Reindeer Eyes Change with the Season

Reindeer live in the Arctic, where summers are bright and winters are very dark. To help them see in these different light conditions, reindeer eyes change color. In the summer, their eyes are golden-yellow, and in the winter, they turn deep blue. This change helps them see better during the long, dark Arctic winters. 

The Role of the Tapetum Lucidum

This color change happens in a part of the eye called the tapetum lucidum, a reflective layer behind the retina. In summer, the golden tapetum reflects most light back through the retina, which is suitable for bright conditions. In winter, the tapetum turns blue, scattering more light through the photoreceptors and increasing the eye’s sensitivity in low-light environments. 

Unique Design

This is the first time such a color change has been observed in mammals. It shows how reindeer are specially designed to survive in their extreme environment. The blue reflection from the winter eye likely favors ultraviolet sensitivity, which is abundant in Arctic light but invisible to humans. Reindeer use this to find food and see predators. 

Sources

• ScienceDaily: “Bright eyes: Reindeers’ eyes change from blue to gold with Arctic seasons” 

• National Geographic: “What color are reindeer eyes? Depends on the season.” 

• Smithsonian Magazine: “Reindeer Eyes Change Color to Match the Season”