3 min readHere’s what you’ll learn when you read this story:
- The white-tailed deer (Odocoileus virginianus) uses the surprising language of UV light to communicate during breeding season.
- A new study found that male deer will rub their antlers or urinate on trees, creating a spectra of “signposts”—and these markings are photoluminescent.
- Because deer have eyes that are extra-sensitive to blue light, they can see this UV markings, creating a “communication hub” of sight and smell.
While the universe is an immensely large place, human vision can only see a small sliver of it. Because our red, green, and blue-coded cones can only detect light in the wavelenght range of approximately 380 to 750-nanometers, we can only see in what’s known as the “visible spectrum.” Of course, this is a somewhat species-ist term, because not all animals consider the same part of the spectrum ‘visible.’
Take, for example, your run-of-the-mill white-tailed deer (Odocoileus virginianus). These crepuscular (most active in the twilight hours) mammals have evolved cones that are extra sensitive to blue light. In fact, their eyes are so sensitive that their visual range dips into the ultraviolet (UV) part of the electromagnetic spectrum, meaning that they can see wavelengths of light that are completely invisible to us.
To understand how deer use this to their advantage, a team of scientists at the University of Georgia (UGA) explored how UV light might play a starring role in deer mating. The team analyzed 146 “signposts”—109 antler rubs and 37 urine-marked scrapes—across an 800-acre tract of land. When observing these signposts with UV light, the team discovered that they glowed via photoluminescence, likely attracting other deer to that spot. The results of the study were published in the journal Ecology and Evolution.
“In the process of scraping the bark off a tree with their antlers, they are depositing glandular secretions. Likewise, when they make a scrape, a different gland is also between their toes,” Gino D’Angelo, a co-author of the study from UGA, said in a press statement. “Deer have lots of ways to interact with the environment, and they are leaving those signatures out there to smell and glow.”
The animal kingdom has many neat tricks for creating light to communicate or attract prey. One of the most stunning examples comes from the deep sea, where bioluminescent fish (such as the anglerfish) use chemicals or bacteria in their bodies to produce light. Photoluminescence, on the other hand, requires an external UV light source to strike a material, which then lengthens and reflects that wave of light, pushing it into the visible spectrum.
With the antler rub markings, the scientists hypothesize that this photoluminescence originates from secretions of the deer’s forehead glands mixing with the tree’s sap. The other 37 scrapes likely get their UV glow from the deer’s urine.
“People have been hypothesizing about if this glow exists in the environment, but nobody had gone out yet to try and connect it to the deer until now,” Daniel DeRose-Broeckert, a graduate research associate at UGA’s Deer Lab and co-author of the study, said in a press statement. “Their vision is vastly different from ours. Once the Sun is slightly gone around dusk and dawn, the UV light dominates for deer since it’s not being washed out by the visible light spectrum from the Sun.”
These markings aren’t only a feast tailor-made for a deer’s eyes—smell also plays a powerful role, and both sensory cues likely communicate individuals’ breeding status and level of fitness to potential mates. And all of it goes unseen by our impressive (yet limited) human senses.
Best-Selling Products We Recommend
Darren lives in Portland, has a cat, and writes/edits about sci-fi and how our world works. You can find his previous stuff at Gizmodo and Paste if you look hard enough.