First of all let us explore the question: “How do you even know if an animal can see colour?” This is actually a fairly simple question to answer. Eyes have cones and rods that assist with vision. Rods are responsible for vision at low light levels, but do not assist with colour vision - for that we need cones. So there you have it - if an animal has cones, it can see in colour at least to some degree. What is trickier, however, is figuring out what colours might be seen, and how they will appear to the animal. Will they see sharp images as we see them, or abstract versions of our vision?
The location and number of cones in the retina determine how strong a colour might appear to an animal. Notice I said ‘might’. We cannot really understand what an animal sees, only speculate on what it might see based on our vison and our knowledge of similar species. To illustrate this point, ask your friend or partner to look at a grayish-green wall and ask them to tell you what colour they see. Do they see a gray wall or a green wall? Now ask yourself the same question. The answer will likely not be the same. It is the same with animals – they see colours differently.
So here are a few examples of common animals to give you an idea for comparison. Did you know that many crustaceans (e.g. crabs) can see only blue and red? This makes perfect sense as many are in fact blue and red in colour. If your prospective mate or rival has red or blue colouring, you would want to see that. If they are not rivals, then it does not matter. Octopi can only see blue. What colour is the ink they use to drive off predators? Well, blue! Birds generally see broad ranges of colours. Look at a Cardinal - it has red, black, brown, yellow and orange shades in its plumage. A Blue Jay has blue, black, white and gray. To make sense of them, they need to see all the colours and not just the patterns.
Cats and dogs only see two colours and then only if they are bold, so their world is a combination of pale hues, not black and white but certainly not bold colours.
Our closest allies - chimps, apes and monkeys - see the world pretty much as we do. Rabbits see blues and greens, while one source says squirrels see yellows and blues. I am not sure why, but obviously there is a reason – nature is never random. Any ideas?
Now to complicate this, can some animals see colours or light we cannot even detect? Well, yes, they can. Many animals can see well within the ultraviolet or infrared range. For example, many insects see ultraviolet light, allowing them to see shapes but they may be ill-defined. Rats and mice also see ultraviolet light. Interestingly, their urine is invisible to us (although it may be smelly) but a Kestrel can ‘see’ it and find the prey easily. This ability in birds is actually very well developed. When they see a black bird, such as a Starling, they see a multi-hued purple, green and black iridescent image – humans cannot detect that with our vision. Another adaptation some animals have (e.g. snakes) is to see in the infrared range. This is the kind of images we see in spy movies where the body heat of an individual is clear when one wears special goggles. Many animals can see this as well and obviously it has advantages, especially if they live in low-light environments or are predators looking for prey hiding in the dark.
One last bit of information: When we watch nature shows, they often say that a spider or a bee sees a hundred tiny images of the same thing, because it has so many eyes. Not true! They see one image like we do. Think of your computer screen – hundreds of tiny pixels make up the picture, but we see only one image.
Geoff Carpentier is a published author, expedition guide and environmental consultant. Visit Geoff on-line at www.avocetnatureservices.com and on LinkedIn and Facebook.
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Geoff Carpentier is a published author, ecotour guide and environmental consultant. Visit Geoff on-line, at www.avocetnatureservices.com and on LinkedIn and Facebook.