How can you find delicious food in the snow?Ask the reindeer

There are many myths about reindeer, and at least one of them is true: they live in remote areas in the north, where there’s a lot of snow.

Living in that winter wonderland can be a challenge when your favorite food is white, but animals have special eyesight that may help them find food more easily, which can be especially handy after a busy Christmas Eve.

“When I learned that caribou had a very unusual visual system, I thought, this must be an adaptation for finding food,” said Dartmouth College anthropology professor Nate Dominy.

Domini studies how animals find and eat food.A study published last week in the journal i-perceptionLater, he and his colleagues found more evidence to explain the reindeer’s strange vision.

Looking for food under ultraviolet light

Scientists have long known that reindeer have special vision that allows them to detect ultraviolet light that is harmful to human eyes.

“For unknown reasons, UV rays can pass directly through these tissues in reindeer and come into contact with the retina,” Domini said.

One possible explanation for this is to protect them from predators.

“For us humans, it’s difficult to see white wolves in the snow, but for reindeer, it can be a completely different story because snow reflects UV rays, while wolf hair absorbs UV rays,” he said. “So, to reindeer, wolves look much darker than they look to us.”

This also applies to finding food. Reindeer are large animals that require a lot of energy, but their diet consists mainly of organisms called lichens, also known as reindeer moss.

“Lichens are an amazing life form. It’s a symbiotic relationship between algae and fungi,” Domini said.

But some lichens are white and become covered with snow in the winter. So in this study, the team focused on the specific lichens that reindeer eat. They wanted to see how the interaction of organisms with light affects how reindeer see them.

Just like wolves, lichens absorb UV rays, while snow reflects them, Dominy explained. So, for reindeer on the prowl in search of food, the lichen stands out against the white snow.

“If you were a reindeer and you could scan the distance, you could see a patch of edible lichen in the distance, so you wouldn’t have to wander around,” he said. “You can move in a straight line, save energy, reach the food resource and eat it.”

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The team studied different lichen populations in Scotland. Their results provide evidence for previous hypotheses that the reindeer’s eyes have adapted to their environment and are able to find food more easily.

“So we can prove [lichens] Is it true that there are strong absorbers of ultraviolet rays, and many vegetation? So we just confirmed that lichens are a reasonable explanation for their UV vision,” Domini said.

Extra help from adjustments

One more thing that helps reindeer: An extra layer in their retinas adjusts to become more sensitive to UV rays when it’s snowy and dark in the winter.

Robert Fosbury, a retired astrophysicist who now studies the relationship between light and life, said that extra layer is common in many animals, but its variability is not.

“Reindeer vision is very special because it’s really the only animal known to have significant changes in visual abilities between winter and summer. Of course, this is especially important in the Arctic,” he said.

This is because greater sensitivity to UV rays means better vision, making it easier to hide from predators or find food.

There is still more to learn about reindeer eyes, such as whether eating these lichens can protect them from potential damage from ultraviolet light. In the meantime, Domini says one sure way you and your child can maintain exceptional eye health is by taking vitamin C, which has been shown to protect eyes from UV damage.

“When people studied reindeer eyes, they found that reindeer eyeballs contain a lot of vitamin C, so this is another way to protect the eyes,” he said.

So if you want to pack some snacks for the reindeer that might visit your home, orange juice or carrots and Santa cookies are great options.

Katherine Fox and Gabe Spitzer contributed to this report.