Chameleons are Tongue Fu Masters. What makes a chameleon tongue so lethal is the complex bone structure which the tongue is wrapped around. This skeletal structure is held between the lower jawbone; like an arrow nestled in a crossbow. The structure is called the Hypobranchial Apparatus, and is comprised of two main parts – a ‘U’ shaped bone called the Hyoid Bone, and a matchstick-sized bone called the Hyoid Gleam which is catapulted outwards, shooting the tongue tissue towards its victim.
Around the Hyoid Gleam, tightly wound coils of collagen tissue are sandwiched between the bone and the tongue; this is called the Entoglossal Process. This is like a spring and creates potential elastic force. Release this force, and the tongue ejects outwards along Hyoid Bone. Held within the Entoglossal is the same kind of force or pressure created when your arm is holding back the string of a bow & arrow – when you let go of the string, the force is released to propel the arrow. In this case, the Entoglossal tissue is released to propel the tip of the tongue towards its target.
When a chameleon is hungry, it triangulates on its prey with both eyes, bringing into focus the approximate distance between itself and its next meal. Instinct dictates the force required to reach the destination – up to 3x body length away – and judges the force to use as to not fall short or overreach. The center of the pad at the tip of the tongue is tense and firm, similar to a pencil eraser. Around this pad there is soft mushy tissue. When the force of the tongue hits a solid target, the firm pad stops and the remaining kinetic energy forces the soft tissue to keep moving forward, wrapping around the insect. The variation between a tense center and soft surrounding tissue creates a mild suction.
At the moment the tongue is fired, muscles are used to project the sticky pad at the tip of the tongue at speeds reaching 1/16th of a second. First, the U-shaped Hyoid Bone is pushed upwards and outwards, pushing out the Hyoid Gleam. The energy held in the wound up collagen tissue is released to push the sticky tip forward. The collagen tissue and accelerator muscles surrounding the Hyoid Gleam are similar to a toy lightsaber – the different sized cones are held within the hilt in your hand, and when swung outwards with force, all the cones extend to full length. Aside from toy lightsabers, this method of telescoping muscle tissue only exists in nature in chameleon tongues and is completely unique to them.
While a chameleon tongue can’t harm you, the most damage that can be done to the chameleon itself is after impact. The struggle for life begins for the victim, and flailing limbs can cause damage to the mouth or eyes. Many insects have spikes which can harm sensitive areas on the face of your chameleon. To prevent this harm, most chameleons will aim for the head of an insect to immobilize it, and the chameleon will close its eyes as they retract the tongue back into the mouth.
The muscles used to reel the tongue in are different than the ones used to shoot it out. The retraction process takes longer than the acceleration because the extended tongue no longer has its potential elastic force – the tongue goes from a tight spring to a floppy slinky. This is where some mishaps can occur.
Sometimes the tongue will shoot out, but if the shot hits nothing but air, the tongue may hang fully extended off the tip of the Hyoid Gleam like a wet sock. In this situation, the Entoglossal muscles will quickly activate and coil the tongue back into the Hyoid Horn and another attempt will be made.
If your chameleon misses its target frequently, or the tongue dangles for prolonged periods of time, this may indicate a nutritional deficiency or dehydration. Calcium is important for muscle function and mobility, and hydration is important for proper function.
It is important to know that there is always the possibility that the suction made upon impact will catch more than just an insect. This is why it is frowned upon to keep bark or soil in a chameleon habitat. Ingestion of these materials can cause blockages in the digestive system called impaction, and this is lethal to chameleons.
See our guide to supplementation and hydration to learn more about how these factors affect chameleon tongues.