How the blue light of the Arctic winter helps reindeer distinguish predators and food
Reindeer have an extraordinary biological feature. Scientists discovered in 2013 that The eyes of reindeer change shade and color according to the seasons., reflecting the colors of the Arctic sky. If you look into the eyes of the Arctic reindeer (Rangifer tarandus) during the summer, when the days are long and the sun shines, you will notice a gold and turquoise glitter, similar to the emerald reflection of a cat's eyes at night. But when winter comes and darkness prevails, the deer's eye turns blueThis is a natural metamorphosis, a unique adaptation that, according to scientists, may function as biological sunglasses for deer.
Reindeer feed at dusk, and during the Arctic winter, twilight can last for more than a third of the day, creating a strong blue light that reflects off the icy landscape. To see better dire wolves and nutrient lichens in the semi-darkness, their eyes reflect more blue light during the winterThis gives the weak light an extra pass through the retina, allowing the photoreceptors to gather more information. In this way, the deer gain a better view. up to 1.000 times brighter at dusk, but with a significantly lower resolution, as if looking through a fogged window.
Like many other mammals, deer have a light-reflecting layer in their eyes, which is located behind the retina and is called the tapestry of light. However, no other known mammal has a tapetum like that of the reindeer, Telegrafi reports.
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In a 2022 article for The Conversation, ophthalmologist Robert Fosbery compared this natural change to regulating tire pressure. In cold conditions, a little air is released from tires to increase grip on ice. Similarly, deer “release” fluid from the tapetum of the eye to improve vision in the surrounding environment. The exact mechanisms of this structural change are not yet fully understood, but researchers believe that are related to the fluids inside the eye.
In 2022, scientists compared the eyes of deer that had died in the summer with those that had died in the winter. Their findings support the idea that persistent pupil dilation in dim light affects the balance of eye fluids, causing structural changes in the tapetum. Unfortunately, the researchers were unable to compare the tapetum of the same individual in both seasons, so it remains unclear what exactly drives this seasonal change. To solve this mystery, deer eyes can be studied in autumn and spring, to see how they gradually transition from summer to winter shades.
At the moment, it is known for certain that The eyes of the arctic reindeer are truly unique.Who knows, maybe some other mammals that live in low light conditions develop similar adaptations to adapt to the dark world that surrounds them... /Telegraph/
