Reindeer Eyes Change Color

photo by Cappan/ iStock

I've added this one to my 'Things I Did Not Know' file:

Reindeer eyes change color depending on the time of year, which helps them see better in different light levels. Their blue eyes are approximately 1,000 times more sensitive to light than their golden counterparts, a crucial adaptation in the dark days of winter. Only one part changes color, however: the tapetum lucidum, a mirrored layer situated behind the retina. Cats have it, too — it's why their eyes appear to glow in the dark. This part of the reindeer retina shines a different hue depending on the season. 

Read more: Interesting Facts