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Cat communication is driven by bacteria in their anal glands

A study from UC Davis has revealed fascinating new details about cat communication, focusing on the role of scent and bacteria in their interactions. The experts found that domestic cats send signals to each other using odors derived from bacteria living in their anal glands. 

The research was conducted by Connie Rojas, a postdoctoral researcher, and Professor Jonathan Eisen from the UC Davis Department of Evolution and Ecology and Genome Center.

Animal communication

Many different animals use scents to communicate with each other. This form of communication is especially important in the animal kingdom.

Some mammals mark their territory with scents. This serves as a warning to others of their presence and claims over an area.

Scents play a crucial role in the mating behaviors of various mammals. They can indicate when an individual is ready to mate or help in selecting a genetically compatible mate.

Animals express fear, aggression, or other emotions through scents. This is often a way to communicate danger or assert dominance. Scents can also help mammals identify each other. 

Microbes and odor

The UC Davis study adds to a growing body of research on the relationship between microbes and odor in mammals.

“Many mammals rely on volatile organic chemical compounds (VOCs) produced by bacteria for their communication and behavior, though little is known about the exact molecular mechanisms or bacterial species that are responsible,” wrote the study authors.

Focus of the study

Rojas led a detailed three-part investigation into the anal gland secretions of domestic cats, utilizing advanced techniques like DNA sequencing, mass spectrometry, and microbial culturing. The goal was to understand the chemical composition of these secretions and the microbes responsible for their production.

The subjects of the study were 23 domestic cats, patients at the UC Davis Veterinary Medical Teaching Hospital, who were undergoing elective procedures like dental cleaning. Their participation was authorized by their owners through written consent.

Significant findings

The team discovered a highly variable microbiome in the cats’ anal glands. Predominantly, five bacterial genera – Corynebacterium, Bacteroides, Proteus, Lactobacillus, and Streptococcus – were found. 

However, there was considerable variation in the microbial makeup among individual cats. Notably, older cats tended to have a different microbiome compared to younger ones. The experts also observed variations in obese cats, although the sample size was too small for definitive conclusions.

Living environment 

“Interestingly, we did find evidence that the microbiome functional repertoires in the anal gland were associated with host living environment; cats that lived indoors had microbiome functions that were not identical to cats that had outdoor access,” wrote the study authors. 

“It is thought that cats with outdoor access are more likely to be infected with parasites than indoor-only cats but may have more exposure to natural enrichment and mental stimulation. Conversely, cats that have an indoor-only lifestyle may experience reduced physical activity, greater food consumption, and less natural enrichment.” 

“Nonetheless, it is not clear how these lifestyle differences and contact with the outdoors could be linked to functional differences in the anal gland microbiome.”

Anal gland microbiome 

The researchers said it is important to acknowledge that another factor and source of variation in anal gland microbiome profiles could be the perianal skin surrounding the gland itself and the rectum. 

“Due to their physical proximity and host grooming behaviors, it is possible that there are microbes in the anal gland that came from the skin or rectum.”

Organic compounds 

Further analysis of the chemicals in the anal glands revealed the presence of hundreds of organic compounds. Genetic analysis suggested that the residing bacteria are producing these organic compounds – including aldehydes, alcohols, esters, and ketones – which form the basis of cats’ unique scents. 

While these odors are mostly imperceptible to humans, they play a crucial role in cats’ social behaviors, such as marking territory, attracting mates, and repelling rivals.

More about cat communication

Cat communication is a complex and multifaceted aspect of feline behavior, encompassing a variety of vocalizations, body language, and scent signals. Understanding these different modes of communication can provide deeper insights into the world of cats.


Cats use a range of vocalizations to communicate. For example, cats typically use meows to communicate with humans. Kittens meow to get attention from their mothers, but adult cats usually reserve meowing for human interactions.

Purring often signifies contentment and can also be a comfort-seeking behavior when a cat is nervous or in pain. Hissing and growling sounds indicate fear, aggression, or territoriality.

Cats may chirp or chatter when a cat is watching birds or other prey animals, possibly expressing frustration or excitement.

Body language

Cats convey much through their body posture, tail movements, ear positions, and facial expressions.

  • Tail position: A raised tail generally indicates happiness or confidence, while a tucked tail suggests fear or submission. A twitching or lashing tail can signal irritation.
  • Ear movements: Forward-facing ears show interest, while flattened ears may indicate fear, aggression, or irritation.
  • Whiskers and eyes: Forward-facing whiskers and dilated pupils can indicate excitement or playfulness, while constricted pupils might suggest aggression.

Scent marking

As highlighted in the UC Davis study, scent plays a vital role in cat communication. Cats have scent glands in various body parts, including their cheeks, paws, and base of their tails. They use these to mark territory, identify familiar objects, or signal their reproductive status.

  • Cheek Rubbing: When cats rub their faces on objects (or people), they are marking them with their scent, claiming them as familiar or safe.
  • Scratching: Cats also leave scent marks from their paws when they scratch surfaces, serving both as a visual and olfactory territorial marker.


Kneading is a behavior cats retain from kittenhood, where they would knead their mother’s belly to stimulate milk flow. In adulthood, it’s often associated with contentment and may also serve as a way to mark territory with scent glands in their paws.


Cats groom themselves for cleanliness, but when they groom other cats (or humans), it’s a sign of affection and bonding, also known as allogrooming.

The study is published in the journal Scientific Reports.

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