Elephants are insomniacs, sleeping just 2 hours a night

Bigger mammals generally need less sleep, and new research shows that African elephants ― the biggest land mammals of all ― need the least sleep at just two hours a day. This suggestion becomes imperative when researchers found out that elephants sleep only two hours per day - making them the shortest sleeping mammal. "In addition, it appears that elephants only go into REM, or dreaming, sleep every three to four days, which makes elephant sleep unique".

Most of what scientists previously knew about sleeping elephants came from captive animals, says neuroethologist Paul Manger of the University of the Witwatersrand, Johannesburg. Some days neither elephant slept, and neither ever slept in the same place.

The researchers are planning follow-up studies on more elephants, including males. Most of their sleep occurred between 1.00 and 6.00 am, and the elephants snoozed in different places every night.

If you catch any elephants napping on your next African safari, be careful not to wake them up. However, many studies on elephant sleep have been done in a captive setting or were unable to accurately distinguish rest from sleep.

"This makes an all-encompassing relationship between REM sleep and memory consolidation rather hard to support", Manger says.

There's an old saying that elephants never forget. (2017) Inactivity/sleep in two wild free-roaming African elephant matriarchs - Does large body size make elephants the shortest mammalian sleepers? The domestic horse, at almost 3 hours, is its closest rival. In mammals, REM sleep occurs only when muscles are relaxed and, Manger notes, "When muscle tone is lost, it is very hard to stand while asleep".

A team of researchers in South Africa outfitted two free-roaming female elephants with what are essentially very large Fitbits - an "actiwatch" implanted in the trunk to track sleep and a gyroscope-equipped collar to track what position the elephants were in - and monitored them for 35 days. Trunks, like human hands, are important for exploring and manipulating the world, so they're rarely still for long. The trunk is the most mobile appendage, Manger said, and if it's still for more than five minutes it's reasonable to assume the animal is asleep. Elephant experts have pointed out that large bull elephants often lean against trees to sleep rather than lie down‚ as it would be hard for them to get back up. "There are a lot of things to do‚" said Manger. Animals in captivity don't face the same dangers.

Elephants (both African and Asian) sleep nightly much like you probably do after a night drinking: Sitting or standing with their trunk resting on the ground and for only three to six hours or so, according to the paper.

On several days during the study period, the elephants went without sleep for up to 46 hours and traveled long distances of around 30 kilometers during these periods, possibly to avoid attacks from lions or poachers.

Still, it's unclear how these findings for two females will translate to entire elephant populations.

  • Joanne Flowers