephants were tracked, the researchers say their findings provide new insights into the sleep patterns of elephants in the wild.
Study leader Professor Paul Manger, of University of the Witwatersrand in South Africa, said: ‘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.
‘In addition, it appears that elephants only go into REM, or dreaming, sleep every three to four days, which makes elephant sleep unique.’
The findings were published in the journal PLOS ONE.
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