Some animals smell in a way that may just leave you open-mouthed
If you have a cat, you may have noticed it opening its mouth after sniffing something. Despite the face they pull, cats aren’t shocked by these smells; they’re taking in extra information about them.
Cats – along with big cats, snakes, lizards, lemurs, lorises, elephants, painted turtles and ungulates (like giraffes, cows and horses) – have a specialised sensory organ called the vomeronasal organ (VNO), or Jacobson’s organ. This organ is made up of two fluid-filled sacs and is mostly used to detect pheromones (chemicals used in communication between members of a species). Snakes stick out their tongues to sense their environment, while elephants use the ‘finger’ at the end of their trunks to transfer smells of interest to the VNO in their mouth. There’s a lot of debate about whether humans have the organ, but if we do it’s unlikely that it works.
A cat’s Jacobson’s organ is located behind its teeth on the roof on its mouth, and it contributes to a sense of smell 14 times better than ours. It’s connected to the cat’s nasal cavity and, by opening their mouths, cats can draw the smell into it. This action is called a ‘flehmen reaction’, and is used in response to strong smells and smells from other cats, like urine territory marks and the scent of a female in heat. Female cats also use it to keep track of kittens, and it might play a role in finding and assessing food.
Here’s a pet cat demonstrating the flehmen response: