Pennsylvania Game News - December 2012 - 64
ATE WORD has arrived from the frontiers of science — reindeer aren’t like you or me. No, they don’t fly, even if the season is right for it. Researchers in the U.K. have discovered that reindeer — the Old World version of North America’s caribou — can see quite well in the ultraviolet (UV) range, wavelengths that are invisible to humans and to most other mammals. It turns out that in the dim, near-darkness of the snow-draped Arctic winter, ultraviolet light abounds — and it makes many things of profound importance to reindeer much more easily visible. “When we used cameras that could pick up UV, we noticed that there are some important things that absorb UV light and therefore appear black, contrasting strongly with the snow,” said lead scientist Glen Jeffery of the Biotechnology and Biological Sciences Research Council. In UV light the lichens that reindeer eat stand out in the snow — as does the fur of wolves, their main predator, even those that are as white as the drifts. This discovery poses a few questions, including how reindeer are able to ward off snow-blindness, a painful hazard to human travelers in the Far North that is caused, in large measure, by overexposure to UV light. But it also serves as a reminder that the world we see is not the same one that even the humblest creatures around us perceive. Birds, for example, have a famous ability to see in the UV range. This is handy for finding food; UV light makes it easier to distinguish ripe fruit, for instance, and UV vision is also good for picking mates. In addition to the bright plumage we can see, many birds have UV pigments to which we are blind, and which play important social roles. It may be that most birds whose sexes look identical to us are anything but to each other. Among half the species of Neotropical cardinals and tanagers, males and females look identical to us; under UV light, however, 97 percent have patches of UV plumage that distinguish the sexes. And while normal humans are trichromatic — able to distinguish three primary colors, whose blending creates the palette of hues we see — other organisms leave us in the dust. Birds, reptiles, amphibians, fish and most arthropods are tetrachromic — possessing four kinds of cone cells, giving them a vastly richer visual world than the one we inhabit. Butterflies and lamprey eels appear to have five color channels, and thus five primary colors, allowing them to distinguish up to 100 billion different combinations. But the chromatic champion is a species most people have never even heard of — the mantis shrimp of tropical reefs. Its eyes are probably the most complex in the world — able to see not just visible and ultraviolet light, but also linear and circular polarized light, and possibly infrared. Most astoundingly, the shrimp can see 11 or 12 primary colors, not the measly three that humans perceive. Sitting at the mouth of its burrow on a tropical reef a mantis shrimp as long as your thumb can see the world in hues that beggar the human imagination — and ought to make us at least a little bit humbler.
64 GAME NEWS
Do You See What I See?