Reindeer are famous for pulling Santa’s sleigh, but there’s a characteristic that sets them apart

Reindeer are renowned for their role in pulling Santa’s sleigh, but what truly distinguishes them is their remarkable vision. While Rudolph the red-nosed reindeer may enjoy a bounty of carrots on Christmas Eve, researchers from Dartmouth College in New Hampshire and the University of St. Andrews in Scotland have uncovered an intriguing aspect of reindeer vision that operates year-round.

Surviving in a frigid and desolate environment presents significant challenges when it comes to finding sustenance. However, these researchers suggest that reindeer eyes have evolved to excel at identifying their preferred meals. This revelation sheds light on the fact that, beyond their festive fame, it is their visual system that truly sets reindeer apart from other animals.

Nathaniel Dominy, a Dartmouth anthropology professor and co-author of a recent study published in the journal i-Perception, emphasizes the unique nature of reindeer vision. He notes that despite being relatively overlooked in the realm of visual neuroscience, reindeer possess a captivating visual system deserving of attention.

One longstanding observation has been the color-changing mirror-like tissue in reindeer eyes. It transitions from a greenish gold hue in the summer to a vivid blue in the winter, a transformation believed to enhance their vision in the low-light conditions of polar winters. However, what puzzled scientists was the fact that reindeer, unlike most mammals, can perceive light in the ultraviolet spectrum.

The typical response among daylight-active animals is to avoid UV light, as it can be harmful. Snow, abundant in the reindeer’s habitat, reflects UV light, which can cause snow blindness in humans. Researchers propose two potential explanations for this unique adaptation in reindeer vision: predator avoidance and food detection.

In terms of predator avoidance, the ability to spot white wolves against a snowy landscape could be crucial for reindeer’s survival. However, the recent study leans toward the food detection hypothesis. Reindeer primarily subsist on light-colored reindeer moss, which is, in fact, a type of lichen that grows in carpet-like patches across northern latitudes.

To investigate this further, researchers ventured to the Cairngorms mountains in the Scottish Highlands, home to over 1,500 species of lichen and Britain’s sole reindeer herd. They discovered that reindeer moss absorbs UV light. Consequently, the white lichen, which is difficult for humans to discern against the snow, appears as dark patches to reindeer.

In practical terms, this means that reindeer can more easily spot their preferred food source. By doing so, they conserve energy and increase their chances of survival. Nathaniel Dominy emphasizes the importance of this discovery, especially for these animals in their constant search for sustenance.

Juan Jose Negro, a specialist in evolutionary ecology and conservation biology, finds this research intriguing, although his primary focus is on birds of prey. While there may not be immediate biomedical applications, understanding how animals adapt to challenging environments is valuable. In the case of reindeer, their ability to see UV light might indicate a mechanism to protect their eyes from damage.

Reindeer eyes are rich in ascorbic acid, or vitamin C, which is known for its cell-repairing properties. This suggests a potential connection between their vision adaptation and cellular protection. As a result, the advice offered by Dominy, who previously explored why Rudolph’s red nose is ideal for guiding Santa’s sleigh, has evolved. Instead of leaving high-calorie treats for reindeer to combat nose-related heat loss, he now recommends focusing on their eyes’ health. Providing them with vitamin C-rich offerings like orange juice or carrots would be a thoughtful choice on Christmas Eve.