CONCORD, N.H. — Prompted by questions from his 4-year-old daughter, Dartmouth College professor Nathaniel Dominy recently wrote a scholarly paper on how the unique properties of reindeer eyes might explain the advantage of having a very shiny nose, particularly if it produces red light.
Unlike most mammals, reindeer can see ultraviolet light, meaning white polar bears or wolves that absorb UV light would stand out more against a snowy background. Reindeer eyes also include reflective tissue that appears to glow when light hits it — familiar to anyone who’s seen a pet or wild animal illuminated by car headlights. In reindeer, the tissue is a deep blue in winter.
Enter the red nose. Of all the colors, red light travels through fog fastest, making it ideal for guiding Santa’s sleigh. But there’s also a downside to red noses.
“He must have an unusually rich microvascular system, and he’s probably losing a ton of heat,” Dominy said.
