Why Is Rudolph's Nose Red, and Does It Really Glow?

Everyone who celebrates Christmas knows the story of Rudolph, the Red-Nosed Reindeer. You'll even find him in Christmas displays, usually with a red light bulb for a nose. Flying reindeer are odd enough, but could one actually have a nose that acts as a beacon? Looking into the natural world, the answer is yes!

Rudolph in Song
The clues we have to Rudolph's appearance come from a song written by Johnny Marks in 1948, and the original book, written by Robert L. May for Montgomery Ward in 1939. In May's original book, Rudolph is an average reindeer with an illuminated red nose. Santa notices the glow while delivering presents to Rudolph's house and drafts Rudolph to guide him through thick fog that threatens to stop Santa's Christmas Eve deliveries.

In the song, there are a few lines that describe Rudolph's nose:

Rudolph, the red-nosed reindeer
had a very shiny nose.
And if you ever saw it,
you would even say it glows.

"Shiny" could mean metallic or bright, but a later line confirms that Rudolph's nose lights up:

"Rudolph, with your nose so bright,
won't you guide my sleigh tonight?"

Bioluminescence
Believe it or not, there are animals in the world that can make their own light. Fireflies are one example that many people see every summer. The ability of a creature to create light is called bioluminescence; creatures with this ability are called bioluminescent.

Most bioluminescent animals live deep in the ocean, where there is no sunlight. Some fish, like the angler fish, have a bioluminescent projection on their bodies that they use to lure prey. These fish use chemical reactions to create light. It is known as cold light, because very little heat is given off, unlike a lightbulb that burns hot.

While green and blue are the most common bioluminescent colors, a few creatures can create red light. One example is the Black Dragonfish, which creates a red light that illuminates its prey in the ocean depths.

Some land-dwelling plants and mushrooms can also glow. Along with fireflies, there are glow worms, spiders and millipedes that are bioluminescent. Foxfire is a natural phenomenon caused by mushrooms that glow under the right conditions. Around 40 species of mushrooms have the ability to generate light.

Mutation
While you won't find bioluminescent reindeer at the local zoo, that doesn't mean they don't exist. All it takes is a single mutation, which is a sudden genetic change in an animal that alters its appearance or abilities. Mutation is the catalyst for animal evolution; it occurs randomly, but if the results give the animal a better chance of survival, the mutation gets passed along to the next generation and so forth.

It's possible for any animal, at any point in time, to develop a bioluminescent red nose, just like Rudolph's.

How Does Rudolph's Nose Work?
Inside the skin of Rudolph's nose are thousands of tiny cells called photocytes. Nerves trigger these cells to release an enzyme that reacts with another enzyme and oxygen to create light. Rudolph may be able to turn his nose on and off, simply by thinking about it. Many bioluminescent creatures have this ability.

Based on the song and story, however, it seems more likely that Rudolph's nose is lit up all the time. That doesn't mean he can't control it; by opening and closing the photocytes in his nose, Rudolph can make the glow brighter or dimmer. That's good news for Santa when the fog is thick.