Rudolph not the only red-nosed reindeer
Rudolph may not have been the only red-nosed reindeer, according to Swedish researchers.
The study used thermal imaging cameras to capture the heat coming from reindeer as they graze.
While most of the animals' bodies were well insulated by their fur, their noses glowed bright orange in the images due to the large amounts of heat they released, the researchers found.
Reindeer have a high concentration of blood vessels in their nose and lips to help keep them warm when rummaging through snow as they search for food.
In some cases these even led to the animal's snout taking on a reddish colour in the cold, Professor Ronald Kroger, a zoologist at Lund University in Sweden, said.
"When reindeer are feeding, their [snouts] are exposed to very low temperatures as they look for food under the snow.
"They need to maintain sensitivity in order to know what they're actually eating.
"They pump warm blood into the [snout] which means it can be a bit reddish because of this strong blood flow."
The story of Rudolph, the reindeer with a glowing red nose, dates back to a book written in 1939 by Robert L May.
Kroger's findings are part of an attempt to understand the physiology of animals in ways not visible to the human eye - and some noses are more of a puzzle than others.
"Dogs are the exact opposite to reindeer," Kroger said.
"Nobody knows why their noses are cold and why they have evolved that way. That is what we want to find out."