Few things in nature are as recognizable as a snake flicking its tongue. Out it comes, wiggling in the air, and then it's gone again. Many people assume the snake is tasting something, or maybe trying to look scary. The real reason is more clever than either guess.
A snake uses its tongue to smell. The forked tongue picks up tiny scent particles from the air, the ground, or even the water. When the tongue goes back in, it delivers those particles to a special sense organ in the roof of the mouth, called the vomeronasal organ or Jacobson's organ, which analyzes them.
A Nose in the Roof of the Mouth
Snakes rely heavily on their sense of smell to track prey. Each flick of the tongue is like taking a sample. The snake collects chemical traces, pulls the tongue back in, and touches it to the opening of the organ, which then reads the information.
Scientists describe the result as a combined taste-smell analysis that gives the snake a detailed picture of its surroundings. That steady stream of scent clues helps a snake find its next meal and steer clear of danger, even when it can't see what it's tracking.
Some snakes even do this underwater. In aquatic species such as the anaconda, the tongue works efficiently beneath the surface.
Why the Tongue Is Forked
The fork isn't just for show. Because the two tips sample slightly different spots, the snake gets directional information about a smell. If the scent is stronger on one side, that's a clue about where prey, or a predator, might be.
It works a bit like having two ears instead of one. Our brains compare sounds arriving at each ear to tell where a noise is coming from. A snake can compare scents from each side of its tongue to figure out which way to go.
Proof From the Lab
Researchers have shown just how much snakes depend on this organ. Garter snakes need it to sense the scent of prey in the air. In experiments, garter snakes whose vomeronasal nerves were cut responded only to non-prey odors, as if they could no longer recognize a meal.
Garter snakes also use the organ to communicate with each other through chemical signals called pheromones. In a sense, the tongue helps them read messages left by other snakes.
You Might Have Seen Your Cat Do This
Snakes aren't the only ones with this extra scent organ. It's found in all snakes and lizards and in many mammals, including cats, dogs, cattle, pigs, and primates.
Some mammals have their own funny-looking way of using it. Cats and horses sometimes lift their heads, wrinkle their noses, curl back their lips, and briefly stop breathing after sniffing something interesting. It's called the flehmen response, and it helps steer scent chemicals toward the organ. If you've ever seen a cat make a strange open-mouthed face after sniffing a shoe, now you know why.
The organ was first discovered by Frederik Ruysch sometime before 1732, and later by Ludwig Jacobson in 1813, which is where the name Jacobson's organ comes from.
So the next time you see a snake flicking its tongue, you can picture what's really going on. It isn't licking the air or making a threat. It's taking a long, careful sniff, one quick flick at a time.
