Discoveries

December 25, 2023

Rudolf’s Shiny Eyes

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Forget about the shiny nose: For the reindeer guiding Santa, it’s all about the eyes.

That’s because, during the colder months, reindeer eyes turn from a golden color to a vivid blue that allows them to see in the darkness of winter.

The animals have a special light-enhancing tissue called tapetum lucidum in their eyes that gives them and other nocturnal creatures night vision. Still, scientists have long wondered about the reindeer’s visual acuity because it isn’t a nocturnal creature, and it’s the only animal whose eyes change color.

Now, a new paper has suggested that the hoofed creatures evolved these visual capabilities to be able to easily forage for food during the dark Arctic winters, according to the Washington Post.

A research team conducted a study in the Cairngorm Mountains in the Scottish Highlands, which houses Britain’s only reindeer herd and around 1,500 species of lichen – pale, branchlike organisms that tend to grow in thick beds and resemble shag carpeting.

Reindeer love lichen, even though it’s not very nutritious.

Turns out that the fungi-algae organism is capable of absorbing ultraviolet light, which makes it more visible to the reindeer in snow-covered terrain.

Images taken with filters adjusted to mimic reindeer sight showed the ungulates probably see lichens as dark patches against the highly reflective snow.

“They can see it from a distance and this would give them big advantages because then they don’t have to wander around the landscape looking for food,” said lead author Nathaniel Dominy.

He added that this is the first study to measure the amount of light at different wavelengths that are being reflected from the lichen that reindeer often eat, which also explains the animal’s unusual visual system.

This story originally appeared in the December 25, 2023 newsletter, To the Rescue.