Reindeer eyes change color with the seasons

Reindeer - no not the magical ones that Santa uses to deliver presents across the world in one night, real Reindeer - have eyes that change color depending on the season. Arctic reindeer are the only known mammals whose eyes change color depending on what season they are currently in. In the summer, when the sun is brighter, their eyes are a bright golden color. In the winter, the eyes are less reflective and turn a dark blue color.