"Rudolph’s red nose may have gone down in history, but research says it was probably his shining blue eyes — a common trait among reindeer — that helped keep him and the rest of Santa’s herd nourished.

A new study suggests that the hoofed mammals’ unique eyes, which glow a vivid blue when illuminated in colder months, may be a result of the species evolving so they can more easily find food during dark Arctic winters.

“Reindeer have just an amazing visual system,” said Nathaniel Dominy, the study’s lead author and a professor of anthropology at Dartmouth College. “It’s unlike any other mammal we know about.”

Similar to other animals, like cats or deer, the ungulates have light-enhancing tissue in their eyes, known as tapetum lucidum. But in reindeer, the luminescence changes color from a golden color in the summer to blue in the winter."

Allyson Chiu reports for the Washington Post December 18, 2023. [2]