Constant danger leaves deer fawns in a state of burnout

In a new study from Penn State, researchers have used trail cameras to study interactions between white-tailed deer fawns and their predators in human-dominated landscapes. The investigation revealed that when fawns feel that they are constantly in danger, they seem to relax instead of trying to head for cover. 

The experts compare this phenomenon to the effects of “burnout” in humans who endure chronic stress. The results of the study suggest that prey animals experience their own version of burnout.

“And you can understand why they do,” said study lead author Asia Murphy, who recently graduated with a doctorate from Penn State’s Intercollege Graduate Degree Program in Ecology. 

“Less than half of whitetail fawns live to see their first birthday, and many are killed by predators, such as coyotes, black bears and bobcats. Fawns instinctively ‘know’ they are in constant danger.”

Ironically, said Murphy, the presence of humans – who would protect the fawns if they could – only ratchets up the stress the young animals experience. The fawns instinctively avoid areas with people, which further limits the part of the landscape they can use to feed and evade predators.

“The presence of people creates an environment where the danger seems so high that the animals basically stop having vigilance behaviors,” said Murphy. “That was the surprising thing about my research – when fawns perceive that there is so much danger coming from so many sources, their behavior seemed like they just relaxed, like there’s no point in being ready to hide or flee. I saw that in older deer, too.”

Murphy noted that in areas where there are many predators and people present, fawns seem to relax instead of acting hypervigilant. “Like so much constant stress leaves them burned out.”

The research was designed to investigate how human-dominated landscapes influence interactions between humans, black bears, coyotes, bobcats and fawns. The researchers compared camera trap data from surveys in six forested sites across Pennsylvania. The sites had different surroundings, including forest, agriculture, and developed areas.

The researchers found that bears, bobcats, coyotes, fawns, and adult deer all had more frequent overlaps in the agriculture and development sites compared to the mostly unbroken forest site. 

“By taking into account the different antipredator behaviors that can be detected and the different scales at which these behaviors might occur, we were able to gain a more comprehensive picture of how humans reduce available niche space for wildlife,” said Murphy. 

“It was clear that disturbed landscapes – agriculture and development – create more time and space overlap between predators and fawns.”

The study is published in the Journal of Animal Ecology.

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By Chrissy Sexton, Earth.com Staff Writer