Can cats see in the dark?
I don’t know about you, but I can barely make it to the bathroom in the middle of the night without tripping over the dog and stubbing my toe on the corner of the dresser. The cats, meanwhile, are doing a tightrope walk on the second-story banister in complete blackness, like circus acrobats.
It begs the question, can cats see in the dark?
While it sure seems like cats have some kind of midnight superpower, cats cannot see in true, complete darkness any better than any other living thing with eyes. But what cats can do is make use of the barest sliver of light, which most certainly exists in most of our modern homes.
The dark of night actually isn’t all that dark
What often feels like complete darkness to us, really isn’t. The numbers on your alarm clock emit a soft glow. The halo from the nightlight in the hall seeps beneath your bedroom door. Moonlight trickles in through the edges of your window shades. There’s probably more light in your “dark” house at night than you think.
Outdoors there’s light too: from street lamps, car headlights, and all-night gas stations.
Cats’ eyes were designed to capture that measly bit of light and use it to help them navigate in the dark. We’ll explain how they do it, but first, let’s explain how eyes – both human and cat – work.
How do cat and human eyes see?
Most objects in the world don’t shine on their own. The only reason we can see everyday things – like cereal boxes and trees – is because light (natural light from the sun, or artificial light from lightbulbs) bounces off of them.
Light that hits the cereal box or tree bounces off in every direction continuously. But some of the bounced-off light hits the cornea of your eye or your cat’s eye. Corneas are clear in both species, like windows.
The pupil, which sits behind the cornea, decides how much of that light it’s going to let in. If there is barely any light, the pupil will open as wide as possible to let it all in. But if there is a crazy amount of light, like on a sunny day at the beach, the pupil will let only a small amount light squeeze by, so the eye isn’t overwhelmed.
The light that slips in past the pupil continues moving to the back of the eye. There’s a layer of cells there, called the retina. The retina is made up of nerve cells, called photoreceptors. “Photoreceptor” literally means “light receiver.”
There are two kinds of photoreceptors in cats and people: rods and cones. They each have different jobs, which we’ll discuss in a moment, but both turn the light they receive into electrical signals. These signals travel through the optic nerve to the brain which converts those signals into the “pictures” we see.[1]
It’s almost too amazing to be believed.
Cats’ eyes were designed for hunting
The first eyes in the animal kingdom were probably just simple “eyespots” that could only distinguish between light and dark. Over time, the eyes of different species evolved from eyespots to do the specific jobs their owners needed them to do.
Some fish, for example, have pupils that are split in half, allowing them to see above the water and below the water simultaneously. This allows them to watch for both predators and prey at the same time.[2]
Birds, we believe, can use their eyes to see magnetic fields, a trick that could be the magic behind their ability to migrate, finding their way home from thousands of miles away.
Cats’ eyes also evolved, but to suit their specific hunting lifestyle.
Cats’ eyes are designed for ambush hunting
Lions stalk their prey. Wolves hunt in groups. Cheetahs use speed and agility to catch their dinners. Our housecats are ambush hunters, which means that they hide first and then leap out to catch prey.[3]
Cats' eyes evolved to make them better ambush hunters, which in turn, makes them better able to see at night.
Cats’ pupils are the right shape for ambush hunting
Have you ever noticed that cats’ pupils – the black part in the center of the colored part of the eye – is shaped like a vertical, narrow ellipse, compared to human pupils, which are round?
According to vision scientist and professor of optometry Martin Banks, animals have differently shaped pupils for a reason.
Prey animals have horizontal pupils
Banks analyzed 214 land animals and compared the shapes of their pupils. He noticed that prey animals, like sheep, have eyes on the sides of their heads with horizontal pupils.[4]
Horizontal pupils (and eyes on the sides of the head) allow prey animals to get a wide panoramic view of the ground. They can see what’s coming up behind them, and also see what’s coming up ahead, in case they have to suddenly run away.[5]
Ambush hunters have vertical pupils
Animals that are ambush hunters, like cats, have vertical, slit-shaped pupils and eyes on the front of their heads.
