An astrophysicist and an eye expert teamed up to solve the mystery of how and why reindeers’ eyes switch from yellow to blue in wintertime.
On Christmas Eve, a team of reindeer will crisscross the sky towing Santa and his present-laden sleigh.
But Rudolph’s team won’t be the only reindeer doing something special. Back in the highest Arctic, their cousins will be performing an optical feat not observed elsewhere in the animal world: changing their eye structure to better find food and escape predators during the long, dark months of polar twilight.
In the summer, reindeer’s tapetum lucidum—a mirror-like layer at the back of their eye—is a luminous gold streaked through with turquoise, iridescent like a golden opal. But in the winter, that layer turns a deep, rich blue.
Scientists have spent years untangling the mystery of why and how