A collaborative study by scientists from Japan, Germany, and Spain has uncovered a chemical mechanism that allows cats to recognize individual peers through urine scent. Led by Iwate University, the research identifies 13 branched-chain fatty acids (BFAs) that function as a stable chemical “calling card,” preserving identity information even as other volatile compounds in urine degrade.
The findings, set to be published in Current Biology, address a long-standing puzzle in animal communication: how scent marks can retain individual identity despite rapid chemical changes after deposition. The discovery also offers a potential explanation for the biological function of lipid droplets in feline kidneys, a phenomenon that has puzzled researchers for over a century.
Confirming Long-Term Scent Memory
Before identifying the specific chemicals involved, the team needed to verify that cats could distinguish between the urine of different individuals. Behavioral experiments revealed that cats habituated to a specific urine sample eventually lost interest, spending less time investigating it. However, their attention was reignited when urine from a novel cat was introduced.
Cats demonstrated remarkable long-term memory, maintaining reduced responsiveness to previously encountered scents even after intervals of several months. Researchers also tracked the flehmen response—a curling of the upper lip used to analyze odors—finding that cats exhibited this behavior more frequently when encountering unfamiliar urine than their own.
“After confirming that cats can distinguish individual urine odors, we used the flehmen response as a clue to identify urinary molecules that may contribute to individual scent recognition,” said Professor Masao Miyazaki of Iwate University.
A Distinctive Chemical Signature
Guided by behavioral cues, the scientists isolated a lipid fraction containing unusual BFAs. They identified 13 such compounds, none of which had been previously reported in mammalian excretions or secretions according to existing literature.
The key to these compounds lies not in their mere presence, but in the specific profile formed by their combination and relative abundance. Each cat possesses a unique BFA pattern that remains consistent over time, even as the volatile components of urine odor shift rapidly after deposition. While genetics influences these profiles—with related cats showing more similar patterns—individual distinctiveness is maintained even among family members.
Testing confirmed that cats can detect these differences. When researchers altered only the BFA fraction of a familiar urine sample while controlling for other lipids, cats resumed investigative sniffing, indicating they perceived the change as significant.
Linking to the Kidney Mystery
The study also shed light on an anatomical enigma. BFAs were detected exclusively in the kidneys, specifically stored within lipid droplets in the renal cortex. Cats are known for having an unusually high number of these droplets, yet their purpose has remained unclear.
The researchers propose that these droplets act as a reservoir, buffering short-term fluctuations caused by diet or physiological changes. This storage system helps maintain a steady chemical signature in urine. “Our findings suggest that one of their functions may be to support a stable chemical signature in urine,” Miyazaki noted, adding that understanding how these lipids are released remains a key question for future study.
Evolutionary Implications Across Felidae
The search extended beyond domestic cats to other members of the Felidae family. Similar BFA-related compounds and renal lipid droplets were found in lions, tigers, leopards, jaguars, lynxes, and the Iriomote cat. However, specific profiles and droplet distributions varied by species and geography, including differences between the Iriomote cat and the Tsushima leopard cat.
This suggests that BFA chemistry is a widespread trait in felines that has diversified over evolutionary time. While the ability of wild felids to use these markers for individual recognition has not yet been proven, the chemistry appears to be a fundamental aspect of feline biology.
Potential Applications
Although currently basic research, the findings may lead to practical applications. Insights into BFA chemistry could improve methods for managing cat urine odor. Additionally, the kidney discoveries might help scientists understand why lipid accumulation is normal in some contexts but pathological in others.
In wildlife conservation, if BFA profiles prove reliable for individual identification, environmental urine sampling could offer a non-invasive tool for monitoring rare felid populations without the need for capture or direct observation.
Wait, does this mean every cat urine sample is essentially a fingerprint? That changes everything about stray tracking.
Finally, a credible explanation for those weird kidney droplets. A century of mystery solved by fatty acids.
I always wondered why my cat stares at my water bowl for five minutes. Now I know she’s reading the news.