Using computer models, they discovered that this combination gives animals better depth perception. Ambush hunters need to be able to accurately judge distance to allow them to successfully pounce on prey.
Slit-shaped pupils also give animals more control over how much light gets into their eyes, and allows them to do well in both very dim and very bright conditions. While human pupils expand 15 times from most constricted to most dilated, cats pupils expand 135 times! [6]
Cats’ eyes help them hunt at dawn and dusk
Cats are crepuscular, which means they do their best work at dawn and dusk.
Some people think that cats are nocturnal, especially since they seem to get busy right when their humans are winding down to go to sleep. You can read about cats who yowl at night in this post.
But cats evolved to be crepuscular because being out and about at those “not-quite day/not-quite night” times is an advantage. Cats hunt when it’s still light enough for them to see what they’re doing, but hopefully too dark to become somebody else’s supper.
Cats have big corneas
In addition to dynamic, slit-shaped, vertical pupils, which can adjust to very dim conditions, cats have giant corneas. A cat’s cornea is about 50% larger than a human’s.
If corneas are the windows of the eye, having larger “windows” lets more light in, and helps cats see better in the dark.[7]
Cats have more rods
The retina, as we mentioned above, is the part of the eye that captures light that’s bounced off objects in the world and sends the information to the brain.
There are two types of photoreceptors in the retina: rods and cones.
Cones are for seeing fine detail and for color perception. Humans have lots of cones, which allow us to detect colors in all their richness, and to see things very clearly.[8]
Rods are responsible for peripheral and night vision. Rods work at very low levels of light. Cats have lots of rods – six to eight times the number that we have – which gives them excellent night vision.
So, cats can’t see the kind of detail that we can see, or the rich color, but all those rods give them an amazing ability to see in the dark. Cats need only about one-sixth of the amount of light that humans need to be able to see.[9]
Cats have a tapetum lucidum
Cats have a special mirror behind their retinas which helps them see in low light.
You’ve probably seen this mirror if you’ve ever seen your cat’s eyes glow in the dark.
The tapetum lucidum is made from 15 different kinds of cells and it is very reflective. It gives the rods a second chance to capture light.
If a tiny bit of light comes into a human eye, but fails to hit a rod, that light is “lost.” It’s why I stumble over my dog in my dark bedroom.
But if a tiny bit of light comes into a cat’s eye and fails to hit a rod, that light will travel to the tapetum lucidum. The light bounces off the shiny tapetum right back to the rods again, giving them a second chance to “see” the light.
The only downside of the tapetum is that it can scatter light, making things appear blurrier in the daytime.
(Cat also use their whiskers to navigate in the dark. Read more about whiskers, in "Why do cats have whiskers?")
Do cats see in color?
Some people think that cats only see in black and white, but this isn’t true.[10]
Cats have fewer cones – the color-perceiving cells – than humans, because cats’ retinas are jam-packed with rods.
So, they can definitely perceive color, but we assume that the colors that they can see look dull. We believe that cats see violet and blue quite well, and some cats may also see green. Reds probably appear grayish to all cats.[11]
Artist Nickolay Lamm created some fascinating photographic renderings of how cats might see the world, compared to how we see the world. He consulted with three veterinary ophthalmologists to be sure he was on the right track. I love this project. You can view it here:
Nickolay Lamm’s, “What do cats see?”
Why don’t cats watch TV?
Most cats don’t watch TV because TV images appear to flicker for them.
Cones are responsible for dealing with flickering. They’re supposed to see the first image, recover, and then see the next image. When the flashing happens too fast, the cones can’t keep up and “fuse,” or make a series of images appear as a single image.
Our cones fuse at 45 Hz. TV screens flicker at 50 or 60 Hz (which is faster). So, humans don’t see the flickering of TV screens, even though it’s happening.
