Deer markings actually glow

The scrapes and rubs the mammals leave behind shine under UV light humans can't see. Breakthroughs, discoveries, and DIY tips sent six days a week. Animals see the world around them in ways that we humans can only imagine. Arctic reindeer's eyes change color with the season to help them find food, while giant squid have eyes the size of dinner plates. Many species take advantage of seeing ultraviolet (UV) light that's invisible to humans--including deer .