Chew and Roll: How Cats Make the Most of Catnip

Cats are often a mystery, even to those who are familiar with them. Why do they sleep so much? Why don’t they want your full attention for one minute and the next one? How can they find a way home after being stuck miles away? Haruki Murakami, a writer known for putting cats in novels and essays, once confessed that he didn’t know why. The cat “slides naturally,” he said.

Another mystery: Why do cats love catnip? When exposed to mint-related plants, the majority of domestic cats lick, rub, chew and roll in it. They are full of euphoria and make things high. They also become wild on silver vines, which are not closely related to other plants, especially catnip, but elicit the same response from felines, including large cats such as jaguars and tigers.

For years, this behavior has been another mystery associated with cats. However, a new study published in the journal iScience on Tuesday suggests that the response to catnip and silver vine may be explained by the insect repellent effect of iridoid, a plant chemical that induces high levels. ..

Researchers led by Masao Miyazaki, an animal behavior scientist at Iwate University in Japan, found that when plants were damaged by cats, the amount of these iridoids released from the plants increased by more than 2,000 percent. did. Therefore, perhaps Kitty’s height brings evolutionary benefits: repelling blood-sucking insects.

Christine Vitale, a cat behavior expert at Unity College who was not involved in the study, said the study was based on a strong previous study. Last year, the same lab published a study that found that cats do their best to cover themselves with iridoids like DEET by rolling chemicals and standing up and biting their cheeks. “This shows that cats may benefit from physically placing the compound on their bodies,” Dr. Vitale said.

Carlo Siracusa, an ethologist at the University of Pennsylvania who was not involved in the study, agreed. “Evidence shows that they want their bodies to be scented,” he said. But he added: “Note that quite a few cats do not show this behavior. So why were they chosen this way?”

As an evolutionary adaptation, insect repellent iridoids probably do more to protect plants from herbivorous insects than to help cats avoid insect bites. Plants often release irritants when damaged, which helps drive off attackers and releases other chemicals that convey danger to their neighbors. “Plants are masters of chemical warfare,” said Marco Galio, a neurobiologist at Northwestern University who is not involved in new research.

Last year, Dr. Galio and his colleagues published a report linking nepetalactone, the main insect repellent for catnip, to a receptor protein that causes irritation to mosquitoes and related insects. Receptors that are also present in humans and cats can be triggered by tear gas. However, Dr. Galio found that nepetalactone did not adversely affect humans and, although it sent cats to ecstasy spasms, activated this particular receptor (called TRPA1) in many insects.

In their latest study, Dr. Miyazaki and his colleagues measured the chemical composition of the air just above the leaves of catnip and silver vine. Next, they measured the iridoid levels of the leaves themselves. They released catnip leaves that cats broke at least 20 times more nepetalactone than intact leaves, and damaged silvervine leaves released at least 8 times more similar iridoids than intact leaves. I found it to release. The interaction between cats and silver vines also changed the composition of the plant insect repellent cocktail and made it even more powerful.

After rubbing the face or body against the plant, the cat is always covered with a tough layer of pest begone.

This finding, coupled with previous work by Dr. Miyazaki and his team, supports the early claim that at least some of the benefits of the Kitty Catnip boom are to stop mosquitoes and flies. Such an action called “self-anointing” is not the first in the animal kingdom. Mexican spider monkeys are known to fill themselves with different types of leaves, perhaps for social or sexual purposes, and hedgehogs often rub toxins on their spines.

Still, there are still many questions to be answered, such as why only cats respond euphorically to catnip and silver vine, and why only some of these cats do so. Dr. Galio was enthusiastic about new research, but offered a cautious approach. “What do I know?” He said. “I wasn’t there to see evolution happen.”

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