If you come across a reindeer in the summer, you may notice its eyes are golden, however, if you meet the same reindeer in the winter you would notice its eyes changed to a winter blue. Why?
Neuroscientist Glen Jeffery investigated a collection of reindeer eyes from the Arctic and what he found was an astonishing discovery. The retina, located on the back of reindeer eyes, contains light-sensitive cells. The light that is reflected from reindeer eyes is related to the spacing of collagen fibers in the reflective layer so in the winter the pressure inside the eye increases allowing the collagen to compress the fibers together to allow the reindeer to capture more light during the dark winter months in the Arctic. The reduction of space between the fibers causes the retina to reflect bluer light. In the summer, since the Arctic has continual sunlight, reindeer are able to reflect more light from their retina, making the retina appear gold.
So far, Arctic reindeer are the only mammals discovered to have changes to their retina due to seasonal changes of light. Scientists are now researching whether or not the changes to their retina has an effect on their ability to see ultraviolet light.
Learn more about animals and their winter climates at Arizona Science Center’s Snow Week, now through January 1!