Reindeer
Sunlight drives seasonal changes in the Arctic! Reindeer may be best known for fictional Rudolph's glowing red nose, but now scientists find the animals can alter their eye color as well. The backs of their eyeballs change from gold in the summer to blue in the winter. This change in color helps reindeer eyes capture more light during the dark winter months in the Arctic.

Photo: Division of Natural Resources, Gov't of the NW Territories