If you ever notice your cat sneering ormaking a “stinky face,” that’s the flehmen response. Also called the flehmenreaction or flehmen grimace, the flehmen response is a behavioral response seenin cats (and other animals such as goats, tigers, and horses) that helps themprocess interesting smells, such as pheromones—chemical compounds secreted tohelp relay messages to other members of their species regarding territory,breeding, and identification.

Here’s everything to know about your cat’s“stinky face” and what it means.

What Is the Flehmen Response?

The flehmen response is a behavioralresponse to certain stimuli (usually odors) that allows an animal to betteraccess the information carried through smell. It’s a voluntary response,meaning the animal deliberately exhibits the behavior (as opposed toinvoluntary responses, such as salivating in response to food or pupilsdilating when anxious orstressed).

When a cat is enacting the flehmenresponse, they will typically hold their mouth open. This allows air to passthrough their vomeronasal organ (also called the VNO or Jacobson’s organ).

The VNO is an accessory olfactory (meaningsense of smell) organ at the base of the nasal cavity. It’s used to processpheromones and hormones secreted by other animals, usually of the same species.By coming in direct contact with these scent molecules, the VNO can thenprocess them as a sensation that has been described as a combination of tasteand smell.

Most animals, including cats, that exhibitthe flehmen response have an opening on the roof of their mouth, just behindtheir front teeth, that connects to a duct that transfers smell directly to theVNO.

It’s not just house cats who use theflehmen response. The behavior has also been observed in wild cats such aslions and tigers, along with other animals including horses, goats, and sheep.

What Does the Flehmen Response Look Like?

In cats, the flehmen response typicallylooks like your kitty is grimacing because of something stinky. The cat willtypically curl their upper lip to expose their front teeth, hold their mouthopen, and inhale. Sometimes, they will extend their neck or hold their headhigh in the air.

This pose is held for a short amount oftime before the cat returns to anormal position; this pose can resemble panting, grimacing, or sneering.

Why Do Cats Open Their Mouth When TheySmell?

In domestic cats, the flehmen response isused to process messages carried by interesting scents. In most cases, this ispheromones from other cats.

Although the flehmen response is mostcommonly used by male cats to assess afemale’s readiness to mate by sniffing her urine, any catcan use the flehmen response as a reaction to a scent they find worthy offurther investigation. Cats can display the flehmen response when they smell:

·       Urine

·       Dirty laundry

·       Anal gland secretions

·       Facial pheromones from other kitties

·       Any other odor that they find intriguing or new!

So while it might look like your cat isreacting to a bad smell, a cat’s flehmen response doesn’t mean your kittysmells something they think is gross! (So don’t get offended if your cat curlstheir lip after sniffing you.)