Color perception allows animals to distinguish objects and habitats, find food, and communicate using visual signals. The range of colors that an animal can detect depends on the types of photoreceptor cells it has in its eyes.
Humans can see light wavelengths ranging from about 400 to 700 nanometers, which includes the visible spectrum of red, orange, yellow, green, blue, and violet. The three types of cones cells in the human retina allow us to perceive millions of different colors through a combination of signals from the cones tuned to short, medium, and long wavelengths of light.
Many other animals have different sets of photoreceptor cells that give them unique color vision abilities compared to humans. Some animals have a wider range or shifted range of color vision, others have fewer types of photoreceptors and see a more limited range of colors, while some animals are limited to seeing only shades of grey.
Tetrachromatic vision in some birds, fish, reptiles, amphibians, and insects
Some species have four types of cone cells, allowing them to see more shades of color than trichromatic humans. Having an additional, fourth cone type expands the range of color vision, especially in the ultraviolet spectrum.
Examples of tetrachromatic animals include:
- Birds like zebra finches, pigeons, and chickens
- Fish including goldfish, zebrafish, and trout
- Reptiles such as turtles and lizards
- Amphibians like frogs and toads
- Insects like bees and butterflies
With their ultraviolet-sensitive cones, many birds likely see a rainbow spectrum of colors that humans can barely imagine. Brightly colored fruits, flowers, feathers, eggshells, and skin patches probably stand out vividly for birds against green foliage, which reflects UV light strongly.
Butterflies have photoreceptors tuned for ultraviolet, blue, green, and red light, allowing them to see colors on flowers invisible to humans. This helps them find nectar guides on petals leading to the source of the sugary reward.
Research on honeybees shows they use their ability to see in the UV spectrum to differentiate between flower species and help in communications within the hive.
Dichromatic vision in many mammals
Unlike humans, most mammals are dichromatic – they have only two types of functional cone cells. This is the case for animals like:
- Dogs
- Cats
- Cattle
- Deer
- Horses
- Ferrets
- Mice
With two types of cones tuned to blue and green wavelengths of light, dichromatic mammals can distinguish blue from yellow and green from red, but have trouble differentiating red from green.
So while dichromatic animals can still see color, they have a less rich color experience than humans or tetrachromatic animals. Their world appears mostly in muted yellows, blues, grays, and shades of purple.
Monochromatic vision
Some animal species lack cone cells entirely, meaning they can only see in shades of grey. Animals limited to monochromatic vision include:
- Many marine mammals like whales, dolphins, seals, and sea lions
- Nocturnal mammals such as hedgehogs and bats
- Cephalopod mollusks including octopuses, squid, and cuttlefish
Marine mammals living in deep or muddy waters rely more on their excellent underwater hearing and echolocation abilities to hunt and navigate. As for nocturnal mammals, rod cells providing low light vision are more useful than color discrimination in nearly pitch-black settings.
Unique color vision abilities
Beyond variations in cone cells and color ranges, some animals have additional specializations that provide enhanced color vision capabilities.
Mantis shrimp
Mantis shrimp have 12-16 types of photoreceptor cells, allowing them to see wide spectrum of colors. Some species also have photoreceptors tuned for circularly polarized light, which enhances their ability to distinguish transparent prey.
Reindeer
Reindeer can see light in the ultraviolet range, allowing them to spot food and predators against a snowy arctic backdrop. UV light causes white fur and snow to produce a bluish hue.
Bees
Bees have photoreceptors sensitive to polarized light from the sky. They use this ability for navigation, visually detecting the location of the sun even on cloudy days by the light polarization patterns.
Snakes
Pit vipers, pythons, and boas have heat-sensitive pit organs on their faces that allow them to detect infrared radiation. This lets them accurately strike and capture prey, even in the dark.
How animals use color vision
Color perception provides many advantages for animals in nature. Some key examples include:
- Food detection – Color vision helps animals distinguish ripe fruit and edible plants.
- Predator avoidance – Animals can spot brightly colored toxic organisms or use camouflage to hide from predators.
- Mate selection – Colorful displays play an important role in attracting mates for breeding.
- Communication – Bright colors convey visual signals between members of a species related to mating, territory, mood, etc.
- Navigation – Using cues from the color and polarization of skylight assists with orientation and migration.
Even without full color vision, many animals have adapted unique ways to distinguish important aspects of their environments using the visual abilities they do possess.
Conclusion
While humans enjoy trichromatic color vision spanning the full visible spectrum, many animals see the world with very different eyes. Some creatures can even detect colors and wavelengths beyond what humans perceive. Ultraviolet sensitivity is especially common, as this enhances visibility against natural backgrounds. Other animals have fewer types of photoreceptors, limiting them to muted versions of the world we see. But thanks to their specialized visual systems adapted for the habitats they inhabit, animals are remarkably skilled at using the unique colors they do see to survive and thrive in nature.