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If a cat detects an odd or unfamiliar scent, it may hold its mouth open for what seems like an unusually long period. This is known as the flehmen response, or 'stinky face.' As kitten rescuer Hannah Shaw mentioned on Instagram, it’s simply a cat’s way of examining a strange scent. This behavior allows the scent to reach the vomeronasal organ located on the roof of the mouth. The vomeronasal organ—also referred to as Jacobson’s organ—is a sensory area within the olfactory systems of mammals, amphibians, and reptiles.
Although the cat’s expression may appear peculiar, it’s simply pulling back its upper lip. The cat uses its mouth, not its nose, to inhale air and direct it toward the vomeronasal organ. Scientists believe the sensory signals traveling through this organ fall somewhere between the senses of smell and taste. While dogs also possess these receptors, cats have around 30 different types compared to the dog's 9. Even larger cats, like lions and tigers, display the flehmen response, as do other creatures like horses and hedgehogs.
A behavior similar to the flehmen response is the 'blep'—when a cat doesn't fully retract its tongue. In this case, the cat is absorbing pheromones from its environment, which are then transferred to the vomeronasal organ. It may appear silly and endearing, like the flehmen response, but cats perform the blep for a reason.
Male cats are more likely to show the flehmen response than females, but female cats use it to keep track of their kittens. As veterinarian Sasha Gibbons told Catster, 'Male cats use the flehmen response in relation to mating. Scents can help indicate compatibility and if the timing is right.' Neutered male cats, however, may still display the flehmen response even without the intention of mating.
Next time your cat pulls that face, take a photo or video and share it on Instagram. See if you can figure out what she’s sniffing.
