Elephants can Function on only Two Hours of Sleep per Day

Fagjun | Published 2017-03-03 00:00

Elephants can get more things done in a day than any other mammal on earth.

At just two hours of shut-eye, elephants need the least sleep of all mammals. This may come in handy for the rest of us who have jobs to go to, deadlines to meet, and predators to run away from. Alas, we don't all have the fortune of having evolved in the same way. Research shows that there may be unique reasons as to why these giant pachyderms need so little sleep.

Paul Manger from the University of Witwatersrand studied wild elephants in northern Botswana for the research. He and his colleagues kept an eye on two females over the course of 35 days. To monitor sleep patterns, the researchers attached motion sensors to the trunks of his subjects.

Usually, taking electrical recordings of a subject's brain is the best way to measure and monitor sleep. However, elephant skulls are too thick for electrodes to penetrate through. Because trunks are the most active part of an elephant's body, the team decided that it was the next best choice. The researchers thus assumed that an idle trunk indicates sleep. “We figured when it hadn’t been used for 5 minutes, the elephant was probably asleep,” Manger explains.

Active trunk = wide awake elephant

Interesting Observations

The findings revealed a number of interesting things about the sleeping giants. Not only do elephants need only two hours of sleep, they don't even need all two hours in one go. Instead, they fall into what is known as polyphasic sleep from the hours of 1am to 6am. In polyphasic sleep, the subjects get the slumber they need in an average of four to five increments.

Another interesting discovery is that when elephants lose sleep, they don't need to make up for it later on. The ones in the study would even sometimes go 48 hours without sleep. According to observations, they never needed to sleep more on the following days. The researchers also noticed that during those sleepless 48 hours, the elephants traveled long distances, possibly to avoid predators.

Do Elephants Dream?

And if they do, what do they dream about?

Perhaps the most interesting discovery is that elephants don't always sleep lying down. The ones in the study slept lying down only on 10 out of the 35 days. This may indicate that elephants don't usually fall into REM sleep. During REM sleep, the muscles in the body relax, making standing up impossible. Dreams also occur during REM sleep, which means that elephants may not always dream. It may also mean that they enter the REM stage only in five- to 10-second bursts.

So why do elephants need so little sleep? Larger animals generally tend to sleep less because they have to eat more. “Elephants can eat up to 300 kilograms of food a day,” Manger says. Traveling long distances to escape from predators, be they beast or man, could also be a factor.

While informative, these new discoveries have also raised more questions about how elephants live and sleep. The researchers plan to study more elephants in the future to answer these questions, especially those about the occurrence of REM sleep.

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