Professor Paul Manger and his colleagues at the University of the Witwatersrand in South Africa followed two elephant matriarchs from a herd in Chobe National Park for 35 days to determine their sleep cycles, which remained little known at this time.
To establish sleep habits, researchers implanted trackers under the skin of their horns (which is the most mobile part of these waking animals) to send signals when the animals remained motionless for more than five minutes. The two animals were also equipped with a collar equipped with a gyroscope to detect positions during their sleep, standing or lying down.
In zoos, elephants usually sleep four to six hours. The study published in the journal Plos One shows that in their natural environment, the largest terrestrial mammals only sleep two hours, usually at night.
During the observation period, these two elephants even remained without sleep for up to 46 hours in a row, traveling distances of about 30 kilometers. The reason? This could allow them to move away from poachers or lions and other predators.
In addition, they slept lying on the ground only every three to four days for an hour. The rest of the time, they remained standing to sleep.
This reality may limit their ability to regularly have so-called paradoxical (REM) sleep phases, during which dreams occur, making them unique in this regard, researchers say.
Did you know? All animals sleep, some much, some less. For example, dolphins, who must rise to the surface to breathe, remain active when they sleep: half of their brain sleeps while the other half remains awake. Generally, small mammals sleep longer than larger mammals. For example, lazy sleep about 14 hours a day and humans around 8 hours.
Sleep, this mystery
The REM part (rapid eye movements), which in humans accounts for 25% of the total sleep time, is only a small part of their time spent sleeping, suggesting that elephants may not dream That every three to four days.
Dreaming is considered important to consolidate memory, which does not seem to be true for elephants, whose long memory is well known.
Professor Paul Manger
In addition, the data collected show that some environmental factors other than daylight, such as temperature and humidity, affect the timing of elephants falling asleep and waking.
A parallel with humans
Understanding how to sleep different animals is important to get to know them better. “It also makes it possible to discover new information that could help to develop better strategies to protect them,” says Professor Manger.
Sleep deprivation can even, over a relatively short period of time, lead to brain damage and, in the longer term, death, as can be seen with certain rare diseases such as familial fatal insomnia (IFF), a genetic neurodegenerative disease Attacks the central nervous system.