Chimps Eat Clay In Order to "Detox"

Joining the long list of behaviors we share with chimps, a new study published in PLOS ONE last week details how chimpanzees in the Budongo Forest of Uganda have been observed eating clay in order to access its detoxifying minerals.

"A chimpanzee's diet is mostly leaves, fruits and the occasional monkey. They sometimes eat other things—bark, rotting wood and even soil," Cat Hobaiter, a researcher at University of St. Andrews in the U.K. and co-author of the study, told NPR's The Salt. Typically, chimps rely on decaying swamp trees for a range of minerals they don't get elsewhere. As deforestation limits the availability of edible wood, chimps have upped their intake of clay and clay-rich water in order to supplement their diets.

After first noticing this behavior years ago, researchers began more closely observing the chimpanzees in 1990. They noted instances of both eating clay directly from the ground and drinking clay-rich water via "leaf sponges," or chewed-up leaves that are dipped into water holes to collect liquid.

Clay, which has always been a part of the chimp diet to some degree, has an additional benefit in larger doses: It works to detoxify tannins. The mature leaves that make up most of what chimps eat are full of the bitter polyphenols found in tea, chocolate, and wine, which can have harmful effects when consumed in large quantities.

The mineral-binding structure of the kaolin clay consumed by chimps neutralizes this acidity. Vernon Reynolds, a professor emeritus of biological anthropology at Oxford University and the lead author of the study, said that there's no indication the chimps were suffering from digestive problems: "They're all perfectly healthy, and so [clay-eating] was preventative rather than curing."

These findings are particularly interesting in light of recent research into the disorder known as pica, in which people compulsively crave things that aren't food, such as starch, charcoal, ice—and dirt, or more specifically, kaolin clay.

Cornell nutritional anthropologist Sera Young, author of Craving Earth, theorizes that clay's ability to act as a "mud mask for the gut" might be behind this baffling compulsion. There's evidence that our ancestors were eating dirt at least 2 million years ago, indicating that there is something innately appealing about clay consumption. And Young has found that pregnant women—whose immune systems are slightly surpressed—and people living in hot, humid areas, where pathogens multiply and spread rapidly, are the most susceptible to pica.

"I can assure you that no one has said, 'Actually, Dr. Young, I'm picking up this box of Argo corn starch to protect myself from the pathogens in my environment.' They're saying what the impetus is, the smell and the taste," Young told NPR last year. In healthy humans, the desire to eat clay is more harmful than the tannin-neutralizing properties are worth—the binding properties of the clay don't just flush out the toxins, they absorb the useful nutrients as well.

But the new evidence of chimps consuming kaolin clay supports the theory that pica isn't purely random—it could have evolved as an early protective measure.

Big Questions
Why Do Cats 'Blep'?

As pet owners are well aware, cats are inscrutable creatures. They hiss at bare walls. They invite petting and then answer with scratching ingratitude. Their eyes are wandering globes of murky motivations.

Sometimes, you may catch your cat staring off into the abyss with his or her tongue lolling out of their mouth. This cartoonish expression, which is atypical of a cat’s normally regal air, has been identified as a “blep” by internet cat photo connoisseurs. An example:

Cunning as they are, cats probably don’t have the self-awareness to realize how charming this is. So why do cats really blep?

In a piece for Inverse, cat consultant Amy Shojai expressed the belief that a blep could be associated with the Flehmen response, which describes the act of a cat “smelling” their environment with their tongue. As a cat pants with his or her mouth open, pheromones are collected and passed along to the vomeronasal organ on the roof of their mouth. This typically happens when cats want to learn more about other cats or intriguing scents, like your dirty socks.

While the Flehmen response might precede a blep, it is not precisely a blep. That involves the cat’s mouth being closed while the tongue hangs out listlessly.

Ingrid Johnson, a certified cat behavior consultant through the International Association of Animal Behavior Consultants and the owner of Fundamentally Feline, tells Mental Floss that cat bleps may have several other plausible explanations. “It’s likely they don’t feel it or even realize they’re doing it,” she says. “One reason for that might be that they’re on medication that causes relaxation. Something for anxiety or stress or a muscle relaxer would do it.”

A photo of a cat sticking its tongue out

If the cat isn’t sedated and unfurling their tongue because they’re high, then it’s possible that an anatomic cause is behind a blep: Johnson says she’s seen several cats display their tongues after having teeth extracted for health reasons. “Canine teeth help keep the tongue in place, so this would be a more common behavior for cats missing teeth, particularly on the bottom.”

A blep might even be breed-specific. Persians, which have been bred to have flat faces, might dangle their tongues because they lack the real estate to store it. “I see it a lot with Persians because there’s just no room to tuck it back in,” Johnson says. A cat may also simply have a Gene Simmons-sized tongue that gets caught on their incisors during a grooming session, leading to repeated bleps.

Whatever the origin, bleps are generally no cause for concern unless they’re doing it on a regular basis. That could be sign of an oral problem with their gums or teeth, prompting an evaluation by a veterinarian. Otherwise, a blep can either be admired—or retracted with a gentle prod of the tongue (provided your cat puts up with that kind of nonsense). “They might put up with touching their tongue, or they may bite or swipe at you,” Johnson says. “It depends on the temperament of the cat.” Considering the possible wrath involved, it may be best to let them blep in peace.

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

Why Crows Hold Noisy Funerals for Their Fallen Friends

The next time you hear a murder of crows cackling for no apparent reason, show a little respect: You may have stumbled onto a crow funeral. Crows are among the few animals that exhibit a social response to a dead member of their species. Though their caws may sound like heartbroken cries, such funerals aren't so much about mourning their fallen friends as they are about learning from their mistakes.

In the video below from the PBS series Deep Look, Kaeli Swift, a researcher at the University of Washington's Avian Conservation Lab, investigates this unusual phenomenon firsthand. She familiarized herself with a group of crows in a Seattle park by feeding them peanuts in the same spot for a few days. After the crows got used to her visits, she returned to the site holding a dead, taxidermied crow and wearing a mask and wig to hide her identity. The crows immediately started their ritual by gathering in the trees and crying in her direction. According to Swift, this behavior is a way for crows to observe whatever might have killed the dead bird and learn to avoid the same fate. Flocking into a large, noisy group provides them protection from the threat if it's still around.

She tested her theory by returning to the same spot the next week without her mask or the stuffed crow. She offered the crows peanuts just as she had done before, only this time the birds were skittish and hesitant to take them from her. The idea that crows remember and learn from their funerals was further supported when she returned wearing the mask and wig. Though she didn't have the dead bird with her this time, the crows were still able to recognize her and squawked at her presence. Even birds that weren't at the funeral learned from the other birds' reactions and joined in the ruckus.

Swift was lucky this group of crows wasn't particularly vengeful. Crows have been known to nurse and spread grudges, sometimes dive-bombing people that have harmed one of their own.

[h/t Deep Look]


More from mental floss studios