Why is Rudolph's nose red?

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It's no wonder Rudolph the red-nosed reindeer is the most famous member of Santa's team -- on top of being a skilled flyer, his nose, as his name suggests, glows bright red. This unusual variation on the reindeer nasal prominence could have all kinds of benefits, the most important of which would involve guiding Santa's sleigh.

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Could bioluminescence be the reason behind Rudolph's ruby muzzle? (See Christmas tree images.)

According to folklore, if the weather's ever bad on Christmas Eve, Santa's cleared for flight -- by the FAA, for that matter -- thanks to the brightness of Rudolph's nose.

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But how does Rudolph's nose actually work? How could one reindeer create a light bright enough to lead a sleigh through darkness and inclement weather? And how could a reindeer actually develop a red nose?

Although no one may ever know for sure just how Rudolph got his unusual nose, we at HowStuffWorks have what we think is the most logical explanation for how the doe-eyed deer guides Santa's sleigh: science.

In this article, we'll look at the scientific explanations behind Rudolph's nasal beacon.

No Bull
Although Rudolph is what's called a bull -- a male reindeer -- there's a rumor that many of Santa's reindeer might be cows, or female reindeer. Why is this?

Have you ever seen pictures of Santa flying in his sleigh with his team of reindeer? If you have, you'll notice that the reindeer have fully grown antlers. The interesting thing is, though, male reindeer typically shed their antlers by early December, well before Christmas Eve. The antlers grow back in the spring, and the cycle of growth and regrowth continues. Cows keep their antlers all year long, however, so the chances that there are more females than males on Santa's sleigh are a bit higher.

This isn't to say that all of the reindeer are female and Rudolph's the only guy out there. Most males shed their antlers, but not all of them, and it's possible that a bull won't lose his antlers until after December. Accounts of Blitzen, a part of the original team of reindeer, identify him as Rudolph's father, so we know that Santa has both male and female reindeer leading his sleigh.

Rudolph's Bioluminescence

Rudolph could use something many organisms use on Earth in order to create natural light -- a neat little scientific trick called bioluminescence. Animals can make their own light by mixing certain chemical compounds together to produce a glow. The reasons vary -- fireflies, for instance, flash light at each other in order to attract mates, while some fish that live very deep in the ocean use light to locate prey.

Rudolph could use his bioluminescent nose in order to locate a safe route for Santa's sleigh, but how would it work?

There would be three parts to his nasal beacon. The first would be just like any other reindeer nose (so his playmates technically shouldn't have shunned him from any reindeer games in the first place). He would breathes oxygen through it, and it would be made up of two layers -- the dermis, the thick, inner layer of skin that contains blood vessels and hair follicles, and the epidermis, the thin, outer layer that you can see and touch. The other two parts, however, would set Rudolph apart from all the other reindeer.

The second part is a thin, enclosed layer of a light-producing organ between the dermis and the epidermis. Inside this layer is luciferin, a light-producing substance, and luciferase, an enzyme that catalyzes the light-producing reaction.

The third part is where the "red-nosed reindeer" part comes in. Most bioluminescent life forms, like fireflies, produce green light. The outermost part of Rudolph's nose, however, would be a red phosphorescent layer -- once the light-producing organ started creating light, the phosphorescent part of his nose would absorb the green light and emit a red light.

How would his nose get so bright, though? Bioluminescence often requires another substance, like oxygen, to make light, and Rudolph would breathe lots of oxygen right near the light-producing organs, providing enough reactions for long, intensely shiny bursts of light.

But why is Rudolph the only reindeer with a nose that glows? In the next section, we'll learn about how and why Rudolph has a muzzle like no other.

Rudolph and Evolution

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Rudolph's glowing nose would come in handy in Scandinavia, where there's little sunlight in the winter.

So we know that Rudolph stands out a bit from other reindeer, but how could something like this have happened? Could Santa be some kind of a mad scientist, tweaking reindeer DNA for his own benefit, or could Rudolph's nose be a biological accident?

It's possible that Rudolph's bright honker could be a reindeer atavism. But what's an atavism?

An atavism is a trait of distant ancestors that randomly pops up in modern-day organisms -- a whale with legs or a human with a tail are two examples. These traits may have served a purpose for the animal way back when, but for whatever reason the trait was "silenced" over time, every once in awhile making a rare triumphant return in modern times. Could distant reindeer ancestors of Rudolph have needed to produce light in order to survive in the wild? You'll find most reindeer in Scandinavia, and it does get pretty dark there during the winter -- so could Rudolph's ancestors have needed a better way to get around at night?

But that doesn't explain why only Rudolph has a bioluminescent nose. When we look closer at Rudolph's childhood, however, it could be that his bright nose was a rapid evolutionary adaptation. It's possible that the real reason Rudolph couldn't play in all those reindeer games was due to his poor eyesight -- he developed the red nose in order to compensate, and it just happened to save Christmas when Santa really needed it.

Although his playmates treated him like a misfit in the beginning, Rudolph actually proved himself to be the stronger specimen. Determined to excel, he could have adapted out of necessity. The question now is whether or not future generations of reindeer could also take on Rudolph's unique traits.

For more holiday-related goodness, including Santa's sleigh, Santa's elves and fruitcake, see the next page.

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Why is Rudolph's nose red?