Many lizard species throughout the world display vibrant blue tails, a striking feature. This distinctive coloration is not merely aesthetic; it represents a fascinating evolutionary adaptation. The blue tail serves various purposes, primarily related to survival and defense in their natural habitats.
Lizards Commonly Displaying Blue Tails
Several lizard species are known for their bright blue tails, particularly during their juvenile stages. One prominent example is the American five-lined skink, Plestiodon fasciatus, found widely across the eastern United States and parts of Canada. Young five-lined skinks exhibit a dark body with five distinctive white or yellowish stripes, culminating in a brilliant blue tail. As these skinks mature, the blue coloration of their tails fades, becoming gray or brownish, and their body stripes may also diminish.
The Western skink, Plestiodon skiltonianus, is another species recognized for its blue tail, inhabiting the western United States and British Columbia. Similar to the five-lined skink, Western skinks display broad stripes and a vibrant blue tail when young, which fades with age. Beyond North America, the Christmas Island blue-tailed shining-skink, Cryptoblepharus egeriae, once endemic to Christmas Island, also features a small black body with two yellow stripes and a bright blue tail.
Biological Reasons for Blue Tails
The vivid blue coloration observed in the tails of many lizards is an evolutionary strategy for survival. This bright hue serves as a decoy, drawing the attention of predators away from the lizard’s main body. When a predator targets the conspicuous blue tail, the lizard can detach this expendable body part and escape. This tactic increases the lizard’s chance of survival by diverting an attack from more vulnerable areas like the head or trunk.
The blue color is created by specialized pigment cells called iridophores, which contain guanine crystals that reflect specific wavelengths of light. The intensity and ultraviolet (UV) reflectance of these blue tails can vary among populations. This indicates that the coloration is finely tuned to the visual systems of their primary threats. The bright, contrasting tail also creates a “motion dazzle” effect, making it harder for a predator to accurately judge the lizard’s speed and trajectory during an escape.
Tail Autotomy and Coloration
Many lizards with brightly colored tails possess the ability of caudal autotomy, a self-amputation defense mechanism where they can voluntarily detach their tail when threatened. After detaching, the severed tail continues to wiggle, creating a distraction that allows the lizard to flee to safety. This ability is facilitated by specific fracture planes within the tail’s vertebrae, allowing for a clean break.
When a lizard regenerates a lost tail, the new growth differs in appearance and structure from the original. Regenerated tails are duller in color, often lacking the vibrant blue of the original, and can have a different texture. Structurally, the regrown tail contains a cartilaginous rod instead of the bony vertebrae found in the original tail, along with elongated muscle fibers. The regeneration process demands significant energy from the lizard, which can impact its growth or reproductive efforts temporarily.