Professor Paul Manger from Wits University and his colleagues are using a tracker called an Actiwatch to study elephant sleep patterns in Botswana. They removed the watches' bands, insulated them with electrical tape and biologically inert wax, then attached them to the elephants' trunks. The trunk is the most mobile appendage, Manger said, and if it's still for more than five minutes it's reasonable to assume the animal is asleep.

Using the loggers and GPS collars, researchers found the elephants slept for two hours per day on average. They slept standing up most of the time, only lying down for about an hour every three or four days. This is likely the only time they were able to go into REM sleep, which means elephants possibly don't dream on a daily basis. The team also discovered the pachyderms could go without snoozing for up to 48 hours when disturbed by predators or poachers. Instead, they'd walk up to 18 miles away from the disturbance, giving up a night's sleep to avoid danger.

Previous behavioral research found zoo elephants can sleep for around four hours per day, either standing or lying down. If this new study is confirmed, wild elephants will have the shortest-known sleep time of any land mammal.

"Understanding how different animals sleep is important for two reasons," Manger told Phys.org. "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."