Flehmen response

The flehmen response (/ˈfleɪmən/), (from German flehmen, to bare the upper teeth, and Upper Saxon German flemmen, to look spiteful), (also called the flehmen position, flehmen reaction, 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 site 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 response in a tapirFlehmen response in an elkFlehmen response in a goatFlehmen response in a zebra The flehmen response (/ˈfleɪmən/), (from German flehmen, to bare the upper teeth, and Upper Saxon German flemmen, to look spiteful), (also called the flehmen position, flehmen reaction, 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 site 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. 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 by Karl Max Schneider, director of the Leipzig zoo and an authority on big cats in captivity. The flehmen response was first described by Frederik Ruysch and described later by Ludwig Jacobson in 1813. 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 or laughing. The flehmen response draws air into the VNO or Jacobson's organ, an auxiliary olfactory sense organ that is found in many animals. This organ plays a role in the perception of certain scents and pheromones. The vomeronasal organ is named for its closeness to the vomer and nasal bones, and is particularly well developed in animals such as cats and horses. The VNO is found at the base of the nasal cavity. It is encompassed inside a bony or cartilaginous capsule which opens into the base of the nasal cavity. Animals that exhibit flehmen have a papilla located behind the incisors and ducts which connect the oral cavity to the VNO, with horses being an exception. Horses exhibit flehmen but do not have an incisive duct communication between the nasal and oral cavity because they do not breathe through their mouths; instead, the VNOs connect to the nasal passages by the nasopalatine duct. The chemical cue obtained by an animal exhibiting the flehmen response is the presence of a non-volatile organic compound. In contrast to volatile organic compounds (VOCs), non-volatile organic compounds are those carbon compounds that do not participate in atmospheric photochemical reactions or evaporate under normal atmospheric conditions. The VNO detects non-VOCs, which must have direct contact with the odor source. Sources of non-VOCs relevant to the flehmen response include pheromones and hormones excreted from the genital regions or urine of animals.