If you've ever tripped over your tabby at night and received the "Why didn't you see me?" glare, you know cats can see much better in darkness than people can. In fact, your cat's minimum light detection threshold is about seven times lower than yours. Yet, both feline and human eyes require light to form images. Cats can't see in the dark, at least not with their eyes. Also, there's a downside to seeing at night.
How Cats See in Dim LightThe tapetum lucidum of a cat's eyes reflects light back toward the retina (or camera). AndreyGV, Getty Images
A cat's eye is built to collect light. The rounded shape of the cornea helps capture and focus light, eye placement on the face allows for a 200° field of view, and cats don't have to blink to lubricate their eyes. However, the two factors giving Fluffy the advantage at night are the tapetum lucidum and composition of light receptors on the retina.
Retinal receptors come in two flavors: rods and cones. Rods respond to changes in light levels (black and white), while cones react to color. About 80 percent of the light receptor cells on a human retina are rods. In contrast, around 96 percent of the light receptors in a cat's eyes are rods. Rods refresh more quickly than cones, too, giving a cat faster vision.
The tapetum lucidum is reflective layer positioned behind the retina of cats, dogs, and most other mammals. Light passing through the retina bounces off the tapetum back toward the receptors. The tapetum commonly gives animal eyes a green or gold reflection in bright light, compared to the red eye effect in humans.
Siamese and some other blue-eyed cats do have a tapetum lucidum, but its cells are abnormal. The eyes of these cats shine red and may reflect more weakly than eyes with normal tapeta. Thus, Siamese cats may not see in the dark as well as other cats.
Seeing Ultraviolet Light (UV or Black Light)Humans can't see black light, but cats can. tzahiV, Getty Images
In a sense, cats can see in the dark. Ultraviolet or black light is invisible to humans, so if a room was lit entirely by UV, it would be completely dark to us. This is because the lens in the human eye blocks UV. Most other mammals, including cats, dogs, and monkeys, have lenses that permit ultraviolet transmission. This "superpower" may be useful to a cat or other predator by making it easier to track fluorescent urine trails or see camouflaged prey.
Fun Fact: Human retinas can perceive ultraviolet light. If the lens is removed and replaced, like for cataract surgery, people can see in UV. After having one of his lenses removed, Monet painted using ultraviolet pigments.
Trading Light for ColorCats see blue and yellow better than red and green. They can't focus as clearly or distantly as humans. masART_STUDIO, Getty Images
All the rods in the feline retina make it sensitive to light, but this means there's less room for cones. Cones are the eye's color receptors. While some scientists believe cats, like humans, have three types of cones, their peak color sensitivity is different from ours. Human color peaks in red, green, and blue. Cats see a less-saturated world, mostly in shades of blue-violet, greenish-yellow, and gray. It's also blurry in the distance (greater than 20 feet), like what a near-sighted person might see. While cats and dogs can detect motion better than you can at night, humans are 10 to 12 times better at tracking motion in bright light. Having a tapetum lucidum helps cats and dogs see at night, but in the daytime it actually reduces visual acuity, overwhelming the retina with light.
Other Ways Cats "See" in the DarkCat whiskers use vibration to map the surroundings. francesco, Getty Images
A cat uses other senses that help it "see" in the dark, sort of like bat echolocation. Cats lack muscles used to change the shape of the eye's lens, so Mittens can't see as clearly close up as you can. She relies on vibrissae (whiskers), which detect slight vibrations to build a three-dimensional map of her surroundings. When a cat's prey (or favorite toy) are within striking range, it may be too close to see clearly. A cat's whiskers pull forward, forming a kind of web to track movement.
Cats also use hearing to map surroundings. At the low frequency range, feline and human hearing is comparable. However, cats can hear higher pitches up to 64 GHz, which is an octave higher than a dog's range. Cats swivel their ears to pinpoint the source of sounds.
Cats also rely on scent to understand their environment. The feline olfactory epithelium (nose) has twice as many receptors as that of a human. Cats also have a vomeronasal organ in the roof of their mouths that helps them smell chemicals.
Ultimately, everything about feline senses support crepuscular (dawn and dusk) hunting. Cats don't see in the dark, but they come pretty close.
- Cats can't see in the dark, but they can detect light 7 times dimmer than humans.
- Cats can see in the ultraviolet range, which appears dark to humans.
- In order to see in dim light, cats have more rods than cones. They sacrifice color vision for improved night vision.
References and Suggested Reading
- Braekevelt CR (1990). "Fine structure of the feline tapetum lucidum". Anat Histol Embryol. 19 (2): 97-105.
- Dykes RW, Dudar JD, Tanji DG, Publicover NG (September 1977). "Somatotopic projections of mystacial vibrissae on cerebral cortex of cats". J. Neurophysiol. 40 (5): 997-1014.
- Guenther, Elke; Zrenner, Eberhart (April 1993). "The Spectral Sensitivity of Dark- and Light-adapted Cat Retinal Ganglion Cells". Journal of Neuroscience. 13 (4): 1543-1550.
- Let the light shine in. Guardian News, 30 May 2002. Retrieved 18 February 2018.
- R. H. Douglas; G. Jeffery (19 February 2014). "The spectral transmission of ocular media suggests ultraviolet sensitivity is widespread among mammals". Royal Society Publishing: Proceedings B.
- Snowdon, Charles T.; Teie, David; Savage, Megan (2015-05-01). "Cats prefer species-appropriate music". Applied Animal Behaviour Science. 166: 106-111.