Why Do Cats’ Eyes Glow?

Sometimes, seeing the bright glow of an animal’s eyes in the dark can be quite unnerving, but did you know […]

Sometimes, seeing the bright glow of an animal’s eyes in the dark can be quite unnerving, but did you know that this is a special adaptation used by mostly nocturnal (most activity occurring at night) or crepuscular (most activity occurring during dawn and dusk) animals? This phenomenon, known as eyeshine, results in the appearance of glowing eyes, particularly in dimly lit environments. 


The Tapetum Lucidum

The eyes of certain animals appear to glow due to a unique structure called the tapetum lucidum (Latin for “shining layer”), a layer behind their retinas that enhances their night vision. This adaptation allows them to see in low-light conditions more effectively than humans. The tapetum lucidum reflects light that passes through the retina, giving it a second chance to stimulate the photoreceptor cells. This mirror-like membrane is not present in the eyes of humans; we have dark-colored cells behind our retinas, which absorb light rather than reflect it. 

Cat’s Use of Eyeshine

For cats in particular, the tapetum lucidum serves a crucial evolutionary purpose. In the wild, felines are crepuscular hunters, meaning they are most active during dawn and dusk when light levels are low. By having this reflective layer, cats can make the most of available light, giving them a significant advantage when hunting and navigating their surroundings. The ability to see in low light is especially beneficial for stalking prey, avoiding predators, and maintaining awareness during the darker hours. 

Eyeshine in Other Species

The tapetum lucidum is not exclusive to cats, though. There are numerous other animals that also possess this structure. However, the intensity of eyeshine can vary between species and even individual animals. Most of the animals possessing eyeshine are mammals, but it can be seen in some bugs, reptiles, and amphibians as well!

Colors of Eyeshine

A fascinating fact is that the animals with the brightest eyeshine, like the bobcat, tend to have more rods and fewer cones in their retinas. This means that their night vision is great, but most are colorblind. The color of the eyeshine is influenced by the species, the amount of light, and the direction from which the light is hitting the eye. These colors range from red, orange, yellow, green, blue, and white. Cats mostly have either green or yellow eyeshine, but sometimes it does appear almost blue. 

Cats have often been depicted as otherworldly, mystical, mysterious, or magical in myths, folklore, and literature. I think this is in part due to these glowing eyes. Their eyes certainly add to their captivating appearance, but it’s important to remember that these glowing eyes are not a supernatural occurrence, just a natural adaptation!

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