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What is that glow?
Throughout history, people have offered various explanations for the mysterious glow in cats’ eyes. The ancient Egyptians believed cats captured sunlight at dusk to safeguard it until dawn. In Celtic tradition, a cat’s eyes were thought to be a portal to another world, while poet W.B. Yeats described our feline friends as “the nearest kin to the moon.” But what’s really behind this eerie glow?
What causes cat eyes to glow in the dark?
Unlike humans, cats have a special layer at the back of their eyes, called the tapetum lucidum (2), that acts as a tiny mirror.
When light enters a cat’s eye, some of it hits photoreceptors in the retina (1). These are special cells that send signals to the brain to create an image. Some light passes through the retina (1) where it is bounced back by the tapetum lucidum (2), increasing the light available to the photoreceptors. Now, some of that reflected light misses the photoreceptors in the retina (1) again and shines back out, making the cat’s eyes look like they’re glowing – a phenomenon called eyeshine.
Are there any benefits to eyes glowing in the dark?
Absolutely! Cats are crepuscular animals, which means they’re most active at dusk and dawn. To hunt prey in low-light conditions, our feline friends need excellent eyesight—and that’s where the tapetum lucidum (2) comes in. While cats cannot see in total darkness, the reflective layer greatly improves their vision in dim light, making them incredibly skilled hunters.
Are there other animals whose eyes glow in the dark?
Many animals’ eyes glow in the dark, with the color of the glow varying across species. Deer and elk have white eyeshine, while the reflection in moose’s and rabbits’ eyes looks red. Bears and mountain lions’ eyes typically exhibit a yellow-to-red glow, horses’ eyes shine blue, and tigers’ eyes usually appear green in the dark.
