Much like how we swap out our shorts and sandals for long trousers and boots come winter time, many animals trade in their pelts for a warmer model, or do avoid being seen by their prey (or predators). Reindeer take this one step further. They change the colour of their eyes…

Turns out that reindeer don’t need colour contacts, just a change of season for a whole new look. In summer they have light, golden eyes to help them mange the near constant daylight. Come wintertime their eyes darken to blue to help with the near constant darkness.

And yes, those Arctic foxes are filthy hypocrites. Though they have their own problems.

If you want to get into the nitty gritty of it all (and the physics of the reflection of light) check out the original research article here: Shifting mirrors: adaptive changes in retinal reflections to winter darkness in Arctic reindeer.

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Tanya Strydom is a PhD student at the Université de Montréal, mostly focusing on how we can use machine learning and artificial intelligence in ecology. Current research interests include (but are not limited to) predicting ecological networks, the role species traits and scale in ecological networks, general computer (and maths) geekiness, and a (seemingly) ever growing list of side projects. Tweets (sometimes related to actual science) can be found @TanyaS_08.