Observing lizards with their mouths open can appear unusual, but this seemingly simple action serves multiple essential functions for these reptiles. Understanding why lizards open their mouths reveals insights into their survival strategies and interactions with the environment.
To Regulate Body Temperature
Lizards are ectothermic, relying on external sources to regulate their body temperature. When basking, they absorb warmth to reach an optimal temperature for bodily functions. To prevent overheating, they need a way to release excess heat.
Opening their mouths, a behavior known as “gaping,” allows lizards to release this excess heat. This process is similar to how mammals pant, increasing airflow over moist mouth tissues for evaporative cooling. Gaping is a common thermoregulatory behavior, particularly noticeable after intense heat absorption. It is a cooling mechanism and generally not a sign of aggression.
For Communication and Display
Opening the mouth also serves as a distinct form of visual communication among lizards. This behavior is often part of threat displays, where a lizard opens its mouth wide to appear larger and more intimidating to predators or rivals. Revealing bright colors inside the mouth, such as the blue tongue of a blue-tongued skink, further enhances this warning signal.
Lizards also use mouth-opening in territorial displays to assert dominance or defend their space. This can be accompanied by other body language, such as puffing up the body or head bobbing, to amplify the message. Some species incorporate mouth-opening into courtship rituals, with males displaying to females. The context and accompanying body language differentiate these displays from thermoregulatory gaping.
To Sense Their Surroundings
Many lizards flick their tongues out to collect scent particles from the air and ground. These particles are then transferred to a specialized chemosensory organ called the vomeronasal organ, also known as Jacobson’s organ, located on the roof of their mouth. This organ allows them to “smell” or “taste” their environment in a detailed way.
This chemical sensing system is crucial for a lizard’s survival, providing a chemical map of its surroundings. Lizards use this information to locate prey, identify potential mates through pheromones, and detect predators or other dangers. The forked tongue found in many species helps with directional scent detection, allowing the lizard to determine the source of a smell.
Other Common Behaviors
Lizards may also open their mouths for other reasons. When severely stressed or overheated, some lizards might pant more rapidly with an open mouth to increase evaporative cooling from moist membranes. This rapid breathing can be a sign of distress if persistent and accompanied by other symptoms.
Lizards can also yawn, stretching their jaws. While the exact reasons for yawning are not fully understood, it may serve to realign jaw bones after a meal, stretch muscles, or potentially indicate stress. Opening the mouth is also involved in basic actions such as eating and drinking, though these are typically brief and context-specific.