PH
Cats don't rely only on their noses to investigate smells. They also have a vomeronasal organ, sometimes called Jacobson's organ, that helps detect certain chemical signals.
A cat investigating an interesting scent may briefly hold its mouth partly open in an unusual E×ρréššion called the Flehmen response.
The behavior helps move chemical information toward this specialized sensory system.
© Cornell Feline Health Center