If you ever looked closely at a snake’s tongue, you would notice that it is not quite the same as most of the animals’. It is actually forked in the middle. The tongue of the serpent has intrigued humans for thousands of years; still, its function remained unknown until recently. This kind of forked tongue is found in all snake species as well as in some reptile species. So, why is it that the tongues of snakes are forked? And also, why is it that they like to keep flicking them?
Snakes are deaf and unable to hear airborne sounds. Instead, they rely on their visual capabilities to observe the world. Besides, being very light, they can detect extremely small vibrations within the ground or air. They use this to map their surroundings very accurately. The answer to why their tongues are forked is that snakes need forked tongues to “smell” their environment.
In fact, snakes need forked tongues in order to smell in stereo. What does this mean, exactly? It’s the same as listening to something in stereo. If you listen to some music while using only one side of the headphones, it seems like the whole orchestra has been squeezed into a single, tiny speaker.
If you use both sides of your headphones, you will notice that the music feels much more like a 3-dimensional experience. Similarly, it is easier to guess the depth of something in real life with both eyes open rather than with only one eye open.
What’s happening here is that, both in the case of your ears and your eyes, your brain uses two separate perspectives to combine them into a much more detailed and three-dimensional input. Only because you have distinct eyes and two ears are you able to visualize and hear everything in stereo.
When a snake flicks its tongue through the air, it can pick up several, odor-causing particles. The two parts of its forked tongue stretch as far apart as they can. Whatever chemicals each of the tines can catch become attached to the tongue. It transfers these “smell particles” to a special sensory organ called the vomeronasal. Also known as the Jacobson’s organ, it is found at the back of the nose and is accessible through two small grooves on the roof of the snake’s mouth.
In order to “smell” the chemicals attached to its tongue, the reptile has to lick the base of the grooves. This allows the odor-causing particles to reach into the grooves and access the sensory organ.
The main advantage of the split tongue of snakes is thought to be the 3-dimensional perception of a smell. As each of the tips pick up smells from different spots in the air, then by comparing the two samples, snakes can get to know the direction of the smell’s source. Just like we use our ears to comprehend sound waves, snakes do the same thing with different smells.
The direction where the smell is stronger must be the one where the smell is coming from. As long as both tips are on the odor trail, the snake keeps going straight. But when the tongue diverts from the trail, the snake veers in another direction in order to put itself back on track. If neither of them is on the trail, the snake stops and waves its head back and forth to pick up the odor again
This vomeronasal perception is useful for three main purposes. Firstly, snakes use it for reproduction purposes by detecting pheromones released by potential mates. Secondly, by identifying each kind of smell, they can get to know the location of their food. Thirdly, snakes learn to associate different smells with either a threat or some landmark that helps them avoid predators and navigate more easily.
In case you were thinking about it, yes, we humans also have vomeronasal organs. However, we don’t use them anymore. These organs are classified as one of those traits that were useful to our ancestors, but not to us. So, at some point in history, our bodies stopped using the vomeronasal organs due to disuse. Other examples of such organs include your wisdom teeth, moving your ears using your ear muscles, and the appendix.