Cats’ Strange Reactions to Catnip Make It a Better Insect Repellent

Anyone who’s seen a cat experience catnip knows it drives them a little wild — they rub in it, roll over it, chew on it, and lick it aggressively. This plant and its Asian counterpart, silver vine, are widely believed to have intoxicating properties, but that may not be the only reason cats rub and chew on plants so enthusiastically. Researchers in Japan have found that when cats damage catnip, much higher amounts of potent insect repellents are released, indicating that cats’ behavior protects them from parasites. This study appears in the journal iScience June 14.

Cats’ reaction to catnip and silver vine is so pervasive that lead author Masao Miyazaki, an animal behavior researcher at Iwate University, had to know what was going on. “Even in the famous musical Cats, there are scenes where you see a cat intoxicate another cat with catnip powder,” he says. Miyazaki began his career in veterinary medicine and became interested in how chemicals, such as pheromones, drive instinctive behaviors in pets.

Catnip and silver vine leaves contain the compounds nepetalactol and nepetalactone, iridoids that protect plants from pests. To see how the behavior of cats affected chemicals released by plants, Miyazaki worked with chemists at Nagoya University. “We found that physical damage of silver vine by cats promoted the immediate emission of total iridoids, which was 10 times higher than that of intact leaves,” Miyazaki says.

Not only were more iridoids released, but their composition changed in a way that seemed to encourage the cats. “Nepetalactol accounts for more than 90% of total iridoids in intact leaves, but this drops to around 45% in damaged leaves because other iridoids increase dramatically,” Miyazaki says. “The altered iridoid mixture corresponding to the damaged leaves promoted a much more prolonged response in cats.”

In previous work, Miyazaki and his team have shown that these compounds effectively repel Aedes albopictus mosquitoes. Now the team has shown that when cats damage plants by rubbing, rolling, licking and chewing, the repellent properties are even more effective. The diversification of iridoids in the damaged silver vine leaves makes it more repellent to mosquitoes in low concentrations.

To test whether felines reacted specifically to these compounds, cats were given dishes containing pure nepetalactone and nepetalactol. “Cats show the same response to iridoid cocktails and natural herbs, except for chewing,” says Miyazaki. They lick the chemicals off the plastic dish, rub and roll on it.”

“When iridoid cocktails were applied to the bottom of dishes which were then covered with a perforated plastic lid, cats continued to lick and chew even though they could not come into direct contact with the chemicals,” says Miyazaki. . “This means that licking and chewing is an instinctive behavior elicited by olfactory stimulation from iridoids.”

Next, Miyazaki and his team want to figure out which gene is responsible for cats’ reaction to catnip and silver vine. “Our future studies promise to answer the main remaining questions, namely why this response is limited to Felidae species and why some cats do not respond to these plants,” says Miyazaki.

This research was funded by JSPS KAKENHI, Suntory Foundation for Life Sciences, and Japan Science Society Sasakawa Scientific Research Grant.

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