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. Etymology The word originates from the German verb flehmen, to bare the upper teeth. It comes from the Upper Saxon German flemmen, "to look spiteful". The word was introduced in 1930 by Karl Max...