Researchers use wildlife cameras to study animal interaction and behavior in human-dominated landscapes
Burn out. It is a syndrome that is said to affect people who experience chronic stress. But after conducting a novel study with wildlife cameras showing the interactions between white-tailed deer fawns and predators, a researcher from Penn State suggests that prey animals can feel this too.
“And you can understand why they do that,” said Asia Murphy, who recently graduated with a PhD from Penn State University’s Intercollege Graduate Degree Program in Ecology. “Less than half of white-tailed fawns live by their first birthday, and many are killed by predators such as coyotes, black bears, and bobcats. Fawns instinctively ‘know’ that they are in constant danger. “
Ironically, the presence of humans – who do no harm to the fawns and would likely protect them if they could – only exacerbates the stress the kittens experience, Murphy added. Even if it’s just humans hiking a trail in a state park, it’s a disorder that fawns should avoid because they have less scenery and less time to feed and avoid predators.
“The presence of humans creates an environment where the danger seems so high that the animals basically stop being vigilant,” she said. “That was the surprising thing about my research – when fawns realize that so many dangers come from so many sources, their behavior seemed like they had just relaxed, like there was no point in hiding or fleeing. I’ve seen that with older deer too. “
In areas where there are lots of predators and humans, the fawns seem to relax rather than behave hyper-vigilant, she noted.
“Being so much constant stress makes you burned out,” she said.
The aim of the study was to investigate how human-dominated landscapes affect the timing, frequency and physical distance and locations of interactions between humans, black bears, coyotes, bobcats and fawns, as well as to compare the vigilance behavior of the deer in each location . The researchers compared “camera trap” data from six surveys in and around three public forest locations in central Pennsylvania with different environments – forest, agriculture, and development.
The Bald Eagle and Rothrock State Forest sites were surrounded by low density agriculture and housing, while the Susquehannock State Forest site was surrounded by largely uninterrupted forest. When analyzing more than 10,000 photos, the researchers observed significantly different behavior of fawns, adult deer and predators at the three locations, dictated by the presence of humans and their changes in the landscape.
Camera trap investigations began in mid to late May, which coincided with the start of the time fawns are born and are most susceptible to predators, and ended in mid-September before the hunting season. The researchers randomly selected 18 camera locations at each of the three study sites, at least half a mile apart within an area of approximately 100 square miles.
At least one camera was placed at each location and typically stayed there for an average of 47 days before being relocated. Cameras have been set to take three pictures when triggered by an animal with a one-minute rest period. Each location was baited with a combination of bobcat urine, a skunk-based fragrance, and a fatty acid tablet.
In the results recently published in Journal of Animal Ecology, the researchers reported that bears, bobcats, coyotes, fawns, and adult deer had more overlaps in time in the agricultural and development sites than in the largely uninterrupted forest area. In addition, factors influencing deer vigilance, such as the distance to the edge of the forest and the frequency of predators in the agricultural and development sites, were not factors in the largely uninterrupted forest area.
“By considering the different antipradator behaviors that can be detected and the different magnitudes that those behaviors can occur, we have been able to gain a broader picture of how humans are reducing the niche space available for wildlife,” Murphy said. “It was clear that disturbed landscapes – agriculture and development – create more time and space overlaps between predators and fawns.”
This research is important because it was among the first to document that human land disturbances affect the dynamics of predator-prey interactions, according to Murphy’s advisor Duane Diefenbach, associate professor of wildlife ecology at the College of Agricultural Sciences. Wildlife biologists suspected that human interference increased the chances of predators, but they hadn’t seen any evidence.
“This study shows that fawn antipradator behavior varies by space, time, and predator species,” said Diefenbach, director of the Pennsylvania Cooperative Fish and Wildlife Research Unit for the US Geological Survey in Penn State. “If several predatory animal species occur at the same time, but differ in their use of space, duration of activity and type of hunting, a complex landscape arises for prey animals that try to avoid predation. The presence of humans has the potential to change the interactions between predators and prey and where and when encounters take place. “
Also involved in the research were David Miller, Associate Professor of Wildlife Population Ecology, Penn State, and Pennsylvania Game Commission biologists Mark Ternent and Matt Lovallo.
The Pennsylvania Game Commission funded and supported this research.