You probably need anywhere from seven to ten hours of sleep a night. But if you're someone who especially enjoys a full night of shuteye, just be thankful you aren't an elephant.
Scientists know a lot about the sleep patterns of captive elephants, but generally those elephants live the good life, and probably sleep more than usual. A team of researchers from South Africa, Botswana, and the United States couldn't find good data on wild elephants subject to the risk of predators, so they decided to follow a pair of matriarchs' sleep patterns for a month.
"The results of this study reveal a far richer story of elephant rest and sleep than would be predicted from captive studies," the authors write in the study published today in PLoS One.
Elephants (both African and Asian) sleep nightly much like you probably do after a night drinking: Sitting or standing with their trunk resting on the ground and for only three to six hours or so, according to the paper. But the researchers thought that, based on their harsher lives, wild elephants would only sleep around two and a half hours. If you were drunkenly passed out on the subway, you'd probably sleep a little less than if you drunkenly passed out in your bed.
And if you went a long time on two and a half hours of sleep per night, you'd probably have trouble recognising other people's emotions or even become the victim of a tragic accident, according to a National Institute of Health fact sheet.
The researchers implanted activity monitors into their subjects' trunks, put a GPS collars on them and monitored them for 35 days from afar. If the trunks weren't moving for five minutes, the researchers took this as a sign that the elephants were asleep -- the study points out that this could overestimate sleep times.
Elephant sleeping patterns (Image: Gravett, et al)
The healthy 30-year-old Matriarch 1 slept for 2.3 hours on average in bouts distributed mainly at night, while the 37-year-old Matriarch 2 only slept for 1.8 hours, on average. Some days neither elephant slept, and neither ever slept in the same place. Matriarch 1 spent 15.17 per cent of total sleep time in a recumbent position, while Matriarch 2 spent 12.00 per cent of total sleep time in a recumbent position.
There were plenty of other factoids the researchers pulled out from monitoring the restless pachyderms. For example:
Matriarch 1 was a "left-trunker", while Matriarch 2 was a "right-trunker..." Of the time spent in recumbent sleep, Matriarch 1 spent 48.4% lying in her left side, and 51.6% lying on her right side, while Matriarch 2 spent 71.3% lying on her left side and 28.7% lying on her right side, indicating no relationship between trunk side preference and recumbent sleep side preference.
The main finding was that these elephants slept far less than in other studies of wild or captive elephants. If the results hold, then elephants would sleep the least of any mammal, less than horses ,which sleep around three hours per day, or giraffes, sleep three to four, according to the study's reporting. The researchers guess that the elephant's sleepless lifestyle is due in part to its large body combined with a slew of other factors, like the risk of being attacked, environmental conditions, as well as needing to eat a lot of food.
The study only tracks two wild elephants, and I've asked the researchers how they plan on increasing the statistics, or if the collar could wake the elephants up. You probably won't want to judge how all humans sleep based on how two people sleep for a month, for example.
But if you're looking to get a better night's sleep, best not ask an elephant for advice.