Every cat leaves a personal chemical signature in its urine, and other cats can tell those signatures apart. A team led by Iwate University in Japan found that the signature is a mix of 13 unusual fatty acids. The work is published in Current Biology.
Most smells in urine change quickly once it is left behind. So what could carry a lasting message? These fatty acids, called branched-chain fatty acids, evaporate slowly and stay stable.
How the cats showed it
The researchers first gave cats the same urine sample several times. The cats sniffed less each time, a sign that they recognized it. A sample from a different cat made them curious again.
The team then kept everything in the samples equal except the mix of these 13 fatty acids. The cats still noticed the difference. Each cat had its own mix, and that mix stayed about the same over time.
An old puzzle in the kidney
Cat kidneys are full of tiny fat droplets. Scientists have known about them for more than a century without knowing why they are there. The study found the same fatty acids in those droplets. The authors suggest the droplets work as a store that keeps each cat's scent steady, even when its food changes.
Lions, tigers, leopards, jaguars and lynxes carry these fatty acids too, each species with its own pattern.
