Why do cat eyes glow in the dark?

Imagine driving into a dark alley. It’s pitch dark, all except for the car headlights, and… a pair of two golden eyes staring straight at you. To your fright, the eyes move closer to reveal… a little cat! You breathe a sigh of relief and you start to wonder, “How and why does that happen?”

A cat’s eyes tend to shine when light is reflected on them. This glow is created when light from a torch, car headlights, or a camera flash is shone on them. The eyes reflect the minimal light that falls on them. Let’s dive into this phenomena a little deeper.

Behind the light

Eyes — whether of a human or of a cat — are built with a retina, which is a thin layer at the back of your eye and creates signals your brain can understand. But what do cats have that humans don’t? A special extra layer called the tapetum lucidum, which reflects it back through the retina. This, in turn, helps the retina capture the light a second time. The glow you see in cats’ eyes at night is actually light bouncing off the tapetum lucidum.

Cat eyes in the dark
| Photo Credit:
UNSPLASH

Glow in action

Cats are most active during the dawn and the dusk hours of the day, and hence their eyes are built for low-light vision and hunting. With the tapetum lucidum, cats are able to see in places which are too dim for the human eye. This gives them a major advantage when hunting small animals at night.

However, this comes at a cost. The tapetum lucidum is not so sharp in broad daylight as it is in the nighttime. This is one reason cats often prefer shady spots or dim environments.

The reflective glow also comes in handy for people, especially for researchers and photographers to spot animals at night.

Cat eyes in the dark
| Photo Credit:
UNSPLASH

Colours and creepers

The glow can have various shades, ranging from yellow to blue, and even green. There are many factors that affect this, including:

• the angle of the light

• the distance from the cat

• the structure of the tapetum lucidum

Kittens tend to have a bluish tint to their eyes, while older cats have a yellow, or yellowish-green light emitting from their eyes.

Cat eyes in the dark
| Photo Credit:
UNSPLASH

An animalistic instinct

It’s not just cats. Many nocturnal animals — such as dogs, foxes, crocodiles, deer, tigers, and crocodiles — have this reflective layer.

The eerie glow of a cat’s eyes may look mysterious, but it is actually a clever adaptation that helps them see and hunt in near darkness. They hence make the most of the night, turning it to their hunting ground.