One cat licking another cat’s rear end is a normal part of feline social behavior. It looks strange (and maybe a little gross) to us, but cats use this area as a rich source of chemical information about each other. In most cases, this behavior is a sign that your cats have a close social bond, though occasionally it can signal a health issue worth paying attention to.
It’s a Form of Social Grooming
Cats who live together and get along will groom each other in a behavior called allogrooming. This mutual grooming most often targets the head and neck, but it can extend to the rest of the body, including the rear. Allogrooming happens more frequently between cats who are “preferred associates,” meaning cats who also sleep near each other, rub against each other, and greet each other nose-to-nose. Cats are more likely to groom relatives than non-relatives, and among unrelated cats, they tend to groom the ones they’ve known longest.
So if your cat is licking your other cat’s backside, it typically means they’re comfortable with each other. It’s a sign of trust and social closeness, not something weird by cat standards.
Cats Read Chemical Information From That Area
There’s a practical reason the rear end gets attention. Cats have two small anal sacs located on either side of the anus, and these glands produce secretions packed with chemical signals. Research published in the Journal of Ethology found that the short-chain fatty acids in these secretions function primarily as individual identification markers. Each cat produces a unique chemical profile, almost like a scent fingerprint. Interestingly, there’s no difference in the chemical profiles between male and female cats, so the information being communicated is more about “who are you?” than “what sex are you?”
These secretions also release onto a cat’s feces for territorial marking, and they may carry information about reproductive state. When one cat licks another’s rear, it’s essentially reading a detailed status update: confirming identity, checking in on health and condition, and reinforcing familiarity.
Maternal Instincts Carry Into Adulthood
This behavior has deep roots in early kittenhood. Mother cats lick the anogenital area of newborn kittens to stimulate urination and defecation. Kittens younger than about three weeks old physically cannot eliminate waste without this stimulation. Orphaned kittens who miss out on it often become constipated.
While adult cats obviously don’t need help going to the bathroom, the instinct to groom this area doesn’t disappear entirely. In multi-cat households, a dominant or nurturing cat may continue this caretaking behavior with other cats, especially ones they’ve known since kittenhood. It’s a holdover from that early mother-kitten bond.
When It Could Signal a Health Problem
Most of the time, this licking is harmless social behavior. But if one cat is persistently, repeatedly focused on the other cat’s rear end, it could mean the cat being groomed has a medical issue that’s producing unusual scents or discharge.
Anal sac problems are one possibility. When a cat’s anal sacs become impacted, the glands enlarge due to retained secretions, causing pain and discomfort. If the condition progresses to inflammation (anal sacculitis), the area around the anus becomes red, swollen, and painful. In severe cases, an abscess can form, sometimes rupturing and producing bloody or pus-like discharge. A cat with any of these problems may produce stronger or unusual odors that attract another cat’s attention.
Intestinal parasites are another consideration. Tapeworms, for example, shed small segments that look like grains of rice or sesame seeds and can appear around a cat’s anus. These segments can cause irritation, and the affected cat may scoot or seem uncomfortable. If you notice your cat being licked excessively in that area, take a close look for any visible segments, redness, swelling, hair loss, or discharge.
A few signs that suggest something medical rather than social grooming:
- Frequency and intensity. The grooming cat seems fixated, returning to the area repeatedly rather than doing a quick pass.
- Visible changes. Redness, swelling, hair loss, or broken/sparse fur around the groomed cat’s rear.
- Behavioral changes in the groomed cat. Scooting on the floor, excessive self-licking of the area, biting at the base of the tail, or signs of pain when sitting.
- Discharge or odor. Any bloody, pus-like, or unusually strong-smelling discharge from the anal area.
If the groomed cat shows spiky, rough-feeling fur in patches (rather than soft, naturally thin hair), that’s a sign the hair is being actively removed by grooming rather than falling out on its own. Cats experiencing pain or skin irritation in the lower belly, inner thighs, or genital area will sometimes over-groom those spots themselves, which can compound whatever attention they’re getting from a housemate.
What You Can Do
If both cats seem relaxed during and after the grooming, and the behavior happens occasionally rather than obsessively, there’s nothing you need to do. Your cats are just being cats. The groomer is gathering scent information and reinforcing a social bond, and the groomee is accepting it as part of their relationship.
If the behavior is new, has suddenly increased, or you’re noticing any of the physical signs described above, it’s worth checking the groomed cat’s rear end for visible issues. Look for swelling around the anus, rice-like particles (tapeworm segments), redness, or missing fur. Any of these warrant a veterinary visit, as anal sac disease and parasites are both straightforward to treat when caught early. The licking cat, in this scenario, is essentially doing you a favor by flagging that something is off before you might have noticed it yourself.