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Chewed and rolled: how cats get the most out of their catnip high

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Cats are so often a mystery, even to those who know them best. Why do they sleep so much? Why do they want your full attention one minute and none the next? How can they find their way? back House after being stranded for miles for year† The writer Haruki Murakami, who is known for having once incorporated cats into his novels and essays… known person not to know why he does it; a cat “naturally slips in,” he said.

Another mystery: why do cats like catnip? When exposed to the plant, which is related to mint, majority of the house cats will lick it, rub it, chew it, and roll around in it. They are bursting with euphoria and getting high on the stuff. They also get wild on other plants, especially the silver vine, which isn’t closely related to catnip but elicits the same response in cats, including big cats like jaguars and tigers.

For years, this behavior was just another cat-related conundrum. But one new studypublished Tuesday in the journal iScience, suggests that the reaction to catnip and silver vine may be explained by the animal repellent effect of iridoids, the chemicals in the plants that trigger the high.

Researchers, led by Masao Miyazaki, an animal behavior scientist at Iwate University in Japan, found that the amount of these iridoids released by the plant increased by more than 2,000 percent when the plant was damaged by cats. So maybe Kitty’s high offers an evolutionary advantage: keeping bloodsucking insects at bay.

Kristyn Vitale, a cat behavior expert at Unity College who was not involved in the study, noted that the study built on strong previous work. Last year, the same lab published a study showing that: cats would go out of their way to coat themselves with DEET-like iridoidseither by rolling over the chemicals or standing up to sniff them with their cheeks. “This indicates that there may be an advantage for the cat to physically place the compounds on their body,” said Dr. vital.

Carlo Siracusa, an animal behaviorist at the University of Pennsylvania who was also not involved in the study, agreed. “The evidence shows that they want to impregnate their bodies with the scent,” he said. But, he added, “keep in mind that a significant proportion of cats do not exhibit this behavior. So why would they have been selected this way?”

As an evolutionary adaptation, insect repellent iridoids likely do more to protect plants from herbivorous insects than to help cats avoid insect bites. Plants often release irritants when damaged, which help repel attackers, and they emit other chemicals that transmit danger to their neighbors. “Plants are masters of chemical warfare,” said Marco Gallio, a neurobiologist at Northwestern University who was not involved in the new study.

Last year, Dr. Gallio and his colleagues published a report which linked the primary insect repellent in catnip, nepetalactone, to a receptor protein that causes irritation in mosquitoes and related insects. The receptor, which is also present in humans and cats, can be activated by tear gas. But dr. Gallio found that while nepetalactone had no negative effect on humans and sent cats into ecstasy spasms, it activated this particular receptor (called TRPA1) in many insects — an added bonus for cats rolling around in their drug of choice.

In their most recent study, Dr. Miyazaki and his collaborators examined the chemical composition of the air directly above the leaves – both intact and damaged – of catnip and silver vines. Then they measured the iridoid levels in the leaves themselves. They found that catnip leaves mutilated by cats released at least 20 times more nepetalactone than intact leaves, while damaged silver vine leaves released at least eight times as many similar iridoids as intact leaves. The cats’ interactions with silver vine also changed the composition of the plant’s repellent cocktail, making it even more potent.

After rubbing their faces and bodies against the plants, cats are sure to be covered in a solid coat of Pest Begone.

This finding, combined with Dr. Miyazaki and his team support emerging claims that at least part of the benefit of the catnip fad is to stave off mosquitoes and flies. Such behavior, called “self-anointing,” would not be the first of its kind in the animal kingdom. Mexican spider monkeys are known to rub oneself with different types of leaves, probably to serve a social or sexual purpose, and hedgehogs often rub toxins on their spine.

Still, many questions remain to be answered, including why seemingly only cats exhibit a euphoric response to catnip and silver vine, and why only a few of these cats do. dr. Gallio, while enthusiastic about the new study, offered a cautious approach. “What I know?” he said. “I wasn’t there to see evolution happen.”

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