Who’s Flehmen Who?

If  you’ve owned cats for a while, you’ve probably noticed a strange behavior that happens once in a while.  Your cat will appear to be sniffing something, then she will open her mouth a little, wrinkling the skin on her nose as she retracts her upper lip and begin to breathe in and out of her mouth.  She’ll hold this posture for a few seconds, then go about her business.  This funny facial expression has been given the almost as funny name of flehmen (pronounced flay-men) – a German word meaning to curl the upper lip. For a video of the behavior see  http://lovemeow.com/2009/10/funny-cat-face-flehmen-response/


Cats aren’t the only animals to do this.  Some other wild felids such as tigers do it, horses, donkeys, cattle and a whole slew of other wild ungulates do it as well.  The horses and cattle are much more dramatic in their flehmen behavior; they curl their upper lip back on itself, open their mouths and lift their heads to the sky.  If you want to see photos of a variety of species demonstrating flehmen,  Click HERE to see pictures.

What causes this behavior and what does it mean, if anything?  Flehmen occurs in species that have vomeronasal organs (VMOs).  These are a pair of small sensory organs that are near, but not a part of the regular olfactory system.  The VMO (formerly known as the Jacobson’s organ – I’m showing off here) is packed with olfactory receptors, but unlike the other nasal olfactory organ, it opens into the roof of the mouth as well as the nasal cavity, and it is connected to different parts of the brain.  It is thought that flehmen helps the animal draw odors into the vomeronasal organ.  While it seems that all animals that flehmen have VMOs, not all animals with VMOs flehmen.  Case in point – dogs.  They have very nice VMOs, thank you, but don’t flehmen. 

The adult males of species that flehmen do it more often than females.  They most often do it when inspecting the urine or ano-genital areas of females.  It is thought to help males determine the reproductive state of the females – in heat, coming into heat, pregnant, lactating and so on.  Females also flehmen in reproductive contexts, but more often when sniffing their young, especially newborns.

Both males and female cats do it at other times as well.  Both will flehmen when they encounter urine from other cats, such as that sprayed on your new drapes, or urine puddles on the floor or in the litter box.  Some cats do it when sniffing catnip, our cat Buffett used to do it when playing with catnip toys.  Cats will sometimes flehmen when encountering new things or new smells.  Perhaps these new or unusual things smell a little like cat reproductive odors.  We don’t know for sure.  Studying chemical communication in cats or other species is difficult for us since our sense of smell is so much poorer than that of most other mammals. 

It does not appear that flehmen is a communicative signal to other animals.  We don’t see a consistent response to the flehmen from others watching it, so it doesn’t seem to cause a change in their behavior.

So there you have it.  You now know almost as much as the scientists about flehmen behavior in cats.  You can add this little bit of knowledge as item 56 in your list of “Weird Things Cats Do That We Don’t Understand.”         

  • Contact Us

    Animal Behavior Associates, Inc.
    7900 W. Layton Ave. #905 Denver, CO 80123