A multinational research team led by Iwate University has identified a potential chemical basis for how cats recognize each other through urine marking. The study, set to appear in Current Biology, focuses on branched-chain fatty acids (BFAs) that appear to function as individual chemical identifiers in feline urine.
Initial behavioral experiments established that cats can distinguish urine samples from different individuals over extended periods. When researchers repeatedly presented the same urine sample, cats gradually reduced their investigative sniffing behavior. However, when urine from a different cat was introduced, their interest renewed immediately. Cats demonstrated the ability to recall specific urine odors even after gaps spanning multiple months, suggesting long-term olfactory memory. Researchers also tracked the flehmen response, a characteristic facial expression cats display when investigating certain scents, and found it occurred more frequently with unfamiliar urine than familiar samples.
Using cats’ behavioral responses as a guide, the research team identified 13 previously unreported BFAs in feline urine. Each cat displayed a unique combination and proportion of these compounds, with individual profiles remaining relatively consistent across multiple sampling occasions. The genetic relationship between animals influenced BFA patterns, with related cats showing greater similarities, though each cat maintained a distinguishable individual signature. The fatty acids themselves proved relatively stable, remaining intact in stored urine samples for at least 24 hours at standard temperatures, contrasting with the rapid degradation of many volatile odor molecules.
Direct testing confirmed that cats could perceive differences in BFA compositions when researchers controlled for other lipid components. The investigation also revealed an unexpected connection to a century-old mystery surrounding feline kidney biology. Researchers detected BFAs stored in lipid droplets within the renal cortex, structures that have been observed in cat kidneys since the 1800s but whose function remained unknown. This storage mechanism may help maintain stable chemical signatures despite fluctuations in diet or physiology.
Extending beyond domestic cats, the research team found BFA-related compounds and associated kidney structures in multiple wild felid species, including lions, tigers, leopards, and jaguars. However, the specific BFA profiles differed among species, suggesting the chemistry has diversified throughout feline evolutionary history.
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