This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Many animals obtain information about others from scent marks left in the environment, including urine. Because these marks remain after the sender has left, they allow animals to communicate across space and time.
But odor molecules evaporate, degrade and change after release. How, then, can a scent mark continue to convey reliable information about who left it? An international research team from Japan, Germany and Spain, led by Iwate University, has identified a candidate chemical system that may help domestic cats maintain stable individual information in urine odor.
Combining behavioral experiments with chemical analyses, the researchers discovered 13 branched-chain fatty acids (BFAs) whose combinations and relative proportions differed among cats but remained relatively stable within the same individual. Cats could also discriminate between donor-specific BFA compositions when other urinary lipid components were experimentally controlled. The findings suggest that BFAs are strong candidates for carrying durable individual information—a chemical "calling card"—in cat urine.
The study will be published in Current Biology. The researchers first confirmed that cats can distinguish urine odors from different individuals. When the same urine was presented repeatedly, cats gradually spent less time sniffing it, but sniffing increased again when urine from another cat was introduced.
Reduced responses to previously encountered urine odors could still be observed after intervals of months, suggesting long-term memory of urine scents. The team then focused on the flehmen response, the distinctive open-mouthed expression familiar to many cat owners. Cats showed flehmen more frequently toward unfamiliar urine than toward their own urine, and the response decreased with repeated presentation of the same urine but increased again when urine from another individual was introduced.
"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, who led the research project. This behavior-guided approach led to a urinary lipid fraction containing unusual BFAs. The researchers identified 13 BFAs and, based on their literature survey, found no previous reports of the same compounds in mammalian excretions or secretions.
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