Cats’ cones don’t fuse until 70 to 80 Hz. So, they see a bunch of flashing images on our computer screens and televisions. I wouldn’t watch that either, if I were a cat.
Cats also perceive flickering in fluorescent lights. (This makes me wonder about the lighting in my vet's office).[12]
(You may also be interested in this post, "Why does my cat stare at me?")
Are cats nearsighted or farsighted?
Cats are near-sighted, as ambush hunters should be. A cat needs to be able to see the rat lurking three feet away in order to catch it. They don’t need to be able to see the rabbit nibbling on grass 200 yards away.
Cats don’t have very clear vision compared to humans. We describe average human vision as 20/20. Cats have vision that is closer to 20/100 or 20/200. That means that if we can see an object clearly when we are 100 feet away or 200 feet away from it, a cat would have to be standing only 20 feet away to see that same object clearly.[13]
The reason cats have a harder time focusing than we do is because we have the ability to change the curve of the lenses in our eyes. We have special muscles that flatten and round our lenses to allow us to focus on objects at varying distances.
Cats can’t change the shape of their lenses, but they can pull their lenses back toward their retinas to see objects that are far away, and forward for things that are close up. It works, but it’s not as effective as the system as we have.[14]
But cats don't care. They're happy to bounce off the walls chasing a fly around the house in complete darkness while we're trying to sleep.
I think they're just showing off.
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Dawn LaFontaine is a lifelong animal lover who always seems to have a little pet hair in her keyboard. Her blog, Kitty Contemplations, helps cat guardians better understand and care for the special beings they share their lives and homes with. Her cat-products business, Cat in the Box, sells beautiful, well-made, and award-winning products that she designed to meet the biological needs of cats.
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FOOTNOTES
[1] “How the Eyes Work.” National Eye Institute, U.S. Department of Health and Human Services, https://www.nei.nih.gov/learn-about-eye-health/healthy-vision/how-eyes-work.
[2] Starr, Michelle. “The Weirdest Eyes in the Animal Kingdom See a World We Can't Imagine.” ScienceAlert, https://www.sciencealert.com/the-weirdest-eyes-in-the-animal-kingdom-see-a-world-we-can-t-imagine.
[3] Ellis Last Modified Date: June 13, Jessica. “What Is an Ambush Predator?” All Things Nature, 13 June 2022, https://www.allthingsnature.org/what-is-an-ambush-predator.htm.
[4] Yang, Sarah. “Pupil Shape Linked to Animals' Place in Ecological Web.” Berkeley News, 12 Aug. 2015, https://news.berkeley.edu/2015/08/07/pupil-shape-and-ecological-niche/.
[5] ibid.
[6] ibid.
[7] “Can Cats See in the Dark? Feline Night Vision Facts: Hill's Pet.” Hill's Pet Nutrition, https://www.hillspet.com/cat-care/behavior-appearance/can-cats-see-in-the-dark.
[8] Spector, Dina. “How Cats See the World Compared to Humans.” Business Insider, Business Insider, 10 Mar. 2018, https://www.businessinsider.com/pictures-of-how-cats-see-the-world-2013-10.
[9] ibid.
[10] Ghose, Tia. “Feline Vision: How Cats See the World.” LiveScience, Purch, 16 Oct. 2013, https://www.livescience.com/40459-what-do-cats-see.html.
[11] Lee Pickett, VMD. “Ask the Vet: Cats See Better than People in Dim Light, but Humans See More Colors.” Arkansas Online, 17 Jan. 2022, https://www.nwaonline.com/news/2022/jan/17/ask-the-vet-human-eyes-beat-cats-eyes-for-color/.
[12] “Vision in the Animal Kingdom - WSAVA2008.” VIN, https://www.vin.com/apputil/content/defaultadv1.aspx?id=3866640&pid=11268&print=1.
[13] Spector, Dina.
[14] “Vision in the Animal Kingdom - WSAVA2008.” VIN.