Scientists cannot resist anomalous phenomena, so it should come as no surprise that they have long followed the once-yearly travels of a most unusual reindeer, a famous specimen of the arctic species Rangifer tarandus tarandus. This individual, who is widely known as “Rudolph,” displays a particularly conspicuous morphological adaptation.

Rudolph exhibits a vibrant red—some may even refer to it as shiny or glowing—proboscis. While the benefits of this adaptation have yet to be fully measured, members of the scientific community are already speculating that it is indeed an advantageous evolutionary step.

One scientist in particular, Nathaniel J. Dominy, Ph.D., a professor of anthropology and an adjunct professor of biology at Dartmouth, is sharing his knowledge as enthusiastically as young scientists fill out their requisition forms. As of December 21, Dr. Dominy’s findings have been available in an article (“Reindeer vision explains the benefits of a glowing nose”) posted by Frontiers for Young Minds.

According to Dr. Dominy, arctic reindeer already have a number of interesting traits that provide advantages for survival during the dark and cold winter months. Unlike most other mammals, including humans, the reindeer has the ability to see into the ultraviolet (UV) light spectrum. The ability makes them better able to discern from their surroundings the presence of white-furred predators like wolves, as well as more clearly spot certain kinds plant matter, such as lichens.

Lichens are essential to the reindeers’ survival, one of its primary food sources until summer’s thaw, so its darker appearance to reindeers' eyes make it stand out against the UV-reflecting snow, especially in the midwinter months when the ambient light is itself primarily purple to ultraviolet. In this environment, the introduction of a luminescent red nose may further increase the ability to spot predators and food sources.

The animals’ optical anatomy has also evolved to increase the unusual visual range’s efficacy. Like many animals—both wild and domesticated—reindeer eyes contain a special reflective tissue that causes the “eye shine” you may see, for example, when a deer spots a car coming toward it at night or when you take a photo of a pet cat. This tissue is called the tapetum lucidum.

In reindeer, the tapetum lucidum remarkably changes color based on the time of year. The gold eyes of summer change to a cold blue as the days shorten and night takes a stronger hold on the North. While the precise advantages of this transition are unknown, some speculate that it could result in enhanced vision in the blue range. To the contrary, some believe that this would actually act as a disadvantage when faced with foggy conditions, something of particular concern this year as we experience the effects of El Niño.

El Niño patterns create cooler, drier meteorological conditions throughout northern latitudes and unusual levels of humidity throughout the more equatorial regions—including an increased incidence of fog, which effectively scatters light beyond useful visibility. Certain colors are more detectable through water than others, and red is the most likely to penetrate a dense fog. This is where the individual, Rudolph, has a leg up on his reindeer peers. Whereas others of the species will have marked impairment in fog, the red nasal illumination would ensure this individual superior vision in moisture-heavy atmospheric conditions.

There are some possible disadvantages to sporting a red, illuminated nose. Until closer examination becomes possible, some anatomists can only speculate that the red nose is indicative of increased presence of capillaries close to the skin’s surface. The possibility of abnormal red coloration due to infection has been dismissed until more evidence comes to light.

Reindeer have complex circulatory systems, and the nose in particular becomes important in terms of thermoregulation. If there is too much exposure to subzero temperatures, Rudolph may be at greater risk for hypothermia than his brown-nosed peers. “It is therefore imperative for children to provide high-calorie foods to help Rudolph replenish his energetic reserves, says Dr. Dominy.

Although a red nose such as Rudolph’s may have its drawbacks, it does seem a beneficial adaptation on the whole. Whether this adaptation will become more common, however, is unclear.

“Currently, we know of only one luminescent nose in the reindeer population, but its advantages suggest that it could be passed on to future generations of reindeer,” wrote Dr. Dominy. “On the other hand, the frequency of foggy weather is decreasing worldwide due to climate changes, which may make the benefits of a glowing red nose less important in the future.”

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