Cats May Recognize Each Other by the Fatty Acids in Their Urine, Study Finds

Cats likely tell one another apart by detecting unique types and ratios of fatty acids in urine, according to an international research team that includes members from Japan's Iwate University. The findings, led by Professor Masao Miyazaki, were published in the journal Current Biology.

The researchers focused on the Flehmen response — the open-mouthed grimace cats make while smelling urine or other odorous substances — which typically occurs when a cat encounters the smell of an unfamiliar individual. The team identified 13 types of branched-chain fatty acids in cat urine and found that the specific types and ratios present vary from one cat to another. Because these fatty acids are semivolatile, meaning they evaporate slowly, the odor cues they carry remain detectable for an extended period.

The researchers also found that these lipids, including the fatty acids, are stored as lipid droplets inside the kidneys. Similar urine fatty acids and kidney lipid droplets were found in other feline species, including lions, tigers, leopards and the Iriomote cat, a wild cat native to Japan. The fatty acid compositions differed between species, a diversity the researchers say likely developed over the course of feline evolution.