Your cat may leave a ‘calling card’ behind when it pees

To humans, a patch of cat urine is generally something to clean up as quickly as possible. To another cat, however, it may contain considerably more useful information.

Scientists have identified a group of unusual chemicals in domestic cat urine that appear to form a distinctive signature for each animal – effectively a chemical calling card that remains relatively stable after the scent is deposited.

The international study, led by researchers at Japan’s Iwate University and published in “Current Biology”, identified 13 branched-chain fatty acids (BFAs) in cat urine.

What mattered was not simply whether those compounds were present, but their proportions: each cat produced its own characteristic combination.

The researchers also found that the profile remained comparatively consistent when the same animals were sampled at different times.

Related cats tended to have more similar profiles, suggesting genetics may play some role, although individual animals could still be distinguished from one another.

A message left behind

Cats rely heavily on scent to gather information about their surroundings and other animals. Urine marking allows that information to remain in the environment even after the animal responsible has moved on.

The puzzle for scientists was how such a scent could continue conveying identity when many of the chemicals responsible for smell evaporate or change over time.

BFAs may provide part of the answer: unlike highly volatile compounds that disappear relatively quickly, the newly identified fatty acids evaporate more slowly.

In laboratory tests, individual BFA patterns remained comparatively stable for at least 24 hours after urine was deposited.

The cats themselves also appeared able to tell those chemical profiles apart. When researchers repeatedly presented the same urine scent, the animals gradually lost interest, but began investigating again when urine from a different cat was introduced.

They could also distinguish samples in which researchers altered the BFA component while keeping other urinary lipids the same.

The clue inside a cat’s kidneys

The research produced another intriguing finding. Scientists traced the BFAs to lipid droplets stored in the renal cortex – structures in cat kidneys that have been known to researchers for more than a century, but whose purpose has remained unclear.

The team suggests these droplets may act as a reservoir, helping stabilise the mix of fatty acids entering the urine despite short-term changes in diet or physiology.

Similar chemical and kidney characteristics were also identified across other members of the cat family, although the experts caution that it has not yet been established whether wild felids use the same system to recognise individuals.

For now, the study offers a striking glimpse into a sensory world humans largely miss. What smells like an unpleasant household accident to us may, to another cat, contain something closer to a nametag or calling card.

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