Some snakes exhibit a captivating glow when exposed to a black light. This intriguing phenomenon is known as biofluorescence, a natural process where certain organisms absorb light of one color and then re-emit it as a different color. Unlike organisms that generate their own light, these snakes possess special properties in their skin that interact with specific wavelengths. This interaction makes hidden patterns and colors visible, revealing an unseen aspect of their natural world.
Biofluorescence in Snakes
Biofluorescence occurs when an organism absorbs higher-energy light, such as ultraviolet (UV) light, and then re-emits it at a lower energy, resulting in a visible light spectrum. This process involves specialized pigments or proteins within the snake’s skin that act as fluorophores. These compounds absorb the invisible UV radiation and release it as visible light, often appearing as green, orange, or red hues. The specific colors and patterns observed vary depending on the snake species and its unique skin composition.
Researchers utilizing black lights have increasingly observed biofluorescence in snakes. Studies have identified tail biofluorescence in several pit viper species, including Trimeresurus hageni, where glowing colors range from white to various shades of blue and green. This fluorescence appears in structures like scales and rattles in both wild and captive snakes. Beyond external tissues, UV fluorescence has also been detected in snake bones, emitting blue or green light. The Green Cat Snake (Boiga cyanea) is another species found to exhibit biofluorescence.
Understanding Black Light
A “black light” is a specialized lamp designed to emit primarily long-wave ultraviolet-A (UV-A) radiation, which is invisible to the human eye, while producing very little visible light. The slight purplish glow often seen is residual visible light escaping its filter.
When UV-A light strikes fluorescent materials, they absorb the UV energy and re-emit it as visible light, causing them to glow. While UV-A light is generally considered the safest type of ultraviolet radiation, certain precautions are advisable. Prolonged or direct exposure to UV light, particularly staring directly into the beam, should be avoided to prevent potential eye and skin irritation. Wearing protective eyewear is recommended for extended use.
Why Snakes Biofluoresce
The precise reasons behind biofluorescence in snakes are still under scientific investigation, with several theories proposed. One hypothesis suggests it plays a role in communication, such as species recognition or mating signals. This is supported by the fact that some snake prey, like certain frogs and lizards, also use biofluorescence for communication and can perceive UV light.
Another theory posits that biofluorescence could serve as camouflage or a mechanism for predator avoidance. Many arboreal (tree-dwelling) and nocturnal snakes exhibit UV coloration, which might help them blend into environments rich in UV-reflective elements like leaves and lichens. This could offer protection during daylight hours when these snakes are resting and more vulnerable to predators, such as birds, which are known to see in the UV spectrum. For some pit vipers, tail biofluorescence may function in caudal luring, a hunting technique where they wiggle their tails to attract UV-sensitive prey.
Biofluorescence Versus Bioluminescence
It is important to distinguish biofluorescence from bioluminescence, as they are often confused. Biofluorescence involves the absorption of light from an external source, like a black light, and its re-emission at a different, visible wavelength. The organism does not produce the light itself; it merely transforms the absorbed energy. If the external light source is removed, the biofluorescent glow ceases.
In contrast, bioluminescence is the process by which living organisms generate their own light through a chemical reaction within their bodies. This reaction typically involves luciferin and luciferase, producing “cold light” with minimal heat. Examples include fireflies, which use light flashes for communication, and many deep-sea creatures, such as anglerfish, that produce light to attract prey or mates. Unlike these organisms, snakes do not produce their own light; their glow relies entirely on an external light source.