Many animals can see a wider range of colors than humans. This is due to differences in the photoreceptor cells found in animal retinas. Photoreceptor cells detect light and transmit signals to the brain, allowing animals to see. There are two main types of photoreceptor cells: rods and cones. Rods allow animals to see in low light conditions, while cones allow for color vision.
How Animal Vision Works
The retina contains millions of photoreceptor cells. In humans, there are approximately 120 million rod cells and 6 million cone cells. Rods contain a pigment called rhodopsin which absorbs light and triggers neural signals to the brain. Cones contain pigments called opsins which are sensitive to different wavelengths of light. There are three types of cones in human eyes which detect short (blue), medium (green), and long (red) wavelengths of light. It is the combination of signals from these three cone types that allows humans to perceive a wide range of colors.
Other animals often have more types of photoreceptor cells, allowing them to see more colors. For example, mantis shrimp have 12-16 different photoreceptor types compared to humans’ 3. Some birds, reptiles, and insects can also see ultraviolet (UV) light thanks to cone cells sensitive to shorter wavelengths than humans can perceive. Additionally, some animals have more total photoreceptor cells than humans – a falcon, for example, has approximately 1 million cones compared to our 6 million.
Animal Spectrums of Color Vision
Different animals see different spectrums of light. Humans are trichromats, meaning we have three types of cone photoreceptor cells. Other animals may be tetrachromats (4 cone types), pentachromats (5 cone types) or even hexachromats (6 cone types). Here are some examples of animal vision ranges:
- Bees: Ultraviolet, blue, green
- Birds: Ultraviolet, violet, blue, green, red
- Cats & dogs: Blue, green, red (similar to humans but more sensitive to blues)
- Reindeer: Ultraviolet, blue, green, red
- Snakes: Infrared, red, green (sensitive to a wider range)
- Butterflies: Ultraviolet, blue, green, red
- Mantis shrimp: 12-16 photoreceptor types including UV and infrared!
As you can see, many animals see into the ultraviolet and some see into the infrared wavelengths invisible to humans. Certain birds, insects, fish and shrimp have the most expanded color vision, thanks to their numerous cone cell types.
Tetrachromatic Vision
Tetrachromacy refers to having four cone cell types. This allows animals to perceive many more colors than humans can imagine. It’s estimated that tetrachromats can distinguish around 100 million different color shades! Here are some tetrachromatic animals:
- Birds
- Fish
- Amphibians
- Reptiles
- Insects
Birds have four cone types, so they are tetrachromats. Compared to human vision, bird color perception includes the ultraviolet range. Many birds use UV signals for mate selection and food identification. Butterflies are also tetrachromats, seeing in the UV spectrum. Researchers believe the extra UV cones help butterflies locate nectar in flowers.
True-Color Vision
“True-color” vision refers to an animal’s ability to see the full spectrum of colors unaided. Humans do not have true-color vision, since we cannot see into the UV range without help. Animals with true-color vision include:
- Mantis shrimp
- Butterflies
- Birds
- Bees
- Many fish & reptiles
Butterflies and mantis shrimp have some of the most expansive true-color vision. Their numerous photoreceptor types allow them to sense an incredibly wide spectrum of light invisible to the human eye. Birds also see the full true color spectrum, with added perception in the UV range.
Better Color Vision in Nature
There are a few reasons why many animals have superior color vision compared to humans:
- More cone cell types allowing perception of more color wavelengths
- Higher total number of cone cells
- Increased light sensitivity
- Enhanced ability to distinguish between similar colors
Tetrachromats and hexachromats have 4-6 cone cell types respectively, compared to humans’ 3. This anatomical difference grants many birds, fish, insects and shrimp a huge advantage in color perception.
Additionally, animals like birds of prey have a higher total concentration of cone cells within a smaller retinal area. This cone density allows raptors to see colors with greater resolution and clarity.
