The fascinating world of tongue-flicking
Greetings from the magical world of Scaly Slimy Spectacular! The prominent bifurcated (or forked) tongue of snakes – and even some lizards – is a hallmark of their anatomy. In fact, some people have become so infatuated with the split tongues of snakes, they have surgically modified their own tongues to resemble them. Of course, the million-dollar question: Why do snakes and some lizards possess bifurcated tongues?
The answer to this question has changed a bit over time, as more research has gleaned insight into the physics and anatomy of tongue-flicking. As best as scientists understand it today, snakes and lizards use an organ dedicated for enhanced smelling capabilities called the vomeronasal or Jacobson’s Organ. This organ is located on the roof of the mouth, and particles from the animals’ surroundings can be transferred easily via the tongue. However, a forked tongue increases the number of particles that can be transferred (due to increased surface area) and can also give more detailed information from an otherwise normal tongue.
The anatomy of a forked tongue consists of a single shaft that splits into two equal-length tines. Interestingly, the length of the tines may vary depending on the sex of the organism (e.g., male copperheads have longer tines than their female counterparts). A simple flicking motion collects particles in the air, and the tongue is then retracted back into the mouth where the particles are then transferred to the vomeronasal organ on the roof of the mouth (which may be a more complicated process in its own right, but I digress…). Since each fork delivers particles to its own vomeronasal structure, the organism may be able to determine the direction a smell is coming from – just like people can determine the direction noise is coming from using both of our ears.
The physics of snake tongue-flicking (which may not necessarily hold true for lizards which have similar bifurcated tongues) has only recently been investigated, and the observations have been absolutely fascinating. When you see a snake tongue-flick during your next visit to Zoo Atlanta, try to pay attention to the direction and movement of the shaft compared to that of the tines (which is probably much easier done using the slow-motion feature with a camera phone). You will see that as the shaft of the tongue goes down, the tines will start to point up – and vice versa. That’s because the swift downward motion creates two donuts or vortices of air containing particles from the environment. Perhaps you’ve even seen this phenomenon watching a swimmer do the butterfly, in which circling air bubbles appear underwater during each downstroke on each arm. However, the reason the tines of snake tongues point back up is to increase the amount of contact with each circling vortex of air. It’s a slight yet remarkable evolutionary marvel of snake tongue anatomy and behavior utilizing the physics of motion!
I hope that this has piqued your interest in reptile anatomy and hope to see you soon at Zoo Atlanta checking out some of our tongue-flicking reptiles!
(photo: Noah C.)
Keeper II, Herpetology