The flehmen response, draws air into an additional chemoreceptor organ, the vomeronasal, or Jacobson’s organ. This organ’s function is to detect pheromones and it is situated above the roof of the mouth (between the palate and the nasal cavity) and is connected to the environment via the nasopalatine canal, which opens behind the upper front teeth (Case, 2003). Air is drawn into the organ during the flehmen response, which can be recognised by the cat opening its mouth slightly and parting its lips to draw them away from the upper teeth to allow scent molecules to enter the canal. The mouth is usually held open in this position for a few seconds during which the lower teeth may be visible.
The video below illustrates a cat that is performing the flehmen response after washing his own anogenital region. During the flehmen response the cat's nose or tongue may make physical contact with the odour's source (Bradshaw & Cameron-Beaumont, 2000) and the cat often licks its nose afterwards (Bateson & Turner, 2000)
The video below demonstrates a female cat exhibiting flehmen after grooming another cat.
The following video shows a male cat exhibiting flehmen after investigating the environment.