Cats’ reaction to catnip – and its Asian counterpart silvervine – is truly a sight to be seen. Our household pets start aggressively rolling, rubbing, chewing, and licking it like they have been possessed by these plants’ taste and aroma. A team from Iwate University has recently published a study giving insight into why this intoxicating relationship evolved and how the chemical properties of plants cause this reaction.
Both catnip and silvervine are filled with protecting chemicals called iridoids that deter pests. Previous studies have proved these compounds to be effective in repelling Aedes albopictus mosquitoes, which in turn, lowers the plant’s chances of disease and being consumed by insects.
The team suspected that there may be an interesting relationship here between these molecules and the intense feline response. They hypothesized that the reason cats react like this is that iridoids also provide them with advantageous protection from pests. To investigate this connection further, behavioral and chemical experiments were set up.
The team found that when the plant leaves and stems are broken, a 10-fold increase of iridoids is emitted into the surrounding environment. This means cats’ aggressive physical response is likely to be driven by their reward of a repellent perfume.
Comparison studies were also set up, where cats were observed reacting to both an intact plant and dishes of these insect-repelling chemicals. “Cats show the same response to iridoid cocktails and natural plants except for chewing. They lick the chemicals on the plastic dish and rub against and roll over on the dish,” explains lead author Masao Miyazaki.
“When iridoid cocktails were applied on the bottom of dishes that were then covered by a punctured plastic cover, cats still exhibited licking and chewing even though they couldn’t contact the chemicals directly,” says Miyazaki. This result implies that chewing behavior is encouraged when the cat hasn’t made direct contact with the iridoids, possibly as an automatically triggered mechanism to encourage the breaking of the plant.
Overall, the study shows that the licking, chewing, and rubbing of catnip are instinctive behaviors of cats in response to smelling iridoids, probably gained as an evolutionary protective response against pests. These experiments have helped forward knowledge in understanding the inner workings of our feline friends, plus, provide pet owners with a simple way to protect their cats from pests and disease.
Source study: iScience – Domestic cat damage to plant leaves containing iridoids enhances chemical repellency to pests