How do you find delicious, white treats in the snow? Ask the reindeer

AILSA CHANG, HOST:

So there are a lot of myths about reindeer, and at least one or more of them is actually true. They live in remote areas way up north that get a lot of snow. And, you know, living in that winter wonderland can be a challenge if your favorite food is white. But it turns out reindeer have special vision. Now, scientists have known for a while that reindeers' vision is special, but recently they have discovered more evidence as to why.

NATE DOMINY: When I learned that reindeer have a very unusual visual system, I thought, well, that has to be an adaptation for finding food.

MARY LOUISE KELLY, HOST:

That is Nate Dominy, professor of anthropology at Dartmouth College. He studies how animals find and eat their food. He says reindeer eyes can detect ultraviolet light, the type of light that can be harmful to human eyes.

DOMINY: One idea is that the reason why reindeer have this special visual system is to see their predators - wolves, mainly. So to us, to humans, a white wolf on a snowy landscape would be difficult to see. But for a reindeer, it could be totally different because snow reflects ultraviolet light and wolves, the hair on wolves, absorbs it. So for a reindeer, a wolf would look much darker than it does to us.

KELLY: Their special eyesight also applies to finding food. You see, reindeer are big animals. They need a lot of energy. But surprisingly, their diet consists mostly of organisms called lichens, also known as reindeer moss, which are white.

DOMINY: Lichens are this amazing life form. It's a symbiotic relationship between algae and fungi.

CHANG: In a study published in the journal i-Perception, Dominy and his colleagues focused on the particular lichens that reindeer eat to see how their interaction with light affected how the reindeer would see the lichens. Dominy says that, like the wolves, lichen absorb ultraviolet light while the snow reflects it. So for reindeer looking around for food, the lichens pop out against the white snow.

DOMINY: If you're a reindeer and you could scan the distance and you can see way over there, there's a patch of edible lichens, then you don't have to wander around. You can move in a straight line, conserve energy, get to that food resource and eat it.

CHANG: Robert Fosbury is a retired astrophysicist who now studies the relationship between light and life. He's had a chance to look at this new study, and this is how he describes what reindeer will see on the tundra.

ROBERT FOSBURY: They will actually be able to see different lichen as different colors, and I think that may help them select their food source.

KELLY: This research offers more proof for how reindeer developed their super vision, but there is still more to learn about their eyes. In the meantime, Nate Dominy says, if you and your kids want to help keep those special eyes healthy, vitamin C may work.

DOMINY: When you want to give treats to reindeer visiting your house, orange juice could be a great treat, or carrots could be a great treat.

CHANG: So cookies for Santa and orange juice for his reindeer.

(SOUNDBITE OF PIANO PROJECT'S "RUDOLPH THE RED NOSED REINDEER") Transcript provided by NPR, Copyright NPR.