EYES MIGHT NOT be able to speak, but they have plenty to say. Many animals use complex visual systems to help them survive in particular habitats. Sight is often a first line of defense against predators—or a crucial sense for catching prey. To dwell in Earth’s darkest locations or travel high through the sky, creatures have evolved special and bizarre ways to perceive their worlds.
Spookfish: Mirrored orbs
It’s gloomy year-round for the spookfish, a spiked carnivore that swims in the dark depths of the ocean. Sunlight rarely penetrates more than a few hundred feet below the surface, so this critter uses mirrors instead as well as lenses to see—the only known vertebrate with this feature. The disks, made of guanine crystals, can focus light emitted by bioluminescent plankton and other glowing marine life. Weirder still, the funky fish’s eyes are split into two connected parts: one section gazes up while the other looks down. That way, it can spy food above and below it, as well as lurking predators.
Golden eagle: Cones galore
In North America, Europe, and Asia, golden eagles soar on 7-foot wingspans while searching for small prey like rabbits, which they can spot more than a mile away. The birds can see from great distances thanks to an extreme density of visual cells known as rods and cones in their retinas. Rods generally register the overall shape of an object, whereas cones detect color and detail. In general, the density of rods and cones in a raptor’s eye is five times greater than in a human’s.
Giant squid: Titanic eyes
The largest eyes in the animal kingdom, at up to 10 inches in diameter, belong to adult giant squids. And it makes sense: The…
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