By Sean Hubbard, Communications Specialist, Agricultural Communications Services, Oklahoma State University
STILLWATER, Okla. – His name is Copper and he is a hound dog. An unforgettable scene from the early 80’s animated movie, The Fox and the Hound, shows Copper actively sniffing his surroundings in search of Todd, the movie’s co-star.
“Whatcha smellin’?” Todd asked. “I’m on the trail of something,” replied Copper.
“Trail of what?” Todd asked. “I don’t know, yet,” Copper said, pressing his nose right up against the fox, Todd. “Why, it’s you!”
The cartoon movie understood there was a connection between scent and predation and Oklahoma State University researchers have dug deeper into that poorly studied link. As a graduate student in OSU’s Department of Natural Resource Ecology and Management, Dillon Fogarty, advised by Scott Loss, NREM assistant professor, studied olfactory concealment, the way environmental features impact how a prey animal’s scent disperses and is detected by predators.
“Our research provides new information that changes the way people think about wildlife habitat. It is well known that scent plays a big role in predator and prey interactions, but how habitat influences scent dispersal and detection is not clear,” said Fogarty, who is now a doctoral student at the University of Nebraska. “Traditionally, people studied the visual concealment that wildlife habitat provides because people are visually oriented. We took the novel approach of putting ourselves in the animals’ shoes and investigating how vegetation and wind conditions provide olfactory concealment, which could be just as important as visual cover because many animals are heavily dependent on smell.”
Fogarty and Loss led the research in collaboration with NREM professors Dwayne Elmore Sam Fuhlendorf.
On Win and Kay Ingersoll’s ranch in Inola, Oklahoma, the research team took airflow readings at over 200 points in three vegetation communities – forests, shrublands and grasslands. They measured wind turbulence, velocity and updraft, along with visual habitat elements like vegetation height and density.
“Our objective was to predict where areas with olfactory concealment would be located,” Fogarty said. “We found that wind turbulence is an important aspect of olfactory concealment for predators and prey in grasslands. And interestingly, the best predictor of turbulence in grasslands was vegetation density, indicating that as vegetation density increases so does wind turbulence and that areas with high turbulence tend to also have high levels of visual concealment.”
Another novel finding from the study, which is published in the Ecological Society of America journal, Ecology, included an artificial nest experiment where the researchers covered farm-raised quail eggs with scent and placed them in grasslands on the Ingersoll’s ranch. The researchers returned the following day to see if a predator had removed the eggs.
“Surprisingly, we found turbulence intensity, not visual concealment, was the best predictor of egg persistence in grasslands. Nests in areas with high turbulence were less likely to be found by predators. This result provides the strongest evidence yet that habitat characteristics that enhance olfactory concealment actually impact survival rates of prey.
Fogarty says to understand how turbulence intensity provides olfactory concealment, think of a stream of red dye dropped into a river. If there is smooth streamflow the dye stays on a consistent and predictable path, but in turbulent rapids the dye disperses unpredictably, making it difficult to track upstream.
Based on the team’s research, Fogarty explains that “areas with high wind turbulence in grasslands function just like rapids, making it difficult for predators to track airborne prey scents back to their source.”
“The idea that areas with high visual concealment also provide good scent concealment is a major finding from our study,” Loss said “Researchers previously studying habitat may have wrongly assumed that the only benefit of tall and dense vegetation is visual cover. Our study shows that the same dense vegetation also provides olfactory cover by increasing wind turbulence. Additionally, our nest experiment shows that air turbulence is actually likely to be impacting predator detection and prey survival.”
Fogarty and Loss say that considering these separate aspects of concealment provides a better understanding of how prey hide their scent and how predators detect prey. Their findings reshape our understanding of wildlife habitat and even have implications for how we manage habitat for prey and predator wildlife species of conservation interest.
Fograty’s full paper, “Variation and Drivers of Airflow Patterns Associated with Olfactory Concealment and Habitat Selection,” is available online.
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