Whatever you call it, if you have a pet cat at home (especially if it’s a male) you’ve likely seen this face before. It goes by many variations of the same name: Flehmen Response, Flehmen Position, Flehmen Reaction, or simply Flehming. Flehmen (pronounced: FLAY-men) Responses are used by a wide variety of hoofstock (ungulates) and many cats (felids). Males and females, adults and babies, all exhibit this silly facial expression.
The silly look on the animal’s face helps to activate an organ that allows him or her to sense chemicals in the air; specifically pheromones. Pheromones are a chemical signal that passes useful social information to another animal of the same specie. The organ used is called the Vomeronasal organ (also called the Jacobson’s Organ). This organ is located in the nasal cavity of many animals, including fetal humans. It is the organ used by snakes and water turtles as their primary sense of smell, but in most other animals it is used in more of a secondary or social fashion. More animals use a Vomeronasal Organ to detect pheromones than those that display the Flehmen Response, like lemurs, salamanders, lizards, dogs and pigs.
The lip curl or grimace directs the inhaled air toward the Vomeronasal Organ, allowing it to pick up the chemicals in the air and let the animal know important information about what they’re smelling. Information like whether there’s a female nearby who’s looking to mate or simply to get a more complete understanding of a new smell they’re being introduced to. Lightning, the donkey, often exhibits Flehmen Response to new smells and Chummix, the Boer goat, does it after smelling his urine (it’s a male goat thing…).