Have you ever thought about how Rudolph keeps his cool? I mean he spends an entire day and night flying from roof top, to roof top all the way around the world, with the ever-so-slim Santa (no offense Mr. Claus), millions of toys, for all the girls and boys, and that pretty nifty magical sleigh. It is winter, and pretty cold, but he must be cooking under that thick insulated fur jacket of his. It is quite amazing that he doesn’t overheat, working so hard every Christmas Eve. How can he do it? Well, as it turns out I am not the only one who is pondering the magic of Rudolphs thermal regulation, Arnoldus Blix from the University of Tromso, in Norway was curious as well, and he took action.
Blix gathered two of his colleagues, Lars Folkow, also from Tromso, and Lars Walloe, from the Univeristy of Oslo, and began to train the reindeer to run on treadmills. “Reindeer are the best animals to work with; once they trust the trainer they will do anything for you,” stated Blix. So, the reindeers started out on a trot. They were going about 9km/h in a room that was about 10 to 30°C. As they were warming up their respiration rate spiked going from 7 breaths/min to 260 breaths/min. This was their first strategy of cooling off; panting with their mouths closed. With this high rate of respiration, the animals are breathing in the cool air, which is in turn evaporating water from the mucous membranes in their noses. This evaporation cools their blood in the nasal sinuses and is then transmitted back to the rest of the body, cooling them down.This form of cooling only lasts so long though.
With increased exercise, more heat is being generated under their thick coat causing them to alter thier strategy in an attempt to get more cool air in. This is where they open they mouths and being panting like a dog. This second trait is working with evaporation, just like the previous one, except it is evaporating water off their tongues. With high circulation in the tongue this leads to a more efficient way of cooling themselves down as they can now send more cool blood back into thier bodies.
Bix and his colleagues kept running the reindeer until they realized a very interesting temperature change occurring in the reindeer’s brain when it hit a high of 39°C. The reindeer began to divert the cooled off blood from their nose away from the body, up to the brain. They were selectively cooling the blood to their brain! This seemed not logical to Blix as, “only 2% of the respiratory volume went through the nose when they resorted to open mouth panting.” But because they do reside in such cold temperatures, up in the Arctic, this was just enough to keep their brains cool and functional.
So, there you have it, Rudolph and the other six reindeer pulling Santa’s sleigh, have three different traits to cool themselves off as they are vigorously flying through the air; panting through their nose, flapping their tongue around in hope of more evaporation and selectively cooling their brain!
