Why do cats eyes glow in the dark?

Glowing cat eyes have conjured thoughts of the supernatural for thousands of years, but why do cats eyes glow in the dark? While it might be fun to joke that your cat has X-ray vision, there are some actual scientific reasons behind that glow in cat eyes.

How and Why Do Cats Eyes Glow In The Dark?

A cat's glowing eyes are caused by incoming light reflecting off what's called the tapetum lucidum — Latin for "shining layer" — explains Cat Health. The tapetum is a layer of reflective cells; light bounces off it and reflects back to the cat's retina. This creates the appearance of a glow. ScienceDirect reports that this glow can appear in colors including blue, green or yellow.

Survival Skills

But glowing cat eyes don't just look cool, they serve a clear purpose. The tapetum increases retinal illumination in low lighting, and in combination with the rods in their eyes, allows cats to detect changes in light and motion. These are skills that aid them in hunting - another reason as to why do cats eyes glow in the dark.

Cats are crepuscular animals, meaning they do most of their hunting during twilight. This is when glowing cat eyes come in handy; they function like tiny flashlights, helping navigate through the shadows and distinguish between prey and predator. Your cat might be your favourite cuddle partner but, like their big cat cousins in the wild, they're also a hunter.

Cat Eyes vs. Human Eyes

Cat eyes have better night vision than humans and this is due to the structure, including the tapetum. Yet cats can't make out sharp lines and angles. Everything looks a bit fuzzy to them.

Cats' eyes are also very efficient. According to AdelaideVet “they can see normally with as little as 15% of light that humans would need. Also, their pupils’ function much as the aperture for a camera does, dilating significantly when they need to take in extra light. Cats in particular have exceptionally large pupils for their body size and outstanding night-time vision.”

Another awesome advantage cats have over humans is that they can use their muscles to control how much light enters their eyes. Cat’s turn their pupils into slits in order to absorb less light, when they detect too much. This muscle control also allows them to dilate their pupils on command, which broadens their field of vision and helps them find their way. (You may also notice dilated pupils when your cat's about to pounce, so watch out.)

Don't get frightened the next time you see your cat's eyes aglow — they're just trying to get a better look at you!

Contributor Bio

Christine O'Brien

Christine Brovelli-O'Brien, Ph.D., is a professional member of the Cat Writers' Association (CWA), a STEAM educator, and a devoted pet parent. Her work also has appeared in Fit Pregnancy, What to Expect When You're Expecting Word of Mom, and Care.com. Find and follow her on Instagram and Twitter @brovelliobrien