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Arctic migration caused caribou to see in UV

Alaska Dispatch

A new study suggests that Arctic caribou -- a mere 10,000 years after their initial migration to the region -- have adapted to the environment by being able to see in ultraviolet light. NewScientist reports that the study examined the responses of 18 anesthetized caribou to a variety of lights, including a UV light, which evoked a response in every animal. The adaptation is likely the result of the snow-covered Arctic, which the article says can reflect as much as 90 percent of all UV light from above, where non-snowy terrain reflects only a fraction of that. Few mammals can see in UV, including some rats and bats, but the study speculates that caribou have adapted in this fashion because caribou urine and lichens -- which signal potential mates and a major source of food, respectively -- absorb high amounts of UV light, making them stand out as black in the UV spectrum, and in high contrast to the typical white snow that makes up the caribou's natural environment for much of the year. The excess of UV light in the Arctic is what leads to so-called "snow-blindness" in humans. Read more about the study and its implications for human use, at NewScientist.