Meet the creatures with the most powerful, sensitive, weird, and sophisticated eyes in the animal kingdom.
Eyes are thought to have evolved at least 40 times independently, and there’s a spectacular array of eye designs in the animal kingdom. The many aspects of vision (including visual acuity, light wavelengths that can be detected, low light sensitivity, ability to detect motion/objects, depth perception, color discrimination, and field of view) mean it isn’t possible to definitively rank animals’ eyesight, but there are certainly some amazing animals that far surpass us on various aspects.
So let’s meet them! You might have specific questions like: What animal has the best eyesight day and night? Which animal has the widest range of vision? Do any animals have 360° vision? We’ll get to all that, but first, it might be helpful to consider…
The Human Standard
Although there are some things we don’t have — like night vision, ability to see ultraviolet (UV) light, ability to see well underwater, and super-wide field of view — humans actually see pretty damn well compared to the broader animal kingdom. In fact, we probably have the best daytime non-peripheral vision of all mammals. Not bad, humans!
For visual acuity, we measure normal human vision (20/20) based on the clarity/sharpness you should 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 other people need to be 15 feet away to make out. 20/10 is thought to be the maximum acuity of human eyes.
The Animal Champions
Best visual acuity: Eagles, hawks, and falcons can see the furthest during the daytime, easily beating human visual acuity. Although there isn’t a lot of precise data distinguishing visual acuity between particular species, eagles and hawks are thought to have the sharpest vision in the animal kingdom and some species have the equivalent of 20/2 eyesight, which means they can see up to 10 times as far as humans can. 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 not-usually-admired 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.
Most complicated eyes: Mantis shrimp have got this one in the bag. They have independently roaming eyes, 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 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, which compares to humans’ 180° field of view with 140° being binocular. Dragonflies’ fancy eyesight also comes at a cost: nearly 80% of their brains are dedicated to vision.
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 the blue whale. Why they have such gigantic eyes is a mystery, but it might have something to do with detecting sperm whales, their only predator.
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 from SpongeBob SquarePants is a copepod.
What about animals with the best hearing and smell? Check out my additional articles in this series: