Cats are generally graceful and delicate creatures, so it can really come as a surprise when they suddenly lean into another cat and catch the scent of their butt. Why do cats do this?

This may seem strange, especially considering how humans communicate, but it's actually an important part of feline behavior. that's why.

Butt sniffing is a very natural, instinctive and basic form of cat-to-cat communication. Oddly enough, this is how cats greet and get to know each other, while also sniffing their chests and necks. Even cats that know each other well will sniff butts to "see what's new" and to strengthen their bond and communication.

A cat’s butt is the olfactory equivalent of a cat’s “Hello, how are you?” similar to how humans use a handshake when meeting and being introduced to someone. Cats use their strong sense of smell to communicate with each other and to detect signals from chemicals in anal gland oil.

What will you know if you smell it?

To understand what smell can tell cats, it’s important to understand how cats are different. There are four main differences between how cats communicate and how humans communicate:

The first difference between cats and humans is cats’ amazing sense of smell. They reportedly have about 40 times more olfactory cells in their nasal passages than we do. With such a strong sense of smell, cats rely on this sensory information far more than humans do. It is so intense that a cat entering the room can sense whether another cat that entered the room previously was happy, nervous, scared, or in heat. While it's difficult for humans to fully understand how this works, "smell" can also somehow tell cats whether an encounter is likely to be friendly or unfriendly.

Cats have prominent and active scent glands on their heads, necks, paws, chests and the base of their tails, as well as active anal glands. These apocrine sweat glands, located on either side of a cat's rectum, produce a strong-smelling secretion designed to send chemical signals to other animals about the cat's identity. These signals include the cat's gender, what the cat is eating, and even some clues about the cat's emotional state.

The third difference worth noting is the presence of Jacobson's organ (also called the vomeronasal organ). This is a small piece of olfactory nerve tissue filled with extrasensory receptors that sense odors traveling through the air. Also found in many animals, including dogs, snakes, and even elephants, it transmits information to the brain from locations inside the trunk and mouth. You may notice a cat activating their Jacobson organ when making faces, which is called the "Fryman response." Cats often turn up their noses and curl their lips to optimize their ability to "smell" this way.

The last big difference is that withUnlike humans, cats will reintroduce themselves frequently, sometimes several times a day or even an hour. Any change or irritation usually leads to butt sucking. Some people believe that "sniffing" can actually relieve tension and stress by helping a person feel more comfortable around another cat. When a cat comes in from outside or returns from the vet, two cats living in the same house may smell each other's scent to confirm information about the cat's status, including diet, stress, availability for mating, and mood.

What should you do when sniffing your butt

Behaviorists advise that because butt sniffing is a normal part of cat behavior, it's best not to disturb a cat if it seems friendly. Interrupting this behavior is equivalent to preventing a friend from shaking hands with the person they are meeting: it can annoy or upset the friend and may make the introduction awkward. In fact, the lack of this butt-sniffing communication between cats can cause stress between cats.

That being said, some cats are more aggressive "sniffers" than others, and not every cat that meets will actually like the other. If the sniffing becomes intense and you notice any other signs of aggression, it may be appropriate to pull your cat away from the other cat.