Reindeer change their eye colour with the seasons to help them to see in the gloomy Arctic winter.
Their eyes turn slowly from gold in the summer to blue in the winter, according to scientists at University College London (UCL).
Glen Jeffery, a neuroscientist who led the research, said: “No one’s seen this before. The Sami people, who are the herders, only really see their animals one time a year.”
The finding suggests that reindeer, which migrated to the Arctic 10,000 years ago, have adapted to winter’s blue-tinged darkness above the Arctic Circle.
Professor Jeffery began the research ten years ago after Norwegian colleagues sent him two bags of reindeer eyes of different colours — one from an abattoir taken in the winter and one