Reptiles frequently extend and retract their tongues, a distinctive behavior. This action, often observed in snakes and many lizards, represents a specialized interaction with their surroundings, setting them apart from many other animals. This unique tongue movement is a hallmark of their sensory biology.
Sensing the World Chemically
The primary reason many reptiles flick their tongues is for chemoreception, a sophisticated form of sensing that combines smell and taste. This process allows them to detect chemical cues from their environment that are not airborne like typical smells. Central to this ability is a specialized sensory organ known as the vomeronasal organ, also called Jacobson’s organ. This organ processes chemical information collected by the tongue, providing detailed insights into the reptile’s surroundings.
The vomeronasal organ is a paired chemoreceptor located in the roof of the mouth in many reptiles, particularly in lizards and snakes. Unlike the main olfactory system, which detects airborne odors, the vomeronasal system detects non-volatile chemical particles. These particles might be present on surfaces or suspended in the air. When the tongue delivers these chemical samples to the vomeronasal organ, specialized sensory cells analyze them, sending signals to the brain for interpretation.
The Tongue’s Role in Detection
Tongue flicking is a precise mechanism for gathering chemical information. A reptile extends its tongue, often rapidly, to collect chemical particles from the air and various surfaces. Once extended, the tongue acts as a sampler, picking up non-volatile molecules that convey environmental data. The tongue is then quickly retracted into the mouth.
Upon retraction, the collected particles are delivered directly to the vomeronasal organ. In snakes and many lizards, this organ has openings in the roof of the mouth, which the tongue touches to transfer samples. The forked tongue, common in many squamate reptiles like snakes and some lizards, enhances this process. Its two tines allow the reptile to sample chemicals from two distinct points simultaneously, enabling “stereo” chemical sensing to determine the signal’s origin direction.
Decoding Chemical Signals
The chemical signals gathered by a reptile’s tongue and processed by its vomeronasal organ provide information about its environment. This allows them to navigate their surroundings and make decisions. Reptiles use these signals to locate prey, often following chemical trails. They can also detect predators, helping them avoid danger.
Chemical communication is important for social interactions, particularly in finding mates. Pheromones, chemical signals released by individuals of the same species, play a role in identifying reproductive status and attracting partners. These chemical cues help reptiles identify their territory and recognize other individuals of their species. For instance, some lizards use chemical signals deposited in feces for scent-marking and recognizing conspecifics.
Diverse Reptilian Tongues
While chemoreception is a primary function for many reptile tongues, especially in snakes and some lizards, their form and use vary widely. Not all reptiles use their tongues primarily for chemical sensing. For example, chameleons possess a specialized tongue used for prey capture. Their long, sticky tongues extend rapidly to snatch insects, adhering through adhesion and suction.
Other reptiles use their tongues for different purposes. Geckos, for instance, often use their broad tongues to clean their eyes. Lacking eyelids, geckos rely on their tongues to keep their eyes clear of debris. This shows the functional diversity of reptilian tongues, with adaptations leading to various specialized uses beyond chemical detection.