Concord, New Hampshire— Rudolph the Red-Nosed Reindeer may have millions of carrots ready for him on Christmas Eve, but what about the rest of the year?
Finding food in cold, barren lands is a challenge, but researchers at Dartmouth College in New Hampshire and the University of St. Andrews in Scotland report that reindeer eyes may have evolved to allow them to spot themselves easily Favorite food.
Dartmouth anthropology professor Nathaniel Dominy said this is further evidence that while reindeer are best known for pulling Santa’s sleigh, what really sets them apart is their vision.
He said in an interview that they have been obscure and unknown in the annals of visual neuroscience, but they are having their moment because they have very fascinating visual systems.
Scientists have known for years that the mirror-like tissue in reindeer eyes changes color from green-gold in summer to bright blue in winter, a process thought to amplify the low light of polar winter. But they didn’t know what to make of another strange fact: Unlike other mammals, reindeer can see light in the ultraviolet spectrum.
Most animals that are active in daylight conditions want to avoid UV rays. UV rays are destructive, Dominy said. Snow reflects UV rays, which is a problem and is why humans suffer from snow blindness.
Some scientists believe that reindeer’s vision evolved to protect the animals from predators, allowing them to spot white wolves in snowy landscapes, for example. The new study points to another possibility: food.
Reindeer live primarily on light-colored reindeer moss, which is not actually a moss but a type of lichen that grows in crunchy, carpet-like patches in northern latitudes.
The researchers traveled to the Cairngorms in the Scottish Highlands, home to more than 1,500 species of lichen and Britain’s only reindeer herd. They found that reindeer moss absorbs ultraviolet light, meaning the white lichen, which is difficult for humans to see in the snow, appears dark on the animals.
If you’re a reindeer, you can see it and you have an advantage because then you’re not wandering around in the landscape. Domini says you can walk in a straight line to eat food and save energy in the process. These animals are hungry for food, and if they can find enough lichens, they have an advantage.
Juan José Negro specializes in evolutionary ecology and conservation biology at the Spanish Scientific Research Council. Although he focuses primarily on raptors, he finds the new caribou research interesting.
“I love every piece that involves color and visuals,” he said. Every time I read someone else’s work, new ideas are inspired. As far as reindeer are concerned, this makes me want to focus more on this part of the spectrum.
He said that while he doesn’t think the research will have immediate biomedical benefits, this type of work can help further our understanding of how animals cope with difficult environments.
Domini agrees, but says it also has implications for humans. Due to their antioxidant properties, lichens have been extensively studied pharmacologically. Reindeer’s eyes allow ultraviolet light, suggesting there may be some mechanism that protects them from harm, he said.
Reindeer eyes are rich in ascorbic acid, or vitamin C, which is very effective in repairing damaged cells, he said.
With that in mind, Domini is updating his recommendations following a 2015 paper that explored why reindeer’s red noses are ideal for guiding Santa’s sleigh.
At the time, he suggested that the kids leave out Rudolph cookies and other high-calorie foods to make up for the body heat he was losing through his nose. Now, he said, focusing his eyes on leaving the milk and cookies for Santa.
He said that in order to protect eye health, it is best to feed them something rich in vitamin C. Orange juice and carrots are the perfect food for reindeer on Christmas Eve.
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