What Colors Do Animals See?
This is a question that has plagued researchers for a long time: how do different animals perceive color? A team of biologists from the University of Arkansas recently brought us closer to understanding the world through the eyes of the creatures we inhabit the planet with. The broad conclusion was that it isn’t uniform — how animals see color depends on their environment. Terrestrial animals can see more colors than animals adapted to water, and animals in open terrestrial habitats see a wider range than those in forest habitats, they concluded.
There’s also evolutionary differences at play: invertebrates see differently compared to vertebrates. The former are able to see shorter wavelengths of light, as compared to the latter.
But this conclusion itself was no mean feat to arrive at. There is much we can determine about animals based on what we see of them, but how do we see what they see? “Scientists have long hypothesized that animal vision has evolved to match the colors of light present in their environments… Gathering data for hundreds of species of animals living in a wide range of habitats is a monumental task, especially when considering that invertebrates and vertebrates use different kinds of cells in their eyes to turn light energy into neuronal responses,” Erica Westerman, who co-authored the paper published on Monday in Proceedings of the Royal Society B, said in a press release.
The researchers conducted a systematic review of animal vision data of 446 species — spread across four different phyla. One of the phyla contained vertebrates, while the other three contained invertebrates like insects, jellyfish, and other animals. Their findings opened up more questions about animal vision — they found that while habitats do influence how many colors they see, they’re also constrained by evolution. Vertebrates and invertebrates both use a cell type called “opsins” to see — but these are formed through different physiological processes that determine which wavelengths of light a creature can see.
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But the question of color vision in animals is also a humbling endeavor, for it puts our own view of the world in perspective as just one among many points of view. It also shows why any organism is able to perceive color at all, and how it helps creatures organize their lifespans and worlds. Many use color information for the essentials — food, mating, and navigation. Previous research, for instance, has shown that bees see the world five times as fast as humans do, and they have the fastest color vision of all animals. “Bees were the first animals that scientists proved to have color vision, and they have since been shown to put it to good use; navigating dappled light and shady areas, recognizing shapes like their hive entrance, and particularly for finding nectar-bearing colo
ured flowers,” researchers from the past study noted.
Another study discovered that frogs and toads can see color in extreme darkness, giving them the best night vision of all animals. It turns out that they have two special sensitivities of “rods” — or optical cells that allow us to navigate low-light conditions — and it allows them to escape traps, mate, and look for food in pitch darkness.
And then there are those that can see colors we can’t perceive. Reef fish, including clownfish like “Nemo” for instance, can see ultraviolet light that we shield ourselves from. “Ironically, as the colo
urs of the reef change and disappear because of climate change, we are just beginning to understand how reef inhabitants see and experience their vibrant world,” said the researcher from this study. The implications for knowing how animals see, then, apply to us too — our actions may be influencing how others get to see their worlds, and in turn, change their very life cycles.
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Reindeer have this ability too. Their ability to see in UV light gives them access to a range of information that ensures their survival: “When we used cameras that could pick up UV, we noticed that there are some very important things that absorb UV light and therefore appear black, contrasting strongly with the snow. This includes urine — a sign of predators or competitors; lichens — a major food source in winter; and fur, making predators such as wolves very easy to see despite being camouflaged to other animals that can’t see UV,” said researchers of one study.
Hummingbirds, too, have a dazzling array of color vision that we can’t even imagine: they possess a fourth “cone” — optical cells that perceive light — that allows them to see UV light too. What’s more, they can see brand new colors this way, such as ultraviolet + red, and ultraviolet + green. These are known as “non-spectral” color combinations — they arise out of colors far apart from one another in the visible light spectrum combining. Humans can only see one, and that’s purple. But hummingbirds can see up to five.
Other creatures have an entirely different relationship with color than we’re familiar with — peppered moth caterpillars, for example, perceive colors through their skin. They use this ability to find the best environment to camouflage in — in this case, the ability to sense color can be lifesaving.
But some animals see the world in just shades of blacks, whites, and greys — these include whales, sea lions, and some bat and mice species. Elephants and dogs have vision that is similar to color-blindness in humans — they can’t tell greens and reds apart. Overall, environmental necessity and evolution determine how each creature sees, and to what extent.
Ultimately, the question of how animals see color isn’t a singular one — but the more we know about the sheer possibilities of vision, the more we begin to understand our own role in shaping the ecology of the beings we share this planet with. Knowing, then, is key to co-existing — and all it takes is a little perspective.