Why do cats open their mouths after smelling something?

Cats often open their mouths after smelling something because of a behavior known as the flehmen response. It’s a behavior seen in many mammals, where they open their mouths and curl back their lips after detecting an interesting smell. Cats rely heavily on chemical communication, and the flehmen sniff, which looks like a grimace or sneer, helps draw scent molecules into the Jacobson’s organ, or vomeronasal organ, located on the roof of the mouth. This specialized organ detects pheromones and other chemical signals.

The flehmen response lifts a flap behind the incisors, directing scents into the Jacobson’s organ. Chemical cues from the scent carry detailed information about the cat’s surroundings, including messages related to mating and territorial boundaries. Through this sensory response—best described as a cross between taste and smell—cats can gather more nuanced information than they would through their regular olfactory senses alone. This is vital for cats to understand social cues and environmental changes, which can influence their behavior and interactions with other animals.