Skinks are a diverse group of lizards, recognizable by their typically smooth, fish-like scales and often reduced limbs. Skinks are generally non-vocal, meaning they do not produce complex calls like many birds or mammals. However, certain species can produce subtle sounds, typically restricted to brief hisses or squeaks in reaction to stress or when captured.
The General Rule of Silence
Skinks, like the vast majority of lizard species, are usually quiet because their communication relies on signals other than sound. Lizards primarily use visual cues, such as specific body postures, head-bobbing, and color displays, to convey information about territory, aggression, or courtship. Communication is also heavily reliant on chemical signals, using pheromones deposited in the environment or sensed through the vomeronasal organ to identify mates, rivals, or prey.
The silence of skinks is rooted in their physiology, as they lack the complex laryngeal structures optimized for generating modulated sound. Their basic laryngeal structure is sufficient for breathing but not for complex phonation. This reliance on non-auditory signals is common among diurnal reptiles living in open or semi-open habitats where visual displays are highly effective.
Specific Sound Production Mechanisms
When a skink produces a sound, the mechanism falls into two categories: mechanical noise and physiological defense sounds. Mechanical sounds are incidental byproducts of movement, such as rustling through dry leaf litter or the scraping of scales against a hard surface. These sounds are not intentional forms of communication but simple acoustic consequences of physical activity.
The true defense sounds are physiological, resulting from the forceful expulsion of air. The most common defensive sound is a sharp, brief hiss, generated when the skink contracts its costal muscles to push air rapidly across its glottis, the opening to the windpipe. This mechanism is similar to a snake’s hiss but is lower in volume and shorter in duration. Some species, when severely stressed or physically grasped, may emit a short squeak or huffing sound.
These sounds are not considered true vocalizations because they lack temporal and frequency modulation. They are an unmodulated burst of noise, a simple byproduct of a sudden and forceful respiratory action. The low volume and short-lived nature of these sounds limit their effectiveness to close-range interactions, such as a direct encounter with a potential predator.
Context and Purpose of Skink Sounds
The rare instances of sound production in skinks are almost exclusively tied to negative stimuli. The primary purpose of a skink’s hiss or squeak is defensive behavior, often used as a startle tactic intended to momentarily alarm a predator or a handler. The hiss is frequently accompanied by visual cues, such as a blue-tongue skink flattening its body to appear larger, opening its mouth, and rapidly displaying its large, brightly colored tongue to amplify the threat. These sounds serve the immediate function of encouraging a predator to release or retreat, allowing the skink a chance to escape.