Headline of the day! Amazing stuff! Don't be a deer in the dark!
So not only the smell of urine is important!
What is kind of odd is the article about the research mentions urine explicitly, while the abstract of the study does not mention urine at all. Were the scientists embarrassed? 😊
"When a male white-tailed deer walks through a forest in rutting season, it makes itself known. It tears off tree bark with its antlers and rubs its forehead glands on the tree. Then, it scrapes a hole in the ground and pees in it. The display asserts the buck’s dominance and advertises that he’s looking for a mate. Now, new research suggests that in the twilight hours when the deer are most active, these rubs and scrapes, known as signposts, glow in a bluish tinge other deer may see, scientists report this month in Ecology and Evolution. ...
The glow is an example of photoluminescence, a property widely found in nature in which organic material absorbs light and re-emits it at longer wavelengths—shifting ultraviolet (UV) light into our visible range, for example. Most research has focused on the photoluminescent properties of the animals themselves, but DeRose-Broeckert and his team wanted to see whether it also appeared in the environment.
In the Whitehall Forest in Georgia, he and his colleagues searched for wild white-tailed deer (Odocoileus virginianus) signposts during two periods leading up to the breeding season. They scanned signposted trees, the ground, and urine with UV light in two wavelengths thought to be relatively more abundant at dawn and dusk. Then they measured the light that came back, focusing in on wavelengths that would be picked up by receptors in deer eyes. In total, the team analyzed 146 signposts, including 20 urine patches.
The signposts—both rubbed trees and urine—lit up in a way that would pop out to deer in the dark, the team found. “The urine definitely glows, it looks like spilled white paint,” ... “It’s pretty striking.” To the deer, the trees and urine may appear as glowing patches of turquoise-blue, he says. ..."
From the abstract:
"Ultraviolet (UV) induced photoluminescence is widespread in Mammalia; however, its function(s) remain unclear. Most of the research to date has focused on the surface expression of photoluminescence (e.g., pelage), described qualitatively.
Here, we report a quantitative assessment of photoluminescence of white-tailed deer (Odocoileus virginianus, herein deer) used for marking signposts.
We analyzed 146 signposts, including 109 antler rubs on trees and 37 scent-marking scrapes. We compared the spectra of signposts to the spectra of surrounding environmental features elicited by exposure to excitation lights peaking at 365 and 395 nm.
Signposts showed significant contrast when compared to environmental backgrounds (p < 0.001), and the resulting photoluminescence would be visible to deer based on previously described deer visual capabilities.
This research is the first quantitative description of the functional use of environmental photoluminescence by a mammal and gives new perspective about how white-tailed deer perceive their environment and communicate."
White-tailed Deer Signpost Photoluminescence (open access)
Fig. 6 The average irradiance of white-tailed deer (Odocoileus virginianus) urine found at scrapes (N = 20) and surrounding forest floor when exposed to 365 nm ultraviolet (UV) light
