If you have cats you have probably seen them walking up to something, parting their lips, and take a few deep sips of air. Your cat has a rudimentary nose of sorts on the roof of her mouth that biologists call the vomeronasal or Jacobson’s organ, a relic of reptilian days that your pet uses to sense who has been around and has left their calling card. It looks like a pair of grooves, connected to the nasal cavity. Cats spend a lot of time rubbing their chins against things: a set of sebaceous glands here leaves a scent that we humans cannot (thankfully) smell well (if at all). The odor is particular to each cat. When a cat strokes you with her chin, she is sending a message to all the other cats around that she owns you. You are her territory.


Horses, cattle and sheep also use the vomeronasal organ. Biologists call the sampling of scent through this organ the Flehmen. When you see your cat walking around like a gourmet sampling the treats at a wine and cheese party, you can rest assured that the cat is using this hybrid sense of taste and smell to see who has been around and, perhaps, what kind of mood they were in when they came by.