For a lesson in euphoria, a house cat is just what you need. When the plant is domesticated, which contains chemicals similar to those found in catnip, most domesticated cats purr, drool, and flatten their faces into their heady leaves and stems, and then disappear in a state of catatonic bliss.
But the ecstatic onslaught may not be the only reason cats flock to these plants, new research shows. Compounds laced in plants like silver vines and catnip can also help cats repel mosquitoes by adding a DIY pesticide that is far more fun to use than a greasy layer of DEET.
Other publications have pointed to the insect repellent effects of catnip and similar plants. The new study, published Wednesday in the journal Science Advances, is the first to establish a direct link between the plants and their protective effects on cats.
“It’s a really interesting observation that such known behavior could have these neglected benefits for cats,” said Laura Duvall, a mosquito researcher at Columbia University in New York who was not involved in the study.
Botanically, catnip and silver vine are distant cousins. But both contain iridoids, a number of chemicals that seem to be extremely tickling in cats’ pleasure circles.
To pinpoint the evolutionary roots of this connection between plants and cats, a team of researchers led by Masao Miyazaki, a biochemist and veterinary scientist at Iwate University in Japan, put together a menagerie of cats – some domestic cats, other wild cats – and put together their reactions to one Cat monitors iridoid from silver vine that thrives in many mountainous parts of Asia.
Most cats presented with iridoid-dose scraps of paper initiated ritualized rolling and rubbing. Some cats were so eager to study the compounds that they climbed the sides of their cages – some of which were three feet high – to anoint themselves with chemically soaked paper on the ceiling.
The chemical appeared to have a similar impact on big cats in zoos, including a leopard, two jaguars, and two lynxes.
After Dr. Miyazaki and his colleagues had observed the cats’ deceptions, they were certain that the chemicals would bring some benefit. Based on previous studies of catnip’s insect repellant properties, the researchers next rubbed silver vine iridoids on the heads of several domestic cats or let the cats apply the substance themselves and put the animals within reach of dozens of thirsty mosquitos. The insects nibbled on the faces of unconscious cats, but for the most part slowed down the cats who had become gaga for the vines.
The origins of the so-called catnip reaction have pestered animal behaviorists for years. Experts had previously suspected a connection with play or mating behavior, which also causes attacks of frenzied cat rolling. However, the new evidence suggests that cats who can become infected with heartworms from mosquito bites may also get some medicinal benefits from their botanical struggles, said Mikel Delgado, an expert on feline behavior at the University of California at Davis, who does not the infection was involved in study. It wouldn’t be the first example of an animal to smear itself with plant matter to improve health.
The case is still ongoing, 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 could be other reasons cats go crazy about iridoids. And researchers still aren’t sure why the chemicals are making cats so nervous but not other animals like dogs or mice.
An obvious next step would be to see if cats attracted by the plants do better in the wild than their iridoid-indifferent counterparts, said Dr. O’Connor. Natural mosquito repellent “makes a compelling statement,” she said. “I think it takes more evidence to prove it.”
Until the repellent properties of catnip and silver vine are clearer, said Dr. Delgado, she wouldn’t recommend the plants as natural repellants for either cats or humans.
Dr. Miyazaki was more optimistic. In a one-off experiment, he hit his arm with iridoids and put it in a mosquito cage. The insects steered clearly – but they ate on an untreated limb. “We hope to be able to use it for people in the future,” he said.