Wild African elephants may not care about their step counts, but scientists who fitted two elephants with “fitbits” believe the results could change our understanding of sleep.
Most mammals sleep. But the purpose of this period of inactivity and vulnerability still baffles scientists. Big animals – like elephants – are known to sleep less than smaller animals. But until now their sleeping patterns have only been studied in captivity.
In the wild elephants sleep less says Paul Manger, a neuroscientist at the University of Witwatersrand in South Africa. He and his team implanted fitbit-like gyroscopic devices in the trunks of two elephant cows roaming the Chobe National Park in Botswana. They clocked the pair sleeping on average two hours per day, the shortest measured in any land mammal.
The elephants often also skipped a night’s sleep when traveling, perhaps to avoid poachers or predators, and only slept lying down every three to four nights. This might limit their capacity for rapid eye movement or REM sleep, which in humans is associated with dreaming.
One theory states that we dream to consolidate our memories. But elephants are renowned for their capacity to remember things. This questions the link between REM sleep and higher brain function, says Manger. “We are probably going to have to re-evaluate what REM sleep is for.” He says this is backed by studies on dolphins and whales, also intelligent mammals, which seem not experience REM sleep at all.
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. This is interesting, says Manger, since it corresponds to findings that Bushmen in Southern Africa who live in out the open wake up not at dawn like their housebound counterparts, but at the coldest time of night.
These results could change how we think about sleeping disorders and how to treat them, says Manger. Light therapy is used to treat people with wonky sleeping patterns, but this might not be the right approach.
“Light is not a big thing guiding when you go to sleep or when you wake up. It’s what the Weather Channel calls the ‘real feel’ of the weather and the environment that’s doing that for us,” he says.
Manger admits his study was limited, as only two elephants were tracked. Given more funding he would like to fit a male next, but it’s a challenge since they roam far into neighboring countries. They would also like to track more than one female in a herd to see if they take turns keeping guard.
He says such studies could ultimately help scientists understand the evolution of sleep and its purpose. “Knowing how different animals sleep and why they do so in their own particular way, helps us to understand how humans sleep, why we do, and how we might get a better night’s sleep.”
The study is powerful despite its limitations, says Tom de Boer, a sleep expert at Leiden University in The Netherlands who was not involved in the research. “We know a lot about sleep, but know a lot less how animals, including humans, sleep in the wild.” The technology may be of limited use in smaller animals, he says. “In general, however, I am positive about this study and I think more should be done in this direction.