There are some fantastic people over on twitter asking brilliant questions to explore science and the world with. Four such questions are from Marthy – and we’re going to have a look at the first question “why is Rudolph’s nose red?” in this Christmas Eve post!

Here are the questions:

Marthy’s questions:

  • What makes Rudolph’s nose red?
  • Why would a red nose help Santa?
  • What is the best food to give to a reindeer?
  • Why do reindeers eyes change colour?

Rudolph the red-nosed reindeer

Rudolph first appeared in 1939 – making him an 83 year old reindeer! He’s still very spritely for his age, so presumably there is some Santa magic going on here. He’s described as having a luminous red nose that other reindeer laugh at him about – very cruel! Until one Christmas Eve Santa can’t see through the fog to guide his sleigh and deliver all the presents around the world… and the hero of the night? Rudolph – with his nose so bright – helps to guide the sleigh alright.

So that should be enough to answer our question. What do we know so far?

Rudolph is a reindeer, with a nose that glows red, and it is bright enough to help guide a flying sleigh through foggy conditions.

What is the brightest red animal?

Being a reindeer, Rudolph probably hasn’t got a degree in electrical engineering, so we can assume that the light in Rudolph’s red nose is biological rather than battery-powered! Unless of course, Rudolph snorted a bunch of lightbulbs… let’s assume not.

A good place to start then is to look at bright red animals and see how they do it.

Red animals

brown white and orange small bird perched on wood near pine tree leaf


Our first contender for the brightest red animal has surely got to be the Robin Red-Breast, right? That brightly coloured face and chest are a symbol of Christmas and I bet you all have a Christmas card somewhere in your house with one of these festive fellas on it.

This article from Science Focus suggests that the red chest is a symbol of how old and strong a male robin is! Each year they survive a winter their chest gets a little bit bigger and a little bit more red. So a giant fluffy bright red chest is like a medal on display.

Sometimes the colour in bird’s feathers are nothing to do with the chemicals in them (like the colours in paints and inks) but more to do with the incredible detail of the feather’s structure itself.

Since Rudolph’s nose has no feathers, we can rule this option out.


Our next option is a butterfly. These beautifully-patterned bugs show many different colours at the same time. Their wings contain lots of pigments – like the inks we write and draw and paint with – that can make some colours like yellow.

Where butterflies get really clever is to combine these pigment colours with an incredible scientific effect called iridescence (pronouned e-rid-ess-ence) that can change how the colours look when the light hits them at different angles. That can make the patterns look like they are shimmering and glittering and moving! Combining iridescence with pigmentation can create some beautiful red patterns.

If you remember, Bambi was definitely good at attracting butterflies to his nose and he was a deer – so is it possible that the red colour on Rudolph’s nose could come from butterflies?

Well.. at night time we don’t look out of our windows and see glowing red points of light flashing about as butterflies go to bed, do we? They might be a bright red colour, but they don’t glow like Rudolph’s nose does in the song.

close up of a butterfly on flowers
a glowing jellyfish

So where does that leave us? We can get the right colour, but it doesn’t shine like a lightbulb


There are some animals that can glow and produce light for themselves. Think of things like glowworms or fireflies.

Most of these glowing animlas live deep down in the sea where the sunlight can’t reach – so they have to make their own light!

Some tricky animals use this light to lure in prey to snatch from the dark… others use it to find food. Some probably just think it looks pretty. Some probably do it totally by accident!

Surprisingly, some animals actually produce glowing lights to hide themselves as a form of camouflage! Imagine if you were standing in front of a lightbulb – people would be able to see you as a big dark silhouette in front of the light. This also happens if you are deep down in the sea and look up towards the bright light from the sky – you might see the shadow of an animal above you! These clever animals emit light on the undersides to make up for the light they are blocking! Imagine turning on a torch to make hiding better… The world is a strange place sometimes.

Now.. there is actually an animal that can glow bright red. That might be useful for our search for Rudolph’s bright red nose.

Black Dragonfish

The brightest, glowing red animal is a deep sea fish called the Black Dragonfish. This is a very cool name which partly makes up for this animal being so desperately ugly.

It has a bright red glowing patch underneath its eye.. near to where a fishy nose might be! Perhaps we have our answer.

Image credit: By ESRI, Dr. Beinart, Tracey T. Sutton – ESRI, Dr. Beinart Powerpoint Lecture, Tracey T. Sutton Article: Trophic ecology of the deep-sea fish Malacosteus niger (Pisces: Stomiidae): An enigmatic feeding ecology to facilitate a unique visual system?, CC BY-SA 4.0,

A black dragonfish - a dark black fish with a bright red splodge underneath its eye.

Rudolph’s Bioluminescent Red Nose

Since the Black Dragonfish can’t survive outside of the deepest parts of the ocean, and there aren’t many chimneys for Santa to go down in the black wet depths, the Black Dragonfish can’t do much to guide Santa. Perhaps Rudolph has learned a trick from this slippery sole* and that’s how his nose glows so bright he can guide a Sleigh through a foggy night.

How does luminescene work?

There is an important chemical involved in bioluminescence – animals making glowing lights – called luciferin. This can be broken down by luciferase (biologists aren’t very imaginative with thier naming, unfortunately) and as that happens little bits of light shine out! Perhaps – if let me know how much you enjoyed this article – we can do a future molecule of the month post about luciferin.

Rudolph the red nosed reindeer - screenshot from a film.

Maybe Rudolph’s bright red nose is a result of luciferin and luciferase, learned from the Black Dragonfish, emitting bright red lights into the sky.

How this might have come about is hard to say..

Perhaps Rudolph’s favourite snack as a child was Black Dragonfish and the colour has sort of.. stuck around?

Or maybe Rudolph has a genetic variation that causes production of these bioluminescent molecules by accident?

The other option is that Santa used CRISPR to genetically engineer (check out our article all about this) a special reindeer with these luciferous noses specifically to make his foggy Christmas journies safer, brighter, and more jolly.

I doubt any of you will be eating Black Dragonfish for Christmas dinner… or reindeer for that matter… but as you are opening your presents and enjoying the festive cheer tomorrow, spare a thought for Santa and his reindeer putting their feet and hooves (respectively) up and having a rest. As you do – thank bioluminescence for making Rudolph’s nose so bright!

The next question – why would a red nose help guide Santa – will be written and posted as soon as I get a chance. In the mean time, Merry Christmas!

*Pun warning, apologies.



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