Original image
jude via Flickr Creative Commons // CC BY 2.0

Wild Elephants May Get the Least Sleep of Any Mammal

Original image
jude via Flickr Creative Commons // CC BY 2.0

Sleep is a funny thing. We literally can’t live without it, yet there’s still a lot about it that we just don’t understand. Now, new insight into the unconscious hours of African elephants may muddle the matter further, as a study in the journal PLOS One finds that the massive beasts spend barely any time asleep at all.

Scientists have hypothesized that the size of a mammal’s body is negatively associated with the amount of time it spends sleeping; in other words, big animals sleep less than small ones. Current record holders for shortest sleep time are the domestic horse (two hours, 53 minutes) and pony (three hours, 20 minutes).

While generally accepted, the theory has been tough to test, since you can’t exactly invite a whale into the laboratory for an overnight sleep study. Many studies have focused on captive animals for this reason, but there’s often a big difference between the lives of animals in zoos and those roaming free.

To check in on the sleeping habits of the wild African elephant (Loxodonta africana), researchers focused on the middle-aged matriarchs of two different herds. The scientists fitted each elephant with a collar to monitor her location and body position. (Elephants have two sleeping positions: lying down, which allows for deep REM sleep, and standing up, which is more of a shallow-sleep, nap-type situation.) They also implanted a small movement tracker at the tip of her trunk. Then both elephants were released to go about their lives as usual. The researchers took the trackers back 35 days later and reviewed the data they’d collected.

As it turns out, the elephants had been living remarkably busy lives. Like high-powered businesspeople, they rarely lay down—just once every three or four nights. The rest they did get—mostly while standing—was shallow and brief, averaging about two hours per night. Some nights they just kept walking and never slept at all.

“Studies of sleep in captive elephants have shown that they sleep for four to six hours per day,” study co-author Paul Manger of the University of the Witwatersrand said in a press statement. “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.”

What this means for elephants and other mammals remains to be seen. With just two participants, this was a very small study, and the researchers only tracked movement, not sleep itself. One of the two elephants was also caring for a calf, a responsibility that likely cut into her sleeping time.

Watch a School of Humpback Whales 'Fish' Using Nets Made of Bubbles 

Just like humans, humpback whales catch many fish at once by using nets—but instead of being woven from fibers, their nets are made of bubbles.

Unique to humpbacks, the behavior known as bubble-net feeding was recently captured in a dramatic drone video that was created by GoPro and spotted by Smithsonian. The footage features a school of whales swimming off Maskelyne Island in British Columbia, Canada, in pursuit of food. The whales dive down, and a large circle of bubbles forms on the water's surface. Then, the marine mammals burst into the air, like circus animals jumping through a ring, and appear to swallow their meal.

The video offers a phenomenal aerial view of the feeding whales, but it only captures part of the underwater ritual. It begins with the group's leader, who locates schools of fish and krill and homes in on them. Then, it spirals to the water's surface while expelling air from its blowhole. This action creates the bubble ring, which works like a net to contain the prey.

Another whale emits a loud "trumpeting feeding call," which may stun and frighten the fish into forming tighter schools. Then, the rest of the whales herd the fish upwards and burst forth from the water, their mouths open wide to receive the fruits of their labor.

Watch the intricate—and beautiful—feeding process below:

Original image
Big Questions
Why Do Dogs Love to Dig?
Original image

Dog owners with green thumbs beware: It's likely just a matter of time before Fido turns your azalea bed into a graveyard of forgotten chew toys. When dogs aren't digging up your prized garden, they can be found digging elsewhere in your yard, at the beach, and even between your couch cushions at home. But what exactly is behind your dog's drive to turn every soft surface he or she sees into an excavation site?

According to Dr. Emma Grigg, an animal behaviorist and co-author of The Science Behind a Happy Dog, this behavior is completely normal. "When people say 'why do dogs dig,' the first thing that always comes to mind is 'well, because they're dogs,'" she tells Mental Floss. The instinct first appeared in dogs' wolf ancestors, then it was amplified in certain breeds through artificial selection. That's why dogs that were bred to hunt rodents, like beagles and terriers, are especially compelled to dig in places where such animals might make their homes.

But this tendency isn't limited to just a few specific breeds. No matter their original roles, dogs of all breeds have been known to kick up some dirt on occasion. Beyond predatory urges, Dr. Grigg says there are two main reasons a dog may want to dig. The first is to cool off on a hot day. When stuck on an open lawn with little to no shade, unearthing a fresh layer of dirt untouched by the sun is a quick way to beat the heat.

The second reason is to stash away goodies. Imagine your dog gets bored with chewing his favorite bone but knows he wants to come back for it later. Instead of leaving it out in the open where anyone can snatch it up, he decides to bury it in a secret place where only he'll be able to find it. Whether or not he'll actually go back for it is a different story. "There's a disconnect with modern dogs: They know the burying part but they don't always know to dig it up," Dr. Grigg says.

Because digging is part of a dog's DNA, punishing your pet for doing so isn't super effective. But that doesn't mean you should stand idly by as your yard gets turned inside-out. When faced with this behavior in your own dog, one option is to redirect it. This can mean allowing him to dig in a designated corner of the yard while keeping other parts off-limits, or setting up a raised flowerbed or sandbox especially to satisfy that urge. "You can get him interested in the area by burying a couple bones or some interesting things in there for him to dig," Dr. Grigg says. "I like the idea of buried treasure."

If your dog's motive for digging is more destructive than practical, he may have an energy problem. Dogs require a certain amount of stimulation each day, and when their humans don't provide it for them they find their own ways to occupy themselves. Sometimes it's by chewing up shoes, toppling trash cans, or digging ditches the perfect size for twisting ankles. Fortunately, this is nothing more walks and playtime can't improve.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at


More from mental floss studios