Keven Law via Wikimedia Commons // CC BY-SA 2.0
Keven Law via Wikimedia Commons // CC BY-SA 2.0

We Now Know Why Bearcats Smell Like Buttered Popcorn

Keven Law via Wikimedia Commons // CC BY-SA 2.0
Keven Law via Wikimedia Commons // CC BY-SA 2.0

Nature has produced some delightfully clever mimics, from orchids that dress like fuzzy bees to slow lorises that pretend to be cobras. These knockoffs are sophisticated, but they make sense; the orchids' ruse gets them pollinated, and a cobra costume will help a slow loris live another day. Then there's the binturong, which marks its territory with a scent that bears an uncanny resemblance to the aroma of buttered popcorn. This fact has historically delighted trivia buffs, but left researchers scratching their heads. Now, scientists say they've at least found out how—if not why—the backsides of these animals smell like movie theaters. Their research was published in the journal The Science of Nature.

The binturong (Arctictis binturong), also known as the bearcat, is a clever member of the viverrid family. These sturdy critters make their homes in the forests of South and Southeast Asia, where they can reach more than 3 feet long. When marking their territory, binturongs spray urine on the terrain, as well as on their feet and tails. Then, they use their pee-soggy tails like brushes, painting popcorn-scented markings on every tree they come across.

Scientists had previously attempted—and failed—to identify the chemical components producing the bearcats' buttery calling card. Evolutionary anthropologist Christine Drea and her colleagues decided to try again. They collected urine samples from 33 captive bearcats (13 females and 20 males) at a North Carolina wildlife sanctuary. They then examined the urine samples using a technique called gas chromatography, which can identify and measure the individual chemicals in any given sample.

The bearcats' pee contained 29 different chemicals, but each animal's urine sample was unique. Only one compound appeared in all the samples: 2-acetyl-1-pyrroline, or 2-AP—which just so happens to be the chemical responsible for the smell of buttered popcorn. That is, binturong pee doesn't just smell like buttered popcorn; it smells exactly like buttered popcorn.

But finding 2-AP just raised more questions. In addition to popcorn, the compound is also a part of the aromas of cooked rice and toasted bread. Notice anything funny about those three smells? They all involve cooking. 

"If you were to make this compound, you would have to use temperatures above what most animals can achieve physiologically," Drea said. "How does this animal make a cooking smell, but without cooking?"

The researchers became concerned that the 2-AP was not a binturong chemical at all, but the product of the cooked and processed Iams Chunks kibble the captive bearcats were fed. But sampling the chow revealed no trace of 2-AP.

The scientists' best guess is that the bearcats aren't actually producing cooked chemicals at all—their bacteria are. Previous studies have shown that a common bacterium called Bacillus cereus can use fermentation to make 2-AP.

ZUMA Press, Inc., Alamy
5 Fascinating Facts About Koko the Gorilla
ZUMA Press, Inc., Alamy
ZUMA Press, Inc., Alamy

After 46 years of learning, making new friends, and challenging ideas about language, Koko the gorilla died in her sleep at her home at the Gorilla Foundation in Woodside, California on June 21, 2018. Koko first gained recognition in the late 1970s for her ability to use sign language, but it was her friendly personality that made her a beloved icon. Here are five facts you should know about the history-making ape.


Francine "Penny" Patterson, then a graduate student at Stanford University, was looking for an animal subject for her inter-species animal communication experiment in the early 1970s when she found a baby gorilla at the San Francisco Zoo. Originally named Hanabiko (Japanese for "fireworks child," a reference to her Fourth of July birthdate), Koko took to signing quickly. Some of the first words Koko learned in "Gorilla Sign Language," Patterson's modified version of American Sign Language, were "food," "drink," and "more." She followed a similar trajectory as a human toddler, learning the bulk of her words between ages 2.5 and 4.5. Eventually Koko would come to know over 1000 signs and understand about 2000 words spoken to her in English. Though she never got a grasp on grammar or syntax, she was able to express complex ideas, like sadness when watching a sad movie and her desire to have a baby.


