MORIOKA -- Cats have long been known to love silvervine, and a research team in Japan has found that the attraction may be for a practical reason -- the plant helps repel mosquitoes.
The results of the joint study by a group comprising researchers at Iwate University in northern Japan, led by professor Masao Miyazaki, and researchers at Nagoya University in central Japan, led by professor Toshio Nishikawa, as well as scientists from other universities, could be used to develop a new repellent. As it had previously been unclear why cats display such responses, a researcher said, "It's an important answer to a long-standing mystery."
The study revealed that a substance known as nepetalactol in silvervine elicits the characteristic response in cats and is effective at repelling mosquitoes, which transmit parasites, etc. In experiments, the number of mosquitoes that bit cats which had nepetalactol applied to their bodies was roughly half the number that did so to cats to which the substance had not been applied.
During a news conference held at Iwate University on Jan. 19, professor Miyazaki said they had conducted experiments using 25 cats kept at his laboratory, adding, "I felt sorry for the cats being used for the experiments, so in the end I used my arms for the study." Miyazaki put them into containers with mosquitoes for about 30 minutes. One arm without nepetalactol on it was bitten by mosquitoes, while the other arm with nepetalactol applied was not.
Miyazaki named the cat that was most reactive to silvervine "Science," after a famous journal. As the moods of cats were also an important part of the experiments, he cleaned inside their cages every morning and evening for an hour, he said.
The biological significance of cats' behavior caused by silvervine had been unclear. In the research, they confirmed for the first time that when cats react to silvervine, the blood level of a substance activated in the brain when cats feel happy rises. "It's a reaction that is seen only in felids such as leopards," Miyazaki said. He believes that the reaction is associated with the behavior of felids that hunt while hiding in bushes where there are many bugs.
The group's research was published in the U.S. scientific journal Science Advances.
(Japanese original by Ikuko Ando, Morioka Bureau)