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Rudolph the blue-eyed reindeer?

Reindeer eyes - Credit Glen Jeffery
A British and Norwegian study published Wednesday shows that Arctic reindeer are the only animals that can shift their eye colour depending on the season. Two reindeer eyes, one from summer and one from winter, are shown above. (GLEN JEFFERY PHOTO)

From the "holy crap, nature is the coolest" desk comes a study showing that Arctic reindeer change their eye colour from summer to winter.

And we're not talking light brown to lighter brown. British and Norwegian scientists writing in Proceedings of the Royal Society B discovered that the animals eyes are golden in summer but turn deep blue in the depths of the Arctic winter.

The researchers suggest the switch is a way of coping with the continuous daylight of polar summers and the continuous darkness of the polar winter. Arctic reindeer are the only animals ever discovered to have this handy trick.

Most animals have a layer of tissue in their eyes called the tapetum lucidum. The TL lies behind the retina and directs light back out through it, enhancing night vision.

In summer, the TL in reindeer reflects most of the light it absorbs back out through the retina. But when their eyes turn deep blue in winter, they reflect less light out, increasing retinal sensitivity. That shift means a loss of vision sharpness, but the increased sensitivity could help them avoid predators in the everlasting Arctic night.

And here the rest of us are getting through winter with Netflix and stiff cocktails.

Kate Allen is the Star's science and technology reporter. Find her on Twitter at @katecallen.


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