Lastly, some animals have cone cells with higher light sensitivity and broader range. Cats and dogs see better in dim light than humans, and can distinguish subtle color shades more easily.
Colors Only Visible to Animals
There are some colors only visible to animals with higher photoreceptor cones density and true color vision:
- Ultraviolet – Seen by birds, bees, butterflies
- Infrared – Seen by snakes, shrimp
- Combinations of colors – Seen by tetrachromats and hexachromats
One example is avian UV vision. Humans cannot see UV light without technology, while birds use it for social signaling and food finding. Butterflies also use their UV vision to identify nectar guides on flowers. Mantis shrimp likely perceive a stunning array of colors from infrared to UV due to their numerous photoreceptor cones.
Examples of Animal Color Vision
Here are some specific examples of superior color vision in different animals:
| Animal | Color Vision Capability |
|---|---|
| Bees | Can see ultraviolet patterns on flowers that guide them to nectar |
| Mantis Shrimp | Have 12-16 photoreceptor types that detect a huge spectrum from UV to infrared |
| Butterflies | Tetrachromatic vision allows them to find nectar guides on petals |
| Birds of Prey | Increased cone cell density enhances long-distance color perception |
| Reindeer | See ultraviolet reflections not visible to humans |
| Goldfish | Can see infrared light emitted by TV remote controls |
As you can see, many animals have visual abilities that seem super-human. Bees and birds see in ultraviolet, while reindeer use it to find food under snow. Butterflies and mantis shrimp perceive an incredible diversity of colors. Understanding animal color vision gives us a glimpse of how they experience the world.
Advantages of Enhanced Color Vision
Superior color vision provides many advantages to animals in nature:
- Better mate selection – brighter colors attract mates
- Improved food identification – aids in finding fruits, flowers, prey
- Enhanced predator detection – see camouflaged predators sooner
- Increased safety of offspring – utilizing UV or strange patterns
- Improved navigation – certain colors guide migration or pollination routes
UV signaling is a key one – it allows birds and insects to communicate using colors humans can’t perceive. Tetrachromatic insects locate the most nectar-rich flowers quickly. Predators like mantis shrimp spot camouflaged prey with ease. Overall color vision allows animals to thrive in their environment.
Human Limitations in Color Perception
Compared to many animals, humans have limited color vision for a few key reasons:
- Only 3 cone cell types compared to 4-6 in other species
- Cone cells lack sensitivity to UV and infrared light
- Lower total cone cell density than birds of prey, for example
- Narrower range of color perception
- Unable to distinguish subtle differences between similar colors
Humans completely lack the ability to see UV light without assistance. We also cannot perceive infrared wavelengths. Our cone cells adapted to be most sensitive to visible light between violet and red. With only 3 cone types, humans are limited to a narrower spectrum of color compared to tetrachromats and hexachromats.
Enhancing Human Color Vision
While evolution honed human color perception for survival, we now have technology to enhance our vision:
- Ultraviolet photography – Captures unseen UV patterns
- Infrared photography – Reveals unseen IR light
- Spectral filtering – Isolates specific color wavelengths
- Digital enhancement – Software improves color separation
- Bionic contact lenses – Experimental UV and IR enhancement
Spectral photography uses filters to image UV patterns attractive to birds, bees and butterflies. Digitally boosted photos help us distinguish subtle color variation like other animals. Future bionic contacts could let humans see into the infrared or ultraviolet ranges!
Conclusion
In summary, many animals have superior color vision compared to humans. Our vision is limited to a narrow red-violet color spectrum. Meanwhile, birds, insects, fish and other species see an expanded range including ultraviolet and infrared wavelengths. This is thanks to their higher number of cone cell types, increased cone density, and light sensitivity advantages. Tetrachromatic and hexachromatic animals can perceive up to 100 million more colors than we can imagine! Evolution shaped animal color vision to provide key survival benefits in nature. With the help of technology, humans are now discovering how the world looks through the stunning true-color perception of other creatures.
