Elephants spend less time dreaming than we thought, opting for short power naps in the middle of the night instead. The reason why animals sleep is one of life’s biggest mysteries, and by observing the slumbering habits of the African giants, some of our biggest assumptions are being challenged.
Researchers at the University of Witwatersrand in Johannesburg used Fitbits to track two matriarch elephants living in Chobe National Park in Botswana. They attached the trackers to their trunks, which only lie still when elephants sleep, to find out how much time the animals spent sleeping, and at what times of day.
In particular, the team wanted to find out how much time the elephants spent in REM, or ‘Rapid Eye Movement’ sleep. Many animals spend time in REM, and it’s believed to be the state of deep slumber where dreams take place. The reason why REM occurs is still a mystery, but many sleep scientists believe it has something to do with long-term memories being solidified in the brain. REM only occurs in elephants when they lie down to sleep, which the scientists tracked using gyroscopes around the animals’ necks.
To their surprise, the two female elephants only spent around an hour in REM sleep every three to four days. “Our findings are not consistent with the hypothesis of the function of REM sleep, as the elephant has well-documented long-term memories, but does not need REM sleep every day to form these memories,” says Professor Paul Manger, from Wits University.
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Other surprises lay in the times of day that the elephants chose to nap. Spending around two hours standing up in non-REM sleep per day, the two matriarchs mainly slept in the small hours, waking up well before dawn. “The data also indicates that environmental conditions (temperature and humidity, but not sunlight) are related to when the elephants fell asleep and when they woke up,” adds Manger.
Finally, the elephants were willing to sacrifice sleep to say safe from poachers, predators, and other testosterone-fuelled bull elephants. The two females could spend up to two days without any sleep if they needed to lead their herds far away from danger.
The research highlights how little we understand about the state that we humans spend a third of our lives in. But more studies like this will continue to unlock this mystery, which could help to improve our lives, and to better understand other animals.
“Understanding how different animals sleep…helps us to understand the animals themselves and discover new information what may aid…conservation strategies,” concludes Manger. “(It also) helps us to understand how humans sleep, why we do, and how we might get a better night’s sleep”.
The study was published in the journal PLOS ONE.