He said: “When reindeer are feeding, their mules 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 mule which means it can be a bit reddish because of this strong blood flow. The thermographic cameras show the heat coming from their body. The eyes and the mule are lighter and warmer than the rest of the body.”
The story of Rudolph, the reindeer with a glowing red nose, dates back to a book written in 1939 by Robert L. May. It has subsequently featured in hundreds of stories, songs and films about the folklore of Father Christmas and his sleigh.
Prof Kroger’s findings are part of an attempt to understand the physiology of animals in ways not visible to the human eye.
Some noses are more of a puzzle than others. “Dogs are the exact opposite to reindeer,” said Prof Kroger. “Nobody knows why their noses are cold and why they have evolved that way. That is what we want to find out.”