Cat Sneering: What Is the Flehmen Response?

by Cheryl Lock

If you own a cat, you’re probably well-versed in the number of baffling behaviors they might exhibit on a regular basis, but if you’ve ever seen her make a certain facial expression that looks like a grimace or sneer, you might have also wondered about her health.

Fortunately, it’s more than likely that the facial expression your cat is making is totally ordinary. This reaction, called the Flehmen response, is common in many animals including cats, goats, tigers and horses.

“Several times a week I get a call or question from a client about ‘this weird thing my cat is doing,’” says Dr. Mark Waldrop. “They describe their cat as sneering, or open-mouth breathing, and hovering very intently over an area. This is a totally normal response called a Flehmen response.”

Why Do Cats Display the Flehman Response?

Pam Johnson-Bennett, a certified cat behavior consultant and best-selling author, notices this behavior in cats fairly frequently, and she says the reason is because no matter how hard she tries, she often carries the scent of other cats around with her.

“When a cat displays the Flehman response, she’s basically analyzing a particular scent,” she says. “It’s used primarily for analyzing pheromones from other cats, especially the ones found in urine, but a cat will use it for other interesting scents that require more thorough investigation, too.”

Waldrop says that the most common time he’s seen a cat display the Flehman response in day-to-day life is when one animal in the house has expressed their anal glands.

“Anal gland secretions are rich in pheromones, and the Flehman response allows them to better investigate who it came from,” he says. “I have also seen [the response] in cats investigating where another cat has sprayed urine marking a location or when they smell our dirty laundry that’s left on the floor, specifically socks and underwear.”

It’s also a common response to see when your cat is investigating a new environment, particularly one where other animals have been.

“I see this daily as I return from work,” Waldrop says. “My cats have to investigate all the smells I’ve picked up during my day.”

Signs of the Flehman Response in Cats

To call the look of the response a “sneer” or “grimace” is a good start.

“When a cat displays a Flehman response, it typically looks like a grimace because the upper lip will be curled,” says Johnson-Bennett. “Some cats hold their mouths open more than others, so it can even look as if the cat is panting.”

In terms of the physical response that takes place, a lot of it has to do with their tongue.

“When a cat comes across an interesting scent, it’s collected in the mouth where the tongue is used to flick it up to a specialized organ known as the vomeronasal organ or the Jacobson’s organ,” says Johnson-Bennett. “The Flehman response is basically a combination of smelling and tasting a scent for in-depth investigation. When the cat opens her mouth in a grimace and curls her upper lip, he’s providing maximum exposure for the scent to travel through the vomeronasal organ.”

In general, scent is an extremely important sense to cats, and they have far more scent receptors than humans do. As such, it makes sense that they would come equipped with a specialized organ to take their scent diagnosis to the next level.

While both male and female cats have a vomeronasal organ, males tend to engage it more in order to determine sexual availability of females in the area based on urine scent analysis. So, the next time you notice your cat making a similar face, take stock of her surroundings.

“Even though the vomeronasal organ is primarily used by intact males to determine if there’s a mating opportunity, any cat may display the response in reaction to an interesting scent,” says Johnson-Bennett. “Many of us may unknowingly bring in scents on our shoes or clothing that pique a cat’s interest.”