How Cats Identify Each Other by Smell: Cat Urine Contains a Unique Chemical Signature
Cats can identify one another by the smell of their urine, and new research has revealed the chemical “message” behind this remarkable ability. A study published in Current Biology found that each cat produces a distinctive combination of branched-chain fatty acids (BCFAs) in its urine.
These fatty acids may create a stable scent fingerprint that allows cats to recognize individuals, even after a urine marking has partially dried or evaporated. The findings could also help scientists better understand how cats communicate through scent and why certain fat deposits are found in their kidneys.
Many animals recognize members of their species using visual, auditory and chemical signals. Some insects, for example, use chemical hydrocarbons to determine whether another insect belongs to the same colony. Mice can also leave identifying information in their urine through specialized proteins.
Until now, scientists knew less about how mammals create individual scent signatures that remain consistent over time. The new cat urine study provides evidence that BCFAs may be one of the key chemical clues cats use to distinguish familiar animals from strangers.
From the latest videoLive Science
“The way I think about mouse proteins is similar to the human face,” said Michael Sheehan, a neurobiologist at Cornell University who was not involved in the research. “My hunch is that it’s probably branched-chain fatty acids found in cat urine.”
Cats investigate interesting smells using the flehmen response—the familiar open-mouthed expression in which a cat appears to grimace. During this behavior, cats draw odor molecules into the vomeronasal organ, a specialized sensory structure that helps detect pheromones and other chemical signals.
In the study, cats showed the flehmen response less often after repeatedly encountering the same urine sample. Their response increased when researchers introduced urine from a different cat. This suggests that cats learn and remember individual scent signatures rather than reacting to one universal feline pheromone.
“We found it surprising that innate behavior can be so strongly influenced by habituation and learning, rather than simply being a fixed response to a single pheromone,” study co-author Masao Miyazaki, a biomolecular scientist at Japan’s Iwate University, told Live Science.
Branched-chain fatty acids create a feline scent fingerprint
To identify the chemicals responsible for the cats’ reactions, the researchers used high-performance liquid chromatography to separate urine into its individual components. They then presented the separated samples to cats and observed their behavior.
The cats consistently showed a flehmen response when they smelled samples containing small amounts of branched-chain fatty acids. Further analysis showed that every cat had a unique mixture of these compounds.
The researchers also found that the BCFA profiles remained stable for at least 24 hours after a cat left a scent mark. This stability may allow cats to gather information about another animal even after much of the urine has dried or disappeared.
Kidney fat droplets may preserve each cat’s unique odor
The study found BCFAs stored in lipid droplets within the renal cortex, the outer region of the kidney. Scientists have known about these unusual fat droplets in cat kidneys for more than a century, but their biological purpose was previously unclear.
The researchers propose that the droplets may serve as a long-term reservoir for BCFAs. By storing these compounds in the kidneys, cats may be able to maintain a consistent urine scent profile despite changes in diet, health or metabolism.
Big cats, including lions and tigers, also have branched-chain fatty acids and lipid droplets in their renal cortex. However, the types and quantities of BCFAs differed between species, suggesting that these scent-producing traits may have changed during feline evolution.
“We now want to understand how these lipid droplets are formed, maintained, mobilized and associated with secretion into the urine,” Miyazaki said. “We are also very interested in whether disruption of these processes contributes to chronic kidney disease in cats.”
Source: www.livescience.com