What color is it?
A long time ago, I was leading a group of college students on a field trip to the Mojave Desert in California. We were walking in a sort of single file line down a steep little ravine, with me in front. Suddenly a black-tailed jackrabbit (Lepus californicus) burst from beneath a bush and darted in front of us. We all saw it. I said something profound like “Hey, look! A jackrabbit.” Then one of the students said “Oh my gosh. What color is it?” There was an awkward silence, after which one of the other students said “Oh my gosh. What sort of a question was that?” Everybody laughed, including the student who posed the weird question. While it is true that animals with dichromatic (so called “black and white”) vision, including humans with color blindness, sense colors differently than do animals with full-color vision. But, even if the perceptions are different among these animals, it seems that they would never actually be unsure of what they were seeing. Is that not correct? I have not stopped thinking about that student’s comment, even after all these years. Maybe the student was much more brilliant and insightful than we all credited at the time?
It all got me to thinking about situations where the color is not as it seems, and maybe we cannot always determine the color of an animal before us? Context appears to make all the difference. Imagine a yellow warbler (Setophaga petechia). They are inarguably, ummmm…..yellow! Well, maybe not? There is no color where there is no visible spectrum light. So, a yellow warbler in cave or truly zero-light room is simply not yellow. It is colorless. (Not the be confused with transparent—that is another phenomenon that does not exist in the absence of visible-spectrum light.)
Let’s move on to another, more real-life scenario. What color is a red snapper (Lutjanus campechanus)? I hope you did not say “red”! Red-light wavelengths do not penetrate very deeply through water, essentially disappearing at about 40 feet. Red snappers typically are found between about 30 to 620 feet deep. Consequently, we can posit that the vast majority of red snappers spend the vast majority of their time at depths where they are not—indeed cannot be—red in color. Color only exists where visible light can be neurologically perceived by an organism. One cannot perceive what does not exist, such as any color in a cave or the color red at 100 feet depth. So, our perception of red coloration on the snapper is what we see when we regard the fish at the surface of the water (or in shallow water). In those contexts, the fish is red. In real-life, however, the fish is essentially gray. I cannot answer your next question: “Well, then, Captain Smartypants, then why do they appear red at the surface if it cannot have much, or any influence, on their actual lifestyle and survival in the deep?” I cannot answer the question in the sense that you are challenging me; I can only revert to the inarguable fact that at or near the surface, these fish indeed are red.
Coral snakes (genus Micrurus) are more complex situation. Everybody assumes that the bright coloration, usually including red and yellow, is to warn away potential predators. There is plenty of evidence to suggest that this is true, applying as well to the snakes that appear to mimic coral snake patterns. But, there is another layer. Few people, including herpetologists, have really spent a lot of time with coral snakes. They are very shy and quick, often nocturnal, and just difficult to observe in the wild or even in human care. They usually are encountered in brush or leaf litter in heavily canopied forests. Under these low-light conditions, the red coloration is greatly subdued for reasons similar to the red-snapper scenario. You already know this phenomenon, because you know that stop signs at night are not red. They are dark gray, until the headlights hit them and they appear red.
Another trick on the coral snake’s palette (pun intended!) capitalizes on a visual phenomenon known as flicker fusion. When contrasting swatches of color are moved rapidly, the individual colors disappear and fuse into a neutral gray-tone. This is the same phenomenon that makes hubcaps appear so differently when spinning versus still. In coral snakes, the alternating bands of black, red, and yellow flicker-fuse into a dull gray when the snake is moving quickly. Add the usual low-light situation, and the effect is magnified. Like the red snapper, coral snakes are brightly colored in certain situations, but appear as a dull gray in the situation where most animals would actually encounter them.
What color is it?!
Indeed, I think that student made a valid question.
Joe Mendelson, PhD
Director of Research