Rudolph the blue-eyed reindeer knows best
Turns out there’s a scientific advantage to ‘a very shiny nose’ — especially if it’s red
CONCORD, N.H.— Everyone knows Rudolph has a red nose, but what about his eyes?
Prompted by questions from his 4year-old daughter, Dartmouth College anthropology 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.
Dominy, who specializes in primate vision, was already familiar with recent research on reindeer eyes when his daughter asked him about Rudolph’s nose. Scientists in Great Britain have discovered that, 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. But in reindeer, the tissue changes from a golden colour during the summer to a deep blue in winter.
“What happens is that at night, the animals are trying to dilate their pupils to allow as much light into the eye as possible, and because those muscles are so active, it actually blocks little valves in the eye,” Dominy explained.
“The pressure in the eye builds up and compresses that tissue in the back of the eye, which causes the refractive properties to change.”
While that change could boost an animal’s ability to spot food in the snow when Arctic daylight is dim and purplish, it would be a distinct disadvantage on a foggy Christmas Eve because fog blocks blue light, Dominy said. Enter the red nose.
Of all the colours, red light travels through fog fastest, making it ideal for guiding Santa’s sleigh. But there’s also a downside to red noses, he warns.
Other researchers have discovered that reindeer noses have a complex system of tiny blood vessels that prevents them from freezing but also results in a loss of body heat.
“That’s bad. You want to retain as much heat as possible. If Rudolph has a very bright, glowing nose, he must have an unusually rich microvascular system and he’s probably losing a ton of heat through his nose,” he said. “So Rudolph, more than other reindeer, is probably risking his life by losing so much heat.”