A new study concluded that elephants have less sleep than any other mammal, including humans. The study says that wild elephants tend to sleep only 2 or 3 hours at night. Scientists believe there is a link between size and sleeping hours.

This is the first study of the kind made about wild elephants. It was published in the Journal Plus One last Wednesday. The study also states that elephants might even support a few all-nighters in a row and that they don’t really have much chance of dreaming.

Wild elephants sleep only two hours a day. Image Credit: New Power

“Elephants really don’t sleep all that much, and this appears to be related to their large size,” said study lead researcher Paul Manger, a professor in the School of Anatomical Sciences at the University of the Witwatersrand in South Africa. “This confirms a long-held suspicion in the field of comparative sleep studies.”

The bigger the animal, the less it sleeps

Previous research has observed the sleep pattern of elephants in captivity. These animals tend to sleep 4 to 6 hours a day, which is not much sleep.

However, it seems that elephants sleep even less when they are in their natural environment. According to Paul Manger, to understand the natural behavior of an animal, it must be studied in its natural environment.

“Sleep needs to be studied in an animal’s natural environment if we are truly to understand it,” said Paul Manger, lead author of the study.

To carry out the research, Manger alongside other researchers focused on two female leaders known as matriarchs; they are the ones who lead the herd. The elephants were African elephants (Loxodonta africana) from Botswana’s Chobe National Park.

They put a GPS collar on them to track their exact location, and they surgically implanted a movement tracker into each elephant’s truck.

They thought that following the movements and activity of the elephants’ trunk was vital to know if the animal was asleep. They said that if no action was perceived for 5 or more minutes, that would possibly mean that the animals were asleep.

By the end of the month-long study, scientists stated that wild elephants sleep on average two hours a day, which is one hour less than the average of the domestic horse, which was considered the mammal that had less sleep until now.

The study led researchers to think there is a link between the size of the animal and the hours of sleep. They say that the bigger the animal, the fewer hours it tend to sleep, maybe because big animals have to spend a great part of their time eating.

However, this relationship is still debated. When comparing elephants in captivity with those in the wild environment, scientists say that it is not surprising those in zoos sleep more because they have nothing to do, they don’t have to search for food nor protect themselves from aggressive animals like lions.

Elephants don’t experience REM sleep

When studying these wild female elephants, researchers noticed that the 2 hours sleep generally occur in the hours before dawn, and they take them in four to five short nap sessions.

Also, elephants tend to walk through the night, up to 19 miles, even resisting several all-nighters without taking extra resting time the days after.  When they sleep, they do it in different places each time, and they do it standing up most of the times. According to scientists, elephants only lay down one hour once or twice a week.

This has led scientists to consider that elephants don’t enter REM sleep like most of the mammals do, including naturally the human beings, because when a mammal dreams they relax their muscles, therefore they could not remain stand still if they enter in REM.

What is most worrisome about the fact elephants don’t enter REM sleep, is that if they don’t dream it is unsure how they consolidate memories. According to Manger, some birds dream in sub-minute bursts.

As well, whales and dolphins live entirely without REM sleep. The purpose of sleeping is not entirely understood yet; however, it is an essential element for living beings to survive.

“REM sleep (or dreaming) is thought to be important for consolidating memories, but our findings are not consistent with this 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,” said Manger.

According to the researchers, this study was useful to set new inquiries about elephants’ patterns of sleep. However, they highlighted that maybe the movement tracker could lead to overestimating the sleep time since the animal could be motionless without falling asleep.

They had considered surgery to record brain function, what would’ve been more accurate, but they believed that a surgery of the kind would border the limits of ethical acceptability.

Source: The Christian Science Monitor