Depending on when you see them, the eyes of an arctic reindeer will change in color. In the summer, they're almost golden. In the winter, they seem deep blue. This is not due to a change in their mood or even a reaction to the temperature, but rather because of a change in the amount of overall light in the environment.
More facts about arctic reindeer:
- Researchers think these changes in eye color are unique to arctic reindeer. Other critters whose eyes have a tapetum lucidum, such as horses and house cats, don't exhibit this seasonal shift.
- Arctic reindeer can see in low light conditions, and although that world is not in focus, it is usually sufficient for them to recognize a predator on the prowl.
- Researchers also found a herd with green eyes living near a Norwegian university, where community lighting keeps their habitat dimly lit.