Scientists are scratching their heads after making a discovery about elephants that doesn’t seem to fit with reality. Despite the fact that sleep is associated with memory retention, and also despite the fact that elephants are known for their memory, this huge animal sleeps only for a couple hours a day in the wild. The study, published in PLOS One, makes the claim based on two wild African elephants in Botswana that were fitted with a device to track their movements and sleeping habits over a period  of 35 days.

Elephants also apparently also stay awake for up to 48 hours if they are threatened by predators or poachers. That’s a lot different from the behavior of elephants in captivity, which will sleep for six hours per day, somewhat comparable to the sleeping habits of humans.

Another interesting finding is that elephants dream every three or four days when they enter Rapid Eye Movement (REM) sleep. Entering REM sleep so infrequently puzzles scientists, as REM is associated with memory.

“Studies of sleep in captive elephants have shown that they sleep for four to six hours per day; however, the current study shows that in their natural habitat, wild, free-ranging elephants sleep only for two hours per day, the least amount of sleep of any mammal studied to date, but this appears to be related to their large body size,” Paul Manger from University of the Witwatersrand, South Africa, said in the statement. “In addition, it appears that elephants only go into REM, or dreaming, sleep every three to four days, which makes elephant sleep unique.”