Scientists Discover How Cats Communicate

Most animals communicate using scent, but scientists have now uncovered that each cat's signal is based on the type of bacteria living in their butts.

Every cat has its own unique cocktail of bacteria living in its anal glands, which produce the hundreds of compounds that make up a cat's scent and therefore the messages it sends to other cats, according to a new study in the journal Scientific Reports.

Cats mark their territory, attract mates and warn away enemies using their scents, which are comprised of a bouquet of volatile organic compounds, such as aldehydes, alcohols, esters and ketones. The scientists discovered that these compounds may vary with the species of bacteria living in a cat's anal gland microbiome.

"All we want to know right now is, can we see if there is a connection between what microbes are present in the anal sac of cats and what volatile compounds are produced. Our study here suggests the answer is yes but it is only a weak relationship with the data we have right now," Jonathan A. Eisen, co-author of the paper and professor of microbial ecology and evolution at the University of California, Davis, told Newsweek.

"We found a correlation between which microbes were present and specific volatile compounds found in the samples. And we have some candidate bacteria that we have data for now that may be the ones making these volatile compounds," he said.

The authors performed a three-part study on 23 domestic cats—with their owners' permission—taking microbial cultures of the cats' anal glands, DNA sequencing the bacteria found and performing mass spectrometry on the gland secretions.

They found that five genera of bacteria—Corynebacterium, Bacteroides, Proteus, Lactobacillus and Streptococcus—dominated across all the cats, but that each cat had an individual microbial makeup. These differences were more pronounced between older and younger cats.

The exact reason for these differing microbiomes is unknown, but may be driven in part by the diet of the cat, its health and its living environment.

"This is really early work and it is suggestive that (1) microbes help produce these odors and (2) there are likely many many microbes involved," Eisen said. "And if this is true it would seem almost guaranteed that different cats will produce different odors since they will certainly have different relative amounts of microbes that do this in their glands."

"What I am personally most interested in is the role(s) microbes might play in odor and especially social communication in the whole group of the 'Felidae' including all the wild cats," he said. "We know that many animal species do scent marking with specialized scent glands and that in some cases this allows members of a group to recognize individuals by their unique odors. Prior work by others has suggested that for some animals (e.g., hyenas) the animal makes some microbial food that it secretes into a specialized gland or region and then microbes feed on this and convert it into volatile compounds that become the "unique" scent for an individual."

The researchers hope to figure out exactly what kind of role the microbes play in the production of these odors, and also if the animals themselves somehow influence which microbes are involved, or if it's a random process.

"If it is not random—[we want to know] how do the microbes and the host interact and what determines which microbes are there and also then how do the microbes actually influence the odors that are produced," Eisen said.

As for what the cats are truly saying to each other in these messages, we still have no idea how to interpret the chemical codes.

"We are really just starting this work so we are not at the point where we are even starting to think about the messages cats might be sending with their scents," Eisen said.

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