Rudolph the fictional reindeer was famous for his oddly colored nose, but his true-life cousins have eyes that change color depending on the season.
In the summer, an interior part of the eyes of Arctic reindeer appears gold, and around Christmas it turns a deep blue, biologists have discovered. It’s not holiday magic, but rather a unique adaptation that helps these animals deal with the strange light conditions at the top of the world.
The reindeer’s world is one of extremes. Above the Arctic Circle, Christmas falls in the midst of a 10-week period of perpetual twilight in which the sun never rises and the landscape is cast in bluish hues. But from mid-May to late July, the sun never sets, creating a long, endless day.
Biologists at the Norway's University of Tromso, in one of the largest cities situated north of the Arctic Circle, wondered how the reindeer managed the transition from a world of near-total darkness to one of blinding light, when springtime sunlight reflects off still-unmelted snow.