Why Do Cat Eyes Glow in the Dark?

Why Do Cat Eyes Glow in the Dark?

[INTRO ♪] It can be terrifying to wake up in the middle
of the night to a pair of glowing eyes staring at you from the darkness, only to realize that it’s just your cat. … Or is it? Lots of animals, including alligators, fruit
bats, and dogs, all have a shiny structure in their eyes that gives them better night vision, which
also causes this creepy glow. The layer of tissue at the back of your eyes
is called the retina, and it’s made up of special light-sensitive cells. Light that hits those cells gets turned into
an electrical signal that’s sent along the optic nerve, which sits behind the retina. That signal travels all the way to the brain. And light that misses those cells isn’t
turned into a signal, so your brain can’t detect it. Many species across the animal kingdom have
this same basic eye structure, from reptiles to birds to other mammals like cats. One way animals have evolved to see better
is to have more of those light-sensitive cells in each eye. Humans, for example, have over ninety-five
million of them per retina. But a lot of animals—especially nocturnal
animals whose eyes have to work well at night— have another way of detecting more light. They have a structure called the tapetum lucidum,
which is Latin for “bright tapestry.” It’s a layer of tissue that sits behind
the retina and acts like a mirror. The tapetum lucidum reflects light that gets
through the retina back at those light-sensitive cells, giving them another chance to detect it. But some of the reflected light flies back
out the animals’ pupils, which is what makes it seem like their eyes are glowing. The color of that glow, also called eyeshine,
depends on what the tapetum lucidum is made of. And different critters have different highly
ordered molecules or fibers that create a reflective surface. Some fish eyes use guanine—one of the chemical
building blocks in DNA—and have white eyeshine. Sheep have collagen, which also provides structure
to muscles and skin in lots of animals, which leads to a blue or green glow. And cats use riboflavin and zinc, among other
molecules. And the amount of zinc does a lot to determine
how yellow or green or even blue their eyeshine is. So your kitty’s eyes aren’t actually like
little flashlights; they’re just reflecting some of the ambient light in your room. But if they start glowing red and shooting
laser beams, you should probably run. Thanks for asking, and thanks to all of our
patrons on Patreon who keep these answers coming. If you’d like to submit questions to be
answered, you can go to patreon.com/scishow. And don’t forget to go to youtube.com/scishow
and subscribe!

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  1. It's said that the inventor of the cats eyes on the road did so because he saw a cat walking towards whilst driving along and his eyes shone. What they don't tell you is that at the same time a man was driving in the other direction, he invented the pencil sharpener.

  2. Cows and Deer have this layer in their eye too. You learn this driving in rural Texas [among other places]. Some spiders have this >:]

  3. Its sad what human race has come to be. Instead of using google on to why cat eyes glow, they need a YT video to spoon feed them. Disgusting.

  4. I already knew that the light is reflected from behind of their eyes since I saw some documemtary about tigers few years ago,but I never knew why the light is different in example cats and dogs
    thank you for this video!

  5. Michael just gets better looking as he ages. Great speaker, delivers information well, intelligent, and handsome? grrrr…..

  6. Can you make a video where you compare the mechanism of learning in mammal brain/humans (on a neurophysiological level, for example LTP, hebbian theory etc.) and artificial intelligence (how learning is achieved in anorganic materials/computers).
    I'd really like to know if there are similarities (like the concept of trial and error) and of course to know more about the fundamental differences (design-wise)…

  7. This channel is great. Is my first time here and i ljust love it!! thank you for the very good and helpfull information

  8. Are you serious? My cats eyes shines red. No laser, I watched this video to learn something serious not for comedy.

  9. I almost find it hard to believe animals' eyes actually appear to glow, since I've never seen it in person, and with photos my brain insists that it's something about the camera.

  10. Really enjoyed the learning presented in this video but was also somewhat distracted by how cute this guy is, lol

  11. Because in 1967 a cat ate a lightbulb and, kind of like how everyone has mitochondrial DNA like a specific person but much faster because cats have shorter lifespans, now all cats have glowing eyes.

  12. my hetero-chromatic dog's eye shines are different colors for each eye respectively; blue eye – red shine brown eye – green shine……EXPLAIN!!!

  13. my eyes glow red and gold like cat eyes at night i told my eye doctor he said its the first he heard of a human to have eyes that are like a cats

  14. I'm a little creeped out because a lot of cats that I see have eyes that glow in the dark red 🙊🙊but still love them lmao😻😻

  15. I know the red reflection of the eye is a threat for a fact when a strangers cat went inside my home fighting my cat i splashed water on the cat and repeatedly my cat was winning the fight and i know that from here on me and my cat have to watch our back.. thanks for the eye opening video. Thanks

  16. Cats with Siamese stock have eyes that glow red. This is how I discovered why the calico kitten we adopted would not shut up. (Smeezers are yappy creatures.)

  17. My answer is that the cat got that ability as a reward for saving a very important person's life. It's called dua. This person who got saved made dua for all the cats and it got accepted. I might seem like a weird person, but if you look more deeply into where this story comes from, you will see that it makes sense.

  18. Cats. Change. At night.
    They are nice and cute animals, but doesn't anyone really notice that cats change of behaviour in the night?

  19. Here in my profile image is my albino Tom. His eyes glow red. Is that normal for an albino? By the way, thank you for the video 🙂

  20. 1:49 that's what my cat had been doing for past few days i was wandering why it acted so weird it's good to know the real problem

  21. A Cats eyes shine because they reflect light, even in the darkest night, they usually same stray light or the headlights of a car. House cats are the not the only cats that reflect light, Jaguars, lions, tigers, leopards and all other cats that shine at night !

  22. Very interesting!
    One of my cats have heterocromia, she has one greenish brown eye and one ice blue eye. The eyeshines are even different – the brown one shines green and the blue one shines red. I can only guess that the blue eye has no pigments in it so that's why the eyeshine is red? Like albino animals?

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