A new study found African elephants in the wild only sleep two hours a day.

African Elephants Sleep
Credit: Thomas Dressler/Getty Images/Gallo Images

If you catch any elephants napping on your next African safari, be careful not to wake them up.

Humans tend to get cranky if they regularly get less than five hours of sleep, but that's much more than a full day's rest for African elephants living in the wild.

While rescue elephants in India have shown an affinity for cozy knit sweaters, African elephants in the wild sleep as little as two hours a day, and only lay down to sleep (for an hour or so) every few days, according to a new study published in the journal PLOS ONE.

Researchers studied elephants at Chobe National Park in Botswana with a scientific version of a Fitbit.

African Elephants Sleep
Credit: Peter Malsbury/Getty Images

“Understanding how different animals sleep is important for two reasons,” Professor Paul Manger, from the School of Anatomical Sciences at Wits University, said in a statement. “First, it helps us to understand the animals themselves and discover new information that may aid the development of better management and conservation strategies, and, second, 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.”

To judge whether or not the elephants were sleeping, the researchers measured trunk activity.

“We reasoned that measuring the activity of the trunk, the most mobile and active appendage of the elephant, would be crucial, making the reasonable assumption that if the trunk is still for five minutes or more, the elephant is likely to be asleep,” said Manger.

African Elephants Sleep
Credit: Getty Images/Hemis.fr RM

The study also found that when the elephants slept had more to do with temperature and what was going on around them than with sunset and sunrise, and that they likely only dream every few days. When faced with a potential predator, the elephants will skip a night's sleep completely and just keep on walking away from the danger zone (they must know those lazy lions will get tired eventually).

Though some spend much more time lying around than others—carnivores tend to sleep more than herbivores, who need to spend more time grazing, according to the Center for Sleep Research at UCLA—all animals do sleep. However, "the ultimate purpose of sleep is yet to be discovered,” said Manger.