When a cat bites a catnip, it acts as an insect repellent spray | Chemistry

Even the most aloof cats, only a few catnip leaves can cause an agitated bout of chewing, kicking, and rolling.

Silver Vine-or actinidia polygama In Japanese — causes a similar plant-induced euphoria to our cat friends. The response certainly looks fun, but until recently, scientists weren’t sure if cat behavior really had any benefits other than pure joy.

New research, Release This week iScience, When a cat is playing (and damaging) with either catnip or silver vine, the leaves of the plant actually release higher levels of compounds, suggesting that it has the advantage of repelling mosquitoes. doing. Both plants can act as a kind of natural insect repellent spray, and when the cat bites the leaves, the insect repellent spray becomes even more effective. Researchers at Iwate University in Japan, who have been investigating the interaction of cats with catnip and Actinidia polygama for several years, were behind the study...

However, rolling in the leaves is only one component of the cat’s response to these plants. Masao MiyazakiThe ethologist and author of the study at Iwate University explained that cats are engaged in four major behaviors, either catnip or silver vine: licking, chewing, rubbing, and rolling. In a previous study, Miyazaki found that it was very important to transfer iridoids, the chemicals that cause cat endolphin rush, to cat fur and rub or roll to repel mosquitoes. It states. If rubbing or rolling the leaves of silver grapes is the method of insect repellent spraying for cats, this does not yet explain why cats lick or bite the leaves, other than getting taller. ..

In a new study, researchers looked more closely at what happens at the chemical level when leaves are damaged by cats. They first collected intact silver vine leaves, as well as leaves chewed by cats and crumpled by hand. Chemical analysis showed that damage inflicted by both cats and humans increased the release of various iridoids into the leaves. Damaged leaf chemistry cocktails were also less dominated by a single chemical and instead had a more even balance of five different chemicals.

Researchers then tested these various chemical cocktails to see how cats and mosquitoes react to each other. Given a tray of intact and damaged silver vine leaves, the cat spent more time licking and rolling the damaged leaves. And when researchers synthesized the chemical cocktails found on these leaves, the cats spent more time on the damaged leaf cocktails again.

Cats preferred a more balanced iridoid mixture compared to a simpler mixture, even if the levels of nepetalactol, the main iridoid of the silver vine, were the same. Previously thought that nepetalactol attracted cats, this new discovery reveals that the mixture of chemicals has a special appeal. “I was really surprised that the combination of iridoid compounds boosted the response of cats,” he says. Reiko UenoyamaA graduate student at Iwate University and the lead author of both studies.

The complex chemical mixture that is most attractive to cats was also the most repellent to mosquitoes. To compare the insect repellent properties of the mixture, the researchers put the mosquitoes in a transparent box and placed a shallow dish inside. Adding a complex chemical mixture from damaged leaves to the dish allowed the mosquitoes to escape faster than adding a simpler mixture from intact leaves.

Silvervine responded to cat damage by diversifying its chemical profile, but catnip did not. Researchers repeated all the experiments on the catnip and found very different results. The main iridoid chemical in catnip is nepetalactone, not nepetalactol. This is true regardless of leaf damage. When a cat bites a catnip, the leaves significantly increase the emission of nepetalactone alone.

Despite this different reaction to damage, being crumpled makes catnip leaves more attractive to cats and more repellent to mosquitoes. However, in this case, the reaction was due to higher levels of a single chemical. And when comparing the plants to each other, a large amount of catnip cocktail was needed to provoke the same reaction as a very small amount of silver vine cocktail from cats and mosquitoes. Still, the catnip leaves themselves were as attractive to cats as the silver vine leaves because the amount of chemicals released by the catnip leaves was so high overall.

It is not clear to scientists why even small, complex mixtures of chemicals are so effective in triggering reactions. “Unfortunately, I don’t know why cocktails responded so strongly to cats and mosquitoes,” says Miyazaki. But despite these protracted questions Benjamin RichmanA plant biochemist at the University of York, who was not involved in the study, said the study “emphasizes the importance of chemical mixtures or cocktails in interacting with animals, rather than a single compound.” increase.

Scientists still don’t know when this particular cat’s behavior first evolved. In previous studies, researchers found that leopards and jaguars rub their heads against paper soaked in nepetalactol, much like domestic cats. This finding suggests that this behavior, which utilizes the insect repellent properties of certain plants, may have evolved in distant cat ancestry.

“I think it’s very interesting how cats developed this innate behavior of protecting themselves,” he says. Nadia Melo, A chemical ecologist at Lund University who was not involved in the study. She points out that other mammals are also at risk of similar diseases from insects. “But this is not seen in dogs that are clearly also affected by mosquitoes.”

Catnip and silver vine can also help protect humans from insects. The mosquito species used in this study infect cats and dogs with roundworms and also spread many human viruses such as dengue and chikungunya.And of Melo Previous research It suggests that other mosquitoes are likely to have similar reactions. “I think all mosquitoes react in much the same way,” she says.

Therefore, chemicals from catnip and silver vine may help develop safer and more effective insect repellents for human use. It may also have the side effect of attracting cats. “People who don’t like cats or who are allergic to cats shouldn’t use iridoid as a repellent,” Miyazaki wrote in an email.