What is the Flehman Response in Cats?

The Flehman Response is an interesting phenomenon that’s seen in many species, from mammals to reptiles. The origins of this term are German, meaning "bare teeth" or "look aggressive" but the true purpose of the Flehman Response is nothing short of harmless This silly expression has some fascinating science behind it and may just teach you some feline anatomy you didn't know. So what is the Flehman Response, and why do cats do it? Let’s explore.

The Flehman response, or "flehming" as it’s sometimes called, looks like the face cats make before a sneeze—with upturned lips, somewhat squinty eyes, and the mouth somewhat agape. If the cat's mouth if open wide enough, you may even notice their tongue curled back toward the roof of their mouth.

To understand the purpose of the Flehman response, you’ll need an anatomy lesson on the vomeronasal organ, aka Jacobson’s organ. The vomeronasal organ, is a tiny gland is situated just above the hard palate, in the back of your feline’s nasal septum. It acts like a second nose, except it gives cats more information than just what’s for dinner.

This peculiar organ is a receptor for pheromone-related information, and the Flehmen response ensures that those pheromones make their way up there. You see, when cats perform the Flehman response, they’re pushing air into the vomeronasal organ using their tongue. The tongue thrusts pheromone-laden air into their Jacobson’s organ through tiny ducts on the roof of their mouth. Once the pheromones make it to the vomeronasal organ, it triggers nerve responses in the accessory olfactory bulb and the brain to elicit behavioral responses (like mating) in the feline. 

Unlike smelling, the Flehman’s response is involuntary, so cats have to make a conscious effort to do it. What may look like a silly face is a cat taking in tons of information about the animals around them. Cats can learn about other animals’ sex, mating status,  lineage, and other invaluable information just by doing this little “snarl.”

The Flehman response is a natural behavior, though there are some things you can do to encourage it. Getting your cat a fellow feline pal is sure to spark up the Flehman response, especially if their friend is of the opposite sex. Cats are particularly interested in pheromones of the opposite gender. Using feline calming sprays may also stimulate the Flehman response since they mimic feline pheromones. Cats may also elicit this response to pheromones from other species—some even do it when smelling their owner’s socks!  The main thing you can do to encourage this behavior is to take note of what makes your cat "flehm" and increase the stimulus.

Age and sex can play a part in how often animals exhibit the Flehmen response. For instance, young female horses display this response much more than older females. You may notice your feline presents this response less often as they get older—this is completely normal and not a sign that something is wrong. The Flehman response may be confused with a grimmace or a scowl, but it's not your kitty being moody; they're just investigating their surroundings! If your cat makes this face but seems to be lethargic, or having trouble breathing, see a vet immediately—you could be misinterpreting this face for a medical issue. 

The Flehman response is a common expression in cats, and it means that they’re interpreting biochemical information emitted from other animals. Next time you see your cat making this silly face, know that it’s totally normal. Your kitty is just trying to get a whiff of what’s going on around them! Want more info on other puzzling animal behaviors? Check out our other behavior guides here.