For a lesson in euphoria, just look at a domestic cat curled up on a silvery vine branch. When offered a cut of the plant, which contains chemicals similar to those found in catnip, most domesticated cats purr, drool and squeeze their faces into intoxicating leaves and stems, and then pass out in a state of catatonic ecstasy.
But ecstatic running may not be the only reason why cats migrate to these plants, new research suggests. Compounds mixed with plants like silver vine and catnip can also help cats ward off mosquitoes by equipping them with a DIY pest repellent that is much more fun to apply than an oily layer of DEET.
Other articles have pointed to the deterrent effects of catnip insects and similar plants. But the new study, published Wednesday in the journal Science Advances, is the first to establish a direct link between plants and their protective effects on cats.
“It’s a really interesting observation, that such well-known behavior can have this unappreciated benefit for cats,” said Laura Duvall, a mosquito researcher at Columbia University in New York who was not involved in the study.
Botanically speaking, catnip and silver vine are distant cousins. But both contain iridoids, a set of chemicals that seem to tickle cats’ pleasure circuits.
To identify the evolutionary roots of this feline-plant connection, a team of researchers led by Masao Miyazaki, a biochemist and veterinary scientist at Iwate University in Japan, surrounded a collection of cats – some domestic, some wild – and monitored their responses to a iridoid extracted from the silver vine, which thrives in many mountainous parts of Asia.
Receiving pieces of paper dosed with iridoid, most cats began to roll and scrub ritualistically. Some cats were so eager to get involved with the compounds that they climbed the sides of their cages – some of which were nearly six feet tall – to anoint themselves with paper dipped in chemicals attached to the ceiling.
The chemical appeared to have a similar influence on large cats in zoos, including a leopard, two jaguars and two bobcats.
After observing the cat’s cavorts, Dr. Miyazaki and his colleagues were sure that the chemicals were bringing some benefit. Following clues from previous studies on the insect repellent qualities of catnip, the researchers rubbed silver vine iridoids on the heads of several domestic cats, or allowed the felines to apply the substance themselves, and put the animals within reach. dozens of thirsty mosquitoes. The insects pinched the faces of un anointed cats, but they largely despised the cats that went crazy over the vines.
The origins of the so-called catnip response have plagued animal behaviorists for years. Experts had previously suspected a link to playful or mating behaviors, which also induce episodes of frantic feline scrolling. But the new findings suggest that cats, which can contract heartworm from mosquito bites, may also reap some medicinal benefits from their botanical fights, said Mikel Delgado, a feline behavior expert at the University of California at Davis who was not involved in the study. It would not be the first example of an animal smearing itself with plant compounds to improve health.
Still, the case has not yet been closed, said Sarah O’Connor, a biochemist at the Max Planck Institute for Chemical Ecology in Germany who studies catnip but was not involved in the new study. There may still be other reasons why cats go crazy for iridoids. And researchers are still unsure why chemicals make cats, but not other animals like dogs or mice, so nervous.
An obvious next step would be to see if cats attracted to plants do better in nature than their indifferent counterparts to iridoids, said O’Connor. Natural mosquito repellent “is a convincing explanation,” she said. “I think it needs more evidence to prove it.”
Until the insect repellent qualities of catnip and silver vine are clearer, Delgado said he would not recommend plants as natural repellents for cats or humans.
Dr. Miyazaki was more optimistic. In a unique experiment, he spread iridoids on his arm and stuck him in a mosquito cage. Insects avoided – but feasted on an untreated limb. “We hope to use it for humans in the future,” he said.