While Santa’s sleigh has always been pulled by reindeer, it wasn’t until 1939 that Rudolph the Red-Nosed Reindeer joined the team. But while Rudolph’s bright red nose has always thought to be unique, it’s recently been discovered that he is not alone.

That’s because a group of European researchers have found something unusual about the species of reindeer known as ‘Rangifer tarandus’. After extensively studying the species, they found that the colour is owed to the density of blood vessels packed into the noses of these reindeer, to help them regulate body temperature in extreme environments – like travelling at lightning speed through the cold winter’s sky on December 24th.

The scientists made the discovery by looking closely at the noses of two reindeer and five human subjects, who held a special microscope that allowed them to see individual blood vessels and the flow of blood in real time. After comparing the videos, they discovered that the reindeer had 25% higher concentration of blood vessels in their noses.

They also made the reindeer run on a treadmill, and looked at which parts of their bodies lost the most heat afterwards, using infrared imaging. The scientists found that the nose, along with the hind legs, reached up to 75° Fahrenheit. Because this is an extremely high temperature for a reindeer, they deduced that the function of all the blood flow was to help regulate temperature, bringing large volumes of blood close to the surface when the animals are overheated, so its heat can radiate out into the air.

“These results highlight the intrinsic physiological properties of Rudolph’s legendary luminous red nose,” the study’s authors said. “They help to protect it from freezing during sleigh rides and to regulate the temperature of the reindeer’s brain, factors essential for flying reindeer pulling Santa Claus’s sleigh under extreme temperatures.”

So now, as well as being able to say that Rudolph’s nose glows, you can even say why!