Deer have the ability to see in ultraviolet light, and recent research has shown that they can leave behind glowing trails that are visible even at those wavelengths.

This discovery shed entirely new light on how deer communicate with each other and how they perceive their environment.

Male white-tailed deer (Odocoileus virginianus) are known to leave footprints in the forest during the autumn breeding season. They rub their horns against trees and the forest floor, shed the velvet on their horns (the soft, blood-rich velveteen “skin” that covers the horns that calcify as they grow), and leave scent trails in the form of glandular secretions, urine, and poop.

These marks, known as “deer scrapes” (on trees and shrubs) and scent scrapes (on the ground), act as beacons that alert other animals to the deer’s presence. That is, a warning to a rival, a catcall to a mate.

However, it seems that scent is not the only language deer use to communicate.

Scientists at the University of Georgia (UGA) in the US have discovered that these marks “glow” at ultraviolet wavelengths. previous research deer eyes can see.

“The resulting photoluminescence would also be visible to deer based on their aforementioned visual abilities,” the research team said. I will write In a published paper describing this phenomenon.

This is the first time scientists have documented evidence of a mammal actually using photoluminescence in its environment. UV-induced photoluminescence in mammals It has been studied for over a century.

Furthermore, in the learning check, Most of the boxes you need To determine whether photoluminescence actually serves a biological function.

Daniel DeRose-Broeckert (UGA Graduate Research Assistant) and colleagues The study was conducted on 337 hectares (approximately 840 acres). Research forest called White HoleA place where deer roam freely.

The research team tracked the deer’s “signposts” (109 scrapes and 37 abrasions) during two month-long surveys in the fall of 2024, returning to each site at night using ultraviolet flashlights with peak wavelengths of 365 nm and 395 nm.

Both of these wavelengths are abundant in the sky at dusk and dawn, when deer are most active. Previous research has also shown that deer can see reflections and emissions of these wavelengths, so anything that shines bright enough under these torches will be easily visible to deer.

The scientists instead used a tool that measures irradiance values, or how much light is reflected or emitted at each wavelength from a particular spot.

“Scrubs and urine exposed to 395nm and 365nm exhibited photoluminescence with higher average irradiance values ​​(i.e., brighter) than the surrounding environment,” the researchers said. report.

It’s unclear how much of this glow comes from trees and shrubs and how much comes from leftover deer body fluids. For example, deer urine contains porphyrins and amino acids that are excited at longer UV wavelengths. Phenols and terpenes released from the forehead glands of male deer are thought to have similar properties.

Deer damage to plants exposes woody lignin and plant terpenes, and these compounds are also known to exhibit photoluminescence.

“Whether the photoluminescence is the result of the deer’s forehead gland secretions or the properties of the wood, the fact remains that friction visually contrasts the surrounding environment in a way that is unique to deer vision,” the researchers said. memo.

Related: American bats can glow a ghostly green color, and scientists don’t know why

Under both types of UV flashlights, the photoluminescence emitted by deer signposts was of the type suitable for registration. Due to cones in deer eyes that are sensitive to short and medium wavelength visible light.. Scientists say this reaffirms that deer vision is adapted to their environment. low light conditions of dawn and dusk.

What’s even more impressive is that deer communicate using illuminated “bulletin boards” scattered throughout the forest. This bulletin board is not visible to other people.

aWhat is the deer saying? We won’t know for sure until more research is done.

“Although we did not directly test for changes in deer behavior due to the presence of photoluminescence, it is known that as deer hormone levels increase, friction irradiance also increases, and behavioral changes occur as the breeding season progresses,” the researchers said. I will write.

This study ecology and evolution.