Why reindeer eyes turn deep blue in winter and how it helps them see in Arctic twilight
Reindeer experience a seasonal change in eye color that enhances their ability to see in dim Arctic light. This adaptation involves a shift in the tapetum lucidum from gold-turquoise in summer to deep blue in winter. The deep blue reflection helps reindeer forage and detect predators in low-light conditions. Changes in collagen fibril spacing within the eye's reflector contribute to this transformation.
