Why Do Cats Leave Their Mouths Open?


If you’ve spent any time observing your cat, you know that she can entertain you for hours. Watching her chase a bug, climb on furniture, or roll on her back relates to natural feline activities that you can also see in wild cats, such as tigers and leopards. If you’ve been very observant you will have noticed another behavior that your cat shares with her undomesticated cousins, flehmen. This unusual name (pronounced flay-men) comes from a German word that describes curling the upper lip.

Do you ever catch your cat with her mouth open?

Cats often keep their mouths hanging open to help them investigate their surroundings. When cats discover an interesting scent, they open their mouths as they try to identify the aroma. The cat wrinkles her nose and her upper lip pulls back, creating a funny face. As your cat considers the scent, she sucks in air and transfers it to a Jacobson’s organ, also known as the vomeronasal sac, which can be found behind the teeth in the roof of a cat’s mouth. This organ processes the scents and sends signals to the brain.

What smells so good?

The scents in question often relate to territoriality, as cats smell urine marks left by other members of the species. They also kick into gear when a female cat in heat leaves scents in an area, but it is not thought to occur in response to another animal. Males are more likely to display flehmen, but mother cats depend on it to keep track of their kittens. The behavior may also be used to distinguish foods or catnip availability.

Other species perform similar acts, including snakes that stick their tongues out to explore their environment and elephants that reach out with their trunks. It is thought that the behavior is enjoyable for animals, and some seem to go into a trance-like state during the process. Herd animals, including cows, horses and donkeys are very demonstrative in their flehmen behaviors, and we can all recall images of horses lifting their heads to the sky as they curl back their lips and suck in air. The next time you see your cat with her mouth hanging open, see if you can identify the scent she is experiencing yourself.

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