Even the most reserved cats can get excited by a few catnip leaves.
Our feline friends are infected by silver vine (or matatabi in Japanese) that induces similar plant-induced euphoria. Although the cat's response looks fun, scientists have not yet been able to determine if there are other benefits.
This week's iScience research suggests that cats can damage silver vine or catnip leaves. These plants emit more chemical compounds, which repel mosquitoes. The leaves can be used as a natural insect spray. Cats will also be able to chew the leaves. The research was conducted by researchers at Japan's University of Iwate. They have been studying cats' interactions between silver vine and catnip for many years.
However, cats do not roll around in the leaves as a part of their response to the plants. Masao Miyazaki of Iwate University, an animal behaviorist, and the author of the study, said that cats engage in four basic behaviors when they are given catnip and silver vine. These include chewing, licking and rolling. Miyazaki stated that rolling and rubbing were important for transferring iridoids, which are chemicals that activate the cat's endorphine rush to cat fur. This repels mosquitoes. Although rubbing silver vine leaves in a cat's manner of spraying bugs is one explanation, it does not explain why cats also lick and chew them.
The researchers examined what happens to the chemical levels of leaves when they are damaged by cats in a new study. The researchers first collected intact leaves from the silver vine, as well as those that were chewed by cats or crumpled by hand. The chemical analysis revealed that both cats and humans had caused the leaves' emission of various iridoids to rise. The chemical mix in the leaves with damage was less dominant by one chemical and had instead a greater balance of five chemicals.
These chemical cocktail were then tested to see how the cats and mosquitoes responded. Cats spent more time rolling on damaged silver vine leaves than they did with the intact ones. Researchers created chemical cocktails from these leaves that cat lovers enjoyed again.
Even though the levels of silver vine's main iridoid, nepetalactol were identical, the cats preferred the well-balanced mix of iridoids to the simpler one. It was previously believed that cats were attracted to nepetalactol. However, this new research revealed that something more appealing about the combination of chemicals was found. Reiko Uenoyama (a graduate student at Iwate University) said, "I was really amazed that the combination of the iridoid compound enhanced the feline reaction."
Silver vine was able to diversify its chemical profile in response to cat-inflicted harm, but catnip didn't. Researchers repeated their experiments with catnip, and came up with very different results. The main iridoid compound in catnip, nepetalactone, is the main one. This remains true regardless of whether or not there has been any leaf damage. Cats that chew catnip will increase their nepetalactone emissions by eating the leaves.
Crumpled catnip leaves still attracted cats, and was more repellant to mosquitoes than the other reaction to damage. In this instance, however, the response was due to higher levels a single chemical. Comparing the plants, it was found that a larger amount of catnip cocktails was required to trigger the same reaction from cats and mosquitoes than a small amount of silver vine cocktail. Because of the higher levels of chemicals that catnip plants emit, catnip is just as appealing to cats than silver vine leaves.
Scientists aren't sure why small amounts of complex chemicals can trigger such strong reactions. Scientists are still unsure why complex mixtures of chemicals trigger responses in animals. Miyazaki says, "Unfortunately,"
Scientists still don't know when this cat behavior originated. Researchers found that jaguars and leopards rub their heads on nepetalactol-soaked papers just like domestic cats. This suggests that this behavior, which takes advantage of the insect repellant properties of certain plants, may have been inherited from a distant feline ancestor.
Nadia Melo, a chemical ecologist at Lund University, says that "I find it so fascinating how cats have developed this instinctive behavior of defending themselves such as this way." She points out that insects can cause similar diseases in other mammals, but this is not the case for dogs, who are also susceptible to them.
Silver vine and catnip could also be beneficial in protecting people from insect bites. This study shows that roundworms are transmitted to dogs and cats by the mosquito species used. It also spreads many viruses such as dengue and chikungunya. Melo's research has shown that other mosquitoes may have similar reactions. She says, "I believe all mosquitoes would respond pretty much the same."
The chemicals in catnip, silver vine and other herbs could be used to create safer and more effective insect repellants that can be used by humans. They might also attract cats. Miyazaki writes in an email that "if someone doesn't like cats or has allergies to cats, they shouldn't use iridoids for repellents!"