You probably haven’t heard of the binturong before. It’s also known as the bearcat, which confusingly is neither a bear nor a cat, a peculiar type of solitary mammal best known as giving off a rather unique scent – that of particularly hot, buttery popcorn.
The origin of this truly novel odor has long-baffled zookeepers, but a team working with bearcats at the even more confusingly named Carolina Tiger Rescue in Pittsboro, North Carolina, think they’ve cracked it. Their paper, appearing in the journal The Science of Nature, reveals that the smell is effusing from their urine, meaning that it is probably used as a territorial marker.
Perhaps more startlingly, the chemical compound responsible for the smell is actually found in real popcorn. Without eating it themselves, the researchers are still somewhat bemused as to how the compound is being generated.
“If you were to make this compound, you would have to use temperatures above what most animals can achieve physiologically,” Christine Drea, a professor of evolutionary anthropology at Duke University and coordinator of the study, said in a statement. “How does this animal make a cooking smell, but without cooking?”
Previous researchers poked around at the tail-based scent glands of this curious critter, hoping to find the compound in pockets of secretions, but to no avail. However, while checking the urine samples of 33 bearcats at this American nature reserve, taken during routine health checks, this team of intrepid scientists had their eureka moment.
Some zookeepers name their binturongs after various popcorn brands thanks to their memorable stench. TassiloRau/Wikimedia Commons; CC BY-SA 3.0
Using a technique called gas chromatography-mass spectrometry, which looks at the molecular components of various substances, the researchers found that one chemical compound stood out from all the rest: 2-acetyl-1-pyrroline, or 2-AP. Remarkably, this compound gives genuine, edible popcorn its drool-inducing smell, and it seems that it’s also responsible for giving the bearcat’s pee an uncomfortably delectable scent.
Not only was this compound omnipresent in the bearcats’ urine samples, but it was also found to not degrade as quickly as many of the others. This was demonstrated rather publicly when a shipment of frozen bearcat urine was inadvertently left on a strip of hot tarmac, and its smell remained rather pungent for the duration.
They also noted that males secrete more 2-AP than females, which the researchers linked to higher levels of androgens, a group of male sex hormones. All in all, the evidence implies that the urine, which is liberally sprayed on the ground as well as on their own feet, is used as a marker designed to ward off other bearcats competing for resources, and as a calling card for potential mates.
They note that 2-AP normally forms in popcorn when high temperatures initiate chemical reactions between sugars and amino acids in the corn kernels. Bearcats don’t tend to include popcorn in their normal diets, though, so the researchers were somewhat at a loss when it came to explaining where this compound comes from.
The most likely explanation is that bearcat urine often encounters bacteria that use it as a source of nutrients. When they begin to break down the urine, they inadvertently produce 2-AP, very gradually, over time, which explains why the smell of popcorn lingers long after the bearcat has done its business.