Glowing urine and shining bark: Scientists discover the secret visual language of deer

During mating season, when male white-tailed deer want to get noticed by the opposite sex and warn off rivals, they rub their antlers against trees and scrape the forest floor. Then they pee on these patches. But there is more to these physical and scent markers than meets the eye—or nose. According to a new study published in the journal Ecology and Evolution, they also glow so that other deer can see them when it's dark.