Secret 'messages' in cat pee let felines identify each other — and scientists just cracked the code

Scientists have finally decoded the hidden messages in cats' urine, revealing how felines identify one another. The key lies in the scent marks they leave behind, which contain unique chemical signatures called branched-chain fatty acids (BFAs). These BFAs are produced in the cats' kidneys and are maintained by unusual fat droplets called lipid droplets in the renal cortex.

Cats show a behavior called the flehmen response, an innate reaction that draws these chemicals into their vomeronasal organ, when they encounter familiar urine samples. However, the response intensifies when they come across urine from a new cat. Each cat has a distinct mix of BFAs in its urine, which can remain stable for at least a day after the mark is left.

This suggests that BFAs can provide information about the cat that left the mark, even after the rest of the urine has evaporated. The study, published in the journal Current Biology, also found that similar processes occur in large cats like lions and tigers. Further research is being conducted to understand how these lipid droplets are formed, maintained, and linked to urine secretion, as well as whether disruptions to these processes could contribute to chronic kidney disease in cats.