Why does my cat have this weird expression?

Have you ever seen your kitty make this face: eyes kind

of spaced out, mouth hanging open but no sound coming out? In a human this expression would look like they just found a very bad odor.

But in a cat it is the opposite. They just smelled something very interesting! This expression is known as a “flehmen response.”

Cats are equipped with a special piece of sensory ‘equipment’ known as the Jacobson’s organ or vomeronasal organ. Located in the roof of the mouth, it contains ducts that lead to the mouth and to the nose. The Jacobson’s organ is used primarily for analyzing pheromones (specialized scent chemicals) from other cats, especially the scents found in urine. These scents are collected in the mouth, and then the cat uses their tongue to flick it up to the vomeronasal organ.

Since the African wildcats (Felis silvestris lybica) which are the ancestors of our domestic cats (Felius catus) are solitary creatures, they evolved a way to find a mate while avoiding unnecessary interactions with other wildcats. Such interactions could lead to dangerous fights over territory. Particularly males needed to sense that a female cat was ‘in heat’ and able to conceive. Domestic cats have retained this ability.

You can tell when the cat is in the process of using their Jacobson’s organ because the facial expression is similar to a grimace; the upper lip will be curled and the mouth will be partially open.

Many other mammals, such as horses, also have vomeronasal organs. Even some snakes!

For more information see: http://www.catbehaviorassociates.com/what-is-the-vomeronasal-organ/