Wild Elephants Might Only Need Two Hours Of Sleep A Night

In a first-of-its-kind study, researchers monitored two African elephants in the wilds of Chobe National Park in Botswana for 35 days to determine how much sleep they got each night. Still, learning more about sleep in elephants, such as why and how they snooze, can help shape wildlife conservation and give scientists clues about human sleep.

In a study by Paul Manger from the University of the Witwatersrand and colleagues, two female wild African elephants in Botswana were outfitted with a Global Positioning System collar complete with a gyroscope to better understand the mysterious slumbering habits of these massive creatures.

Manger says that they attached the Fitbits to two matriarch elephants” trunks, thinking that this body part would be the most accurate to measure the elephants’ activity and “awakeness’.

In addition, they slept lying down only every few nights.

During the research time, the two African elephants didn’t sleep for 46 hours and covered a distance of 30kms at a stretch.

Data collected from the actiwatches indicated that the elephants slept for about two hours each day, mostly in the early morning.

Previous studies of animals in zoos have found they sleep between four and six hours a night, and may sleep while standing or lying down.

“The elephant has well-documented long-term memories”, explained Manger, “but does not need REM sleep every day to form these memories”. In captivity, elephants usually doze off between three and seven hours a day, but they can afford these extra hours of sleep, so to say.

A sample size of two is small, but if the two matriarchs are representative of their species, African elephants may be the shortest-sleeping mammals on Earth, the researchers said.

That “potentially limit [s] their ability to enter REM sleep on a daily basis”, per the researchers. This big mammal has the longest memory and the shortest period of the sleep. The considerably larger grey whale sleeps for 9 hours a day and the giraffe for nearly 5 hours.

They often slept in a standing position, and only lay down to sleep every three to four days. We know that it represents one of the biological imperatives because we need to sleep to survive. The team speculates that these were the only occasions the elephants went into REM sleep, meaning they dreamt infrequently.

The scientists also found they could predict when the elephants slept based on environmental factors like temperature, humidity and wind speed-but not by light.

The main finding was that these elephants slept far less than in other studies of wild or captive elephants. “The hypotheses about restorative functions start to go out the window”, lead author Paul Manger told The Atlantic.

The study was published online yesterday (March 1) in the journal PLOS ONE.

But other researchers believe the size of an elephant’s family group could also influence its sleep duration. “Elephants move with their herd and move very frequently, so animals sleeping a lot would be left behind”.