Why Are Cats' Eyes Reflective At Night?

Do your cat's eyes look demonic at night? Like, even more diabolical and haunted than usual?

Thankfully, it's nothing too sinister behind the strange effect — there's a perfectly scientific explanation why your angelic fur baby's eyes seem to glow in the dark.

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Visual hunters

Cats' bodies have evolved to make them finely tuned hunters. In the wild, they're mainly on the prowl for birds, small rodents and even insects. Cats are obligate carnivores, meaning they must eat meat to survive, so hunting is kind of a big deal for them. Pet owners don't always see this ferocious side of their kitties because indoor cats mainly hunt for hair ties and attention.

The tapetum lucidum

In conditions where there is only a small amount of light available, cats' spooky eyes can help them catch prey like pros. The cat eye has a reflective surface behind their retinas called the tapetum lucidum, which is Latin for "shining tapestry." The tapetum lucidum acts like a mirror, allowing photoreceptors called rods and cones a second opportunity to absorb whatever small amount of light is available. Therefore, the eerie glow we see in is actually light reflecting off the tapetum lucidum, and definitely, probably, not anything demonic.

"Cats' tapetums can reflect up to 45% of the light passing through the eye," Dr. Jessica Kania, a Chicago-based veterinarian, told Cuteness. "Humans, unfortunately, don't have a tapetum lucidum." This is why we get "red eye" in photos, which is actually just blood vessels in our eyes showing up.

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Hunting at dawn and dusk

Cats are crepuscular, meaning they're active around dawn and dusk, which is when their prey is also most active. In these conditions, it really helps to have a shiny mirror in your eyeballs in order to catch as much light as possible.

"Cats' natural circadian rhythm makes them active around dusk and dawn," Kania said. "I think that's why it also makes them incredibly demanding and stubborn during those times — cats are an enigma." Anyone who owns a cat can anecdotally attest to how "active" cats are around dusk and dawn, which seems to be their favorite time for doing zoomies around the house.

Cats aren't the only animals with the tapetum lucidum. There's a long list of other animals that have the reflective surface, including deer, horses, and ferrets.

"The tapetum is differently colored depending on the animal, breed, and age," Kania explained. "In dogs it can be blue, green, yellow, orange, or red. In cats it is usually yellow or green." Even different breeds of cat can reflect different colors in their shiny eyes.

If you're looking to take better pictures of your cat and worried about the tapetum lucidum showing up, the best thing to do is making sure you're taking photos in a well-lit room. Areas with low light will cause the glow to appear more vibrant.

The tapetum lucidum isn't the only feature cats have to make hunting easier. Cats' ears, for example, have the ability to hear high-pitched sounds imperceptible to dogs and humans. Even the cat's most adorable feature—its whiskers—can aid in hunting: they help a cat locate the size and location of an object or animal nearby.

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Cats are clever and cuddly, but they're also fierce predators. Sometimes pet owners forget this, because cats live lives of luxury — that is, they live in our homes for free and have all their meals provided for them. But in the wild, cats are murder machines wrapped in fluff.

Perhaps their haunted, glowing eyes are a stark reminder of that sobering reality: we live among tiny killers with machetes for fingers who've allowed us to be their food dispensers because somewhere deep down, they love us.