Cats, so often, are a mystery, even to those who know them best. Why do they sleep a lot? Why do they need your full attention one minute, none the subsequent? How can they find their way back home after being stranded miles away for years? The author Haruki Murakami, who is thought for putting cats in his novels and essays, once confessed to not knowing why he does so; a cat “sort of naturally slips in,” he said.
Another mystery: Why do cats love catnip? When exposed to the plant, which is said to mint, the majority of domestic cats will lick it, rub against it, chew it and roll around in it. They brim with euphoria, getting high off the stuff. They also go wild for other plants, particularly silver vine, which will not be closely related to catnip but elicits the identical response from felines, including big cats like jaguars and tigers.
For years, this behavior was just one other cat-related enigma. But a latest study, published Tuesday within the journal iScience, suggests that the response to catnip and silver vine may be explained by the bug repellent effect of iridoids, the chemicals within the plants that induce the high.
Researchers, led by Masao Miyazaki, an animal behavior scientist at Iwate University in Japan, found that the quantity of those iridoids released by the plant increased by greater than 2,000 percent when the plant was damaged by cats. So perhaps kitty’s high confers an evolutionary advantage: keeping bloodsucking insects at bay.
Kristyn Vitale, a cat behavior expert at Unity College who was not related to the research, noted that the study built on strong previous work. Last yr, the identical lab published a study that found that cats would try their best to coat themselves in DEET-like iridoids, whether by rolling on the chemicals or by rising as much as nuzzle them with their cheeks. “This indicates there may be a benefit to the cat physically placing the compounds on their body,” Dr. Vitale said.
Carlo Siracusa, an animal behaviorist on the University of Pennsylvania who also was not involved within the research, concurred. “The evidence shows that they want to impregnate their body with the smell,” he said. But, he added, “keep in mind that a sizable chunk of cats don’t show this behavior. So why would they have been selected in this way?”
As an evolutionary adaptation, bug-repellent iridoids probably do more to guard plants from herbivorous insects than to assist cats avoid bug bites. Plants often release irritants when damaged, which helps to ward off attackers, and so they emit other chemicals that communicate danger to their neighbors. “Plants are masters of chemical warfare,” said Marco Gallio, a neurobiologist at Northwestern University who was not affiliated with the brand new study.
Last yr, Dr. Gallio and his colleagues published a report that linked the first bug repellent in catnip, nepetalactone, to a receptor protein that triggers irritation in mosquitoes and related insects. The receptor, which can be present in humans and cats, may be set off by tear gas. But Dr. Gallio found that although nepetalactone had no negative effect on humans and sent felines into spasms of ecstasy, it did activate this particular receptor (called TRPA1) in lots of insects — an added bonus for cats rolling around of their drug of alternative.
In their most up-to-date study, Dr. Miyazaki and his associates measured the chemical composition of the air immediately above leaves — each intact and damaged — of catnip and silver vine. Then they measured the iridoid levels within the leaves themselves. They found that catnip leaves mangled by cats released at the very least 20 times more nepetalactone than intact leaves did, while damaged silver vine leaves released at the very least eight times the quantity of comparable iridoids than did intact leaves. The cats’ interactions with silver vine also modified the composition of the plant’s bug-repelling cocktail, making it even stronger.
After rubbing their faces and bodies against the plants, cats are sure to be coated in a strong layer of Pest Begone.
This finding, paired with Dr. Miyazaki and his team’s previous research, supports nascent claims that at the very least a part of the good thing about the kitty catnip craze is to stave off mosquitoes and flies. Such behavior, called “self-anointing,” wouldn’t be the primary of its kind within the animal kingdom. Mexican spider monkeys have been known to smear themselves with different sorts of leaves, probably to serve a social or sexual purpose, and hedgehogs often rub toxins onto their spines.
Still, there are lots of questions left to be answered, including why seemingly only felines exhibit a euphoric response to catnip and silver vine, and why only a few of these felines achieve this. Dr. Gallio, while passionate about the brand new study, offered a cautious approach. “What do I know?” he said. “I wasn’t there to see evolution happen.”