Not only did Koko use language to communicate—she also used it in a way that was once only thought possible in humans. Her caretakers have reported her signing about objects that weren't in the room, recalling memories, and even commenting on language itself. Her vocabulary was on par with that of a 3-year-old child.


Koko was the most famous great ape who knew sign language, but she wasn't alone. Michael, a male gorilla who lived with Koko at the Gorilla Foundation from 1976 until his death in 2000, learned over 500 signs with help from Koko and Patterson. He was even able to express the memory of his mother being killed by poachers when he was a baby. Other non-human primates have also shown they're capable of learning sign language, like Washoe the chimpanzee and Chantek the orangutan.


Koko received many visitors during her lifetime, including some celebrities. When Robin Williams came to her home in Woodside, California in 2001, the two bonded right away, with Williams tickling the gorilla and Koko trying on his glasses. But perhaps her most famous celebrity encounter came when Mr. Rogers paid her a visit in 1999. She immediately recognized him as the star of one of her favorite shows, Mister Rogers' Neighborhood, and greeted him by helping him take off his shoes like he did at the start of every episode.


Koko was never able to have offspring of her own, but she did adopt several cats. After asking for a kitten, she was allowed to pick one from a litter for her birthday in 1985. She named the gray-and-white cat "All Ball" and handled it gently as if it were her real baby, even trying to nurse it. She had recently received two new kittens for her 44th birthday named Ms. Gray and Ms. Black.

Why Do Dogs Crouch Forward When They’re Playing?

Whether they're tilting their heads or exposing their bellies for rubs, dogs are experts at looking adorable. But these behaviors do more than elicit squeals from delighted humans; in many cases, they serve important evolutionary functions. A prime example is the "play bow": If you've ever seen a dog crouch forward with its elbows on the ground and its rear end in the air, wagging tail and all, then you know what it is. The position is the ultimate sign of playfulness, which is important for a species that often uses playtime as practice for attacking prey.

The play bow first evolved in canids as a form of communication. When a dog sees another dog it wants to play with, it extends its front paws forward and lifts up its behind as a visual invitation to engage in a friendly play session. Dogs will "bow" in the middle of playtime to show that they're having fun and wish to continue, or when a session has paused to signal they want to pick it back up. Play bows can also be a sort of apology: When the roughhousing gets too rough, a bow says, “I’m sorry I hurt you. Can we keep playing?”

Play between canines often mimics aggression, and starting off in a submissive position is a way for all participating parties to make sure they’re on the same page. It’s easy to see why such a cue would be useful; the more puzzling matter for researchers is why the ancestors of modern dogs evolved to play in the first place. One theory is that play is crucial to the social, cognitive, and physical development of puppies [PDF]. It’s an opportunity for them to interact with their own kind and learn important behaviors, like how to moderate the strength of their bites. Play also requires the animals to react quickly to new circumstances and assess complex actions from other dogs.

Shiba inus playing outside.
Taro the Shiba Inu, Flickr // CC BY 2.0

Another evolutionary explanation is that playtime prepares puppies for the hunting they do later as adults. Watch two puppies play and you’ll see them stalking, biting, and pouncing on one another—all behaviors canines exhibit in the wild when taking down prey.

Of course, it’s also possible that dogs simply play because it’s fun. This is a strong case for why pet dogs continue to play into adulthood. “Devoting a lot of time to play may be less advantageous for a wild species who spends much of its time hunting or foraging for food, searching for mates, or avoiding predators,” Dr. Emma Grigg, an animal behaviorist and co-author of The Science Behind a Happy Dog, tells Mental Floss. “Many domestic dogs are provisioned by humans, and so have more time and energy to devote to play as adults.”

Because play is a lifelong activity for domestic dogs, owners of dogs of all ages have likely seen the play bow in person. Wild canids, like wolves, foxes, and coyotes, tend to reserve this behavior for members of their own species, but pet dogs often break out the bow for their humans—or anyone else who looks like they might be up for a play session. Grigg says, “One of my dogs regularly play bows to her favorite of our cats.”


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