
A cat giving out the Flehmen response.
The flehmen response, from German flehmen, to bare the upper teeth, and Upper Saxon German flemmen, to look spiteful, also called the flehmen position, flehmen reaction, flehmen grimace, flehming, or flehmening, is a behavior in which an animal curls back its upper lip exposing its front teeth, inhales with the nostrils usually closed, and then often holds this position for several seconds. It may be performed over a sight or substance of particular interest to the animal, or may be performed with the neck stretched and the head held high in the air.
Flehmen is performed by a wide range of mammals, including ungulates and felids. The behavior facilitates the transfer of pheromones and other scents into the vomeronasal organ (VNO, or Jacobson's organ) located above the roof of the mouth via a duct which exits just behind the front teeth of the animal.
Description[]
This response is characterized by the animal curling back its top lip exposing the front teeth and gums, then inhaling and holding the posture for several seconds. The behavior may be performed over particular locations, in which case the animal may also lick the site of interest, or may perform the flehmen with the neck stretched and head held high in the air for a more general gustatory or taste-related investigation. The flehmen response often gives the appearance that the animal is looking spiteful, grimacing, smirking, disgusted, or laughing.