Meet the creatures with the most powerful, sensitive, weird, and sophisticated eyes in the animal kingdom, and learn how they compare to human vision.
Which animal has the best eyesight? The question is not as easy as it might seem at first glance. There are many aspects of vision we could consider, including visual acuity or sharpness, range of the light spectrum that can be seen, number of colors that can be discriminated, low light sensitivity, depth perception, field of view, speed of motion detection, ability to quickly focus on both near and far objects, blindspots, and more. There’s a spectacular array of eye designs in the animal kingdom, in part because eyes are thought to have evolved at least 40 times independently. All of this means it isn’t possible to definitively rank animal eyesight from best to worst, but there are certainly some amazing animals that far surpass us in various aspects.
So let’s meet them!
You might have specific questions like:
- Which animal has the sharpest vision?
- Which animal can see with the least amount of light?
- Do any animals have 360-degree vision?
We’ll get to all that, but first, it might be helpful to consider…
The Human Baseline
Although there are some things we don’t have—like good night vision, the ability to see ultraviolet (UV) light, or the ability to see well underwater—humans actually see pretty damn well compared to the broader animal kingdom. Primates (including us) have the best daytime vision among mammals, and humans are perhaps the best among primates. There’s even a case to be made that humans have the best all-around daytime non-peripheral vision of any animal, and some vision scientists do make this claim.
Why primates evolved such excellent vision is an open question, and there have been many theories proposed including that early tree-dwelling primates needed exceptional vision to hunt and grab insects, to judge distances when jumping between tree branches, and even that our evolutionary ancestors developed superior eyesight due to being stalked by camouflaged snakes. However, none of these theories are firmly established.
For visual acuity, we measure normal human vision (20/20) based on the clarity/sharpness that typical well-functioning human eyes see when standing 20 feet away from an eye chart. 20/40 means you need to be 20 feet away to make out what others can see at 40 feet, and 20/15 means your vision is so good that at 20 feet you see fine details that most others need to be 15 feet away to make out. 20/10 is thought to be the maximum acuity of human eyes. Another way to measure visual acuity is in cycles per degree, or how many black and white parallel line pairs can be distinguished within one degree of an animal’s field of view before the lines turn into a gray smudge. This can be estimated for other species based on eye anatomy or using behavioral tests. Humans can see about 60 cycles per degree, better than most animals.
The Animal Champions
Best visual acuity: Birds of prey like eagles, hawks, and falcons soar above their competitors when it comes to seeing the furthest during the daytime, easily beating human visual acuity. Eagles and hawks are thought to have the sharpest vision in the animal kingdom and some species have the equivalent of 20/2.5 eyesight, which means they can make out small details up to eight times further away than humans can, enabling them to spot a meal three kilometers away. They also see more colors than us, including colors in the UV spectrum.
Best night vision: Cats and owls are famous as night vision champs, but are they the best? Not by a long shot. For comparison, we can use lux, a measure of light per square meter. Bright sunlight is well over 10,000 lux, but human eyes can operate with as little as 1 lux. Domestic cats can see in just 0.125 lux, or one-eighth the light we need. Owls can do maybe 10 times better than that. Tarsiers need only 0.001 lux, and dung beetles take it down to 0.001–0.0001 lux. But for the ultimate night vision, a few stand out: The xylocopa tranquebarica species of carpenter bee needs only 0.000063 lux, enabling them to continue flying (a hard task), foraging, and seeing colors on moonless nights. The deep-sea gigantocypris is listed in some reports as the best of any animal at gathering light, though they see at low resolution. But the lowly American cockroach is likely the winner. Their sight has been measured in a different way, so I can’t directly compare them using lux, but they’re able to respond to light received by their eyes at less than one photon per second, making them essentially impossible to beat based on the laws of physics.
Special Mentions
Most complicated eyes: Mantis shrimp have got this one in the bag. They have independently roaming eye stalks, three pupils per eye (giving each eye independent depth perception), and they can see ultraviolet, far-red, and polarized light. They use 12–16 different types of photoreceptor cells to see color, which compares to our three (for red, green, and blue) and is more than any other animal (although the bluebottle butterfly is up there with 15 types). You might think this means they can see dramatically more colors (the Oatmeal’s popular comic about them hypothesized their vision is a “thermonuclear bomb of light and beauty”), but in fact, they seem to do rather poorly in tests for distinguishing color. That’s only one of the reasons National Geographic describes their way of seeing as “absurdly over-engineered.”
360° field of view: Woodcocks, chameleons, dragonflies, and (depending on the position of their head) jumping spiders can pull this off. However, this vision isn’t perfect. E.g., less than 10° of a woodcock’s vision is binocular (seen by both eyes), which compares to humans’ up to 190° horizontal field of view with 120°–140° being binocular. Dragonflies’ fancy eyesight also comes at a cost: nearly 80% of their brains are dedicated to vision.
There’s also the California purple sea urchin and the box jellyfish, which both have photoreceptors all over their bodies, essentially letting them see all around them (though not without blindspots).
Largest eyes: The colossal squid is the winner for any living animal. Their eyes can reach up to an eye-popping 30 centimeters in diameter, significantly larger than a regulation soccer ball (22 cm) and five times larger than blue whale eyes. Why they have such gigantic eyes is still unknown, but it might help with detecting the faint glow of sperm whales (their only predator) as they disturb nearby light-producing organisms.
Bonus: Cyclopses: All species within the Cyclops genus of copepods have one eye. They’re the only animals like that if you exclude birth defects and microorganisms with eyespots. Fun fact: The one-eyed character Plankton (see image) from SpongeBob SquarePants is a copepod.
Other Super Senses
What about animals with the best senses of smell and hearing? Check out the next articles in this series:
[…] Although we lack some abilities, such as good night vision, the ability to see ultraviolet (UV) light, and the ability to see well underwater, humans see quite well compared to the rest of the animal kingdom. Primates, including humans, have the best daytime vision of any mammal, and humans may be the best of all primates. There’s even a case to be made that humans have the best overall daytime non-peripheral vision of any animal, and some vision scientists agree. (Source: Steven Levithan) […]