Thirteen branched-chain fatty acids, mixed in proportions that differ from one cat to the next, appear to give every domestic cat its own chemical signature in urine. A team led by Professor Masao Miyazaki of Iwate University in Japan reports that other cats notice the difference, and that a cat which has already smelled a given animal’s urine loses interest in it, even when the gap between encounters runs to months.
The work, with collaborators in Germany and Spain, was published in Current Biology and also points to an unexpected source for the signature: the cat’s kidney. It may eventually matter for managing household odor and for tracking rare wild felids without ever seeing them.
Thirteen fatty acids and what they encode
According to the ScienceDaily summary of the study, the scientists “identified 13 branched-chain fatty acids (BFAs)” in cat urine. The combination and relative amounts of those compounds varied between individual cats yet stayed fairly consistent within each cat across different collection dates; the team describes the mix as a stable chemical individuality for each animal. Shota Ichizawa is listed first among 17 authors, a group that includes Stefan Schulz and Masako Izawa alongside Miyazaki, and the release lists the Japan Society for the Promotion of Science as funder and declares no conflicts of interest.
The authors found no earlier reports of these particular compounds in the excretions or secretions of any mammal, according to the release distributed through EurekAlert.
Relatedness shows up in the chemistry as well. Related cats generally had more similar BFA patterns, which makes the signature partly inherited, though the release notes that individual differences persisted even inside a family. Samples soaked in urine and kept at 25 degrees Celsius held comparatively stable profiles for at least 24 hours, and the semi-volatile acids evaporate more slowly than many other odor compounds so the profile does not vanish quickly after a cat leaves.
How the cats showed that they remember
Chemistry alone does not prove a signal is read, so the team watched behavior. Cats sniffed a given urine less as the same sample was presented repeatedly and sniffed more when urine from a different cat appeared, the pattern that indicates the animals distinguish the two. The reduced response to familiar urine lasted “even after gaps lasting months,” the ScienceDaily account reports, and the paper in Current Biology (volume 36, issue 17) carries the full data.
A second behavior pointed the researchers toward the molecules. Cats showed the flehmen response, a behavior the researchers used to guide the search, more often toward unfamiliar urine than toward their own, and the response faded with repeat exposure and returned with a new cat’s sample. Miyazaki said the team used the flehmen response “as a clue to identify urinary molecules that may contribute to individual scent recognition.”
In a final test, the team controlled for other lipids and changed only the donor-derived BFA fraction. Cats that had grown used to one sample sniffed again, showing they can detect differences in the BFA mix alone.
A kidney reservoir that keeps the signal steady
The paper’s title names the proposed source, a kidney reservoir. BFAs turned up in the kidney but not in the other tissues examined, where they sit among neutral lipids inside lipid droplets in the renal cortex. Cat kidney lipid droplets have been documented for more than a century, and their purpose was unknown. Miyazaki said that “why cats have so many of them has remained a mystery,” and the study’s suggestion is that “one of their functions may be to support a stable chemical signature in urine.”
The release adds a reading of why that would matter: the droplets may act as a store that buffers changes from diet or physiology, helping keep the signature steady. That interpretation is the authors’ proposal, not a demonstrated mechanism.
The same compounds and droplets were detected in lions, tigers, leopards, jaguars, lynxes and the Iriomote cat, with profiles that differed by species. The Iriomote cat and the Tsushima leopard cat also differed from each other. An earlier preprint of the work on bioRxiv reported analysing urine from 26 Iriomote cats and 17 Tsushima leopard cats, and gave ten domestic cats as the source of 24 urine samples. The preprint’s own methods section is inconsistent about the total number of cats, and neither the ScienceDaily page nor the EurekAlert release states a sample size, so those figures should be read as preliminary.
Several limits apply. Whether wild felids use these acids to recognize one another has not been tested. The release describes the work as basic research with no immediate product, and lists three possible uses: better ways to manage cat urine odor, insight into why lipid accumulation in the kidney is normal in some contexts and linked to disease in others, and non-invasive monitoring of rare wild cats using urine left in the environment, if BFA profiles can reliably identify individuals across repeated samples. Whether BFA profiles can reliably identify individuals across repeated samples is the condition the release attaches to the conservation use, and it remains untested.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
More from Morning Overview
- Lake Powell sank to a record 3,517 feet, nearing the level that stops Glen Canyon Dam’s turbines
- Seven of Earth’s nine planetary boundaries are breached, and all seven are worsening
- The NSA says three phone features should be off whenever you aren’t using them
- Hurricane Hunter radar shows four warning signs that a tropical cyclone is about to strengthen, a University of Miami study found
