Sunday, December 7, 2014

Penn State Study Revealing How Deer React To Hunters

Deer “know” when hunting season starts and react accordingly, disappearing into nooks and crannies of the landscape where they become almost invisible.

Every hunter has heard that tale. It turns out there's truth to it.

Researchers from Penn State's College of Agricultural Sciences are entering Year 2 of a five-year deer and forest study. It's being carried out on four sites, each measuring 25 to 40 square miles, in Bald Eagle, Rothrock and Susquehannock state forests.

The study has several goals, including:

• Examining deer impacts on forest health and the effectiveness of the measures to monitor it.

• Determining how hunters use the deer management assistance program and how they react to changes in the deer population.

But something else is proving interesting.

As part of their work, researchers have put collars on deer — including bucks that have survived two hunting seasons — and tracked their movements. GPS collars transmit data about deer locations. That occurs every five to six hours in winter, spring and summer and every three hours during archery season. It increases to every 20 minutes during the two-week firearms gun season.

Information collected thus far shows deer react — and not in a small way — to the orange army of hunters nearly 800,000 strong each gun season.

“Their behaviors in archery season, there's nothing to suggest these deer are being impacted by the hunting that's going on to any great extent,” said Duane Diefenbach, leader of the Pennsylvania Cooperative Fish and Wildlife Research Unit, and one of the study's leaders. “But once the rifle season begins, we see some pretty dramatic differences. Some of these bucks will leave their home range and go places we've never seen them in the previous 10 months. It's pretty amazing.”

Equally so is how sensitive those collared whitetails are to pressure, Diefenbach said. They change their patterns almost immediately on the Sunday before the opening day of deer season — when hunters enter the woods to check on their stands, make a last scouting trip or burn off the energy of anticipation — and then go back to their normal routine within a day of the season ending, he said.

“It's like flipping a switch,” Diefenbach said.

And where do all those savvy bucks and does go?

Wherever hunters can't, don't or won't, said Chris Rosenberry, head of the deer and elk section for the Pennsylvania Game Commission and a biologist involved in the study.

He cited the example of one savvy buck. It climbed about 400 feet higher in elevation once hunting season started than it had before and moved further into the woods, so it was about 1,000 yards from the nearest road.

That kind of reaction was typical of deer that survived the season, he said.

“These animals were in areas that are not readily accessible. They went beyond where the hunters were,” Rosenberry said.

It's not true that they become largely nocturnal, Diefenbach said. That commonly held notion appears to be “a lot of bunk,” he said.

Rather, Rosenberry said, deer retreat to places hunters aren't.

“Every one of these animals, if they survive two hunting seasons, have places that either no one goes or that are just so thick. Unless you did a drive, they're just going to walk circles around you,” he said.

Diefenbach said he hopes to send people to walk the ground where these deer hide to see what those spots look like.

In the meantime, the deer are making good use of them. Hunters killed only about 10 percent of collared does and 20 to 25 percent of collared bucks in Year 1 of the study, Diefenbach said.

That so many deer survived is not surprising, at least when it comes to does, Rosenberry said. Multiple studies have shown 85 to 90 percent of does survive hunting season no matter how long the season.

The low buck harvest rate was a little more unexpected, he said. But, he added, as the study is revealing, perhaps they shouldn't be.

“The odds are stacked against the hunter,” Rosenberry said. “These deer are not nearly as predictable as hunters would like them to be.”

Deer and forest health

Ten years ago, if you had asked Duane Diefenbach about the main limiting factor to the lack of forest regeneration, his unequivocal answer would have been white-tailed deer, he said.

Now he's not so sure.

“We've reduced deer numbers. The question now is do we really need to reduce deer numbers more? Or is there some other factor that we need to consider?” the Penn State researcher said.

Specifically, how is overbrowsing by deer coupled with soil conditions, lack of sunlight reaching the forest floor, competing vegetation — from species like ferns and rhododendron — and other factors combining to impact what the forests of tomorrow will look like?

The deer-forest study conducted by Penn State in cooperation with the Pennsylvania Game Commission and Pennsylvania bureau of forestry could offer answers.

Researchers erected new deer exclosures — 20-square-foot areas fenced to keep deer out — representative of the surrounding landscape at various points in four study areas. The plan is to monitor them over time to document what species grow within their confines, in what abundance and how well and quickly, then compare that to what's outside the fence, where deer can browse, Chris Rosenberry of the Game Commission said.

The commission's current deer management program is based, in part, on deer impacts on forest health, he said. That's determined using measures provided by the U.S. Forest Service.

This study might offer insight into how sensitive those measures are and whether they could be made better, he added.

Researchers also want to hear from hunters. They want to know how they're hunting on study areas, whether and how they're using the deer management assistance program and how they rate their hunting experiences.

Hunters interested in getting involved can visit or call 877-778-3637.
“We can control how many deer we catch and how many collars we put out. The one thing we have no control over is hunter cooperation,” Rosenberry said. “It's critical they register and provide that information.”
— Bob Frye

Bob Frye is a staff writer for Trib Total Media. Reach him at or via Twitter @bobfryeoutdoors.

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