September 22, 2010
Duane Diefenbach is a deer hunter himself, so he is uncomfortable that some may interpret the results of his three-year, ground-breaking hunter-movement research as reflecting badly on sportsmen. But, says the adjunct assistant professor of wildlife in Penn State's College of Agricultural Sciences, "We learned what we learned."
And it is not as though the information generated by the study -- done by the Human Dimensions Unit of the School of Forest Resources -- is imprecise. Far from it, in fact. Many deer hunters in a 180-square-mile area of Sproul State Forest in Clinton County during the first week of the 2001 and 2002 rifle seasons carried GPS (global positioning system) units. Meanwhile, researchers periodically flew over the area, plotting the locations of hunters on topographic maps. Participants in the research were debriefed in detail about their perceived movements and hunting locations.
"No one has ever studied hunter movement before with this kind of technology," Diefenbach says. "We didn't know what to expect. There are a lot of perceptions out there. As uncomfortable as the answers may be, the research is needed for better deer management, and we need to know what is going on with hunters. There is a lot of research available that was done by asking hunters where they go and how they hunt, and a lot of opinions. But there are few hard facts about what actually happens on the ground."
From all those data, researchers built predictive models of hunter movements and analyzed them in relation to proximity of roads, commonality of terrain and coverage of habitat. The discomfort Diefenbach refers to comes from sportsmen who might not believe his conclusion. In the study area, during the study years hunting pressure was extremely light, and few hunters walked very far or ventured onto the steeper slopes.
"Hunters were bunched in flat areas within a third of a mile of the roads," the researcher says. "After the first day of the season, once you got more than a third of a mile from a road, the hunter density dropped to about one hunter for every eight square miles. The highest hunter density we saw was on a first day, and it was only about 1.75 hunters per square mile."
What his research shows, Diefenbach believes, is that on the "big woods" tracts in the northcentral region of the state, hunting pressure on public lands is extremely low. "It's evidence that public lands do not have the excessive hunting pressure that many believe," he explains. "The conventional wisdom is that public lands have high hunting pressure and an overharvest of deer.
"That may be true in some areas, but certainly not in the region we studied," he points out. "After the first days of the seasons, we had difficulty just finding hunters to carry our GPS units for the research. We believe this situation exists across the northcentral region."
Incorporating GPS technology gives the research more credibility, believes Rich Stedman, assistant professor of rural sociology, who helped design the study. "We distributed more than 300 GPS units during the research," he says. "There have been a number of hunter movement and habitat-use studies done in the past using hunter-marked maps, and those maps were accepted without question as accurate. This study essentially calls into question the conclusions of those studies."
Stedman says this was the first time GPS technology was used in a large sample size to study hunter movement. By comparing where hunters actually went with where they said they went, researchers learned that many hunters aren't very good at judging distances, he explains.
"Having hunters wear GPS units allowed us to essentially follow them into the woods," Stedman says, "to see how and where they hunted. The results were surprising."
Factors such as temperature, weather conditions and the perceived deer population in the study area all play into hunter densities, Diefenbach notes. "Hunting pressure on the publicly owned tracts in the northcentral region has fallen drastically, in part, because deer are everywhere in Pennsylvania now," he says. "You don't have to travel to the big woods to hunt, and many areas of the state have more and bigger deer. Soils are better in the southern and western parts of the state, and the habitat is healthier there.
"A big part of the reason there are fewer deer today in the big woods is that there were too many deer in the big woods 20 to 30 years ago," Diefenbach adds, "and the animals overbrowsed the habitat to the point where the region can no longer support as many deer."
Early in the study, researchers tried to keep track of how many deer were harvested by participants. But they abandoned the effort because, in Diefenbach's words, "there were so few deer killed it wasn't worth the effort." The experience has left him convinced that hunter harvests are having little impact on deer numbers in the big-woods region.
"That was the real eye-opener for me," he adds. "About half of the Sproul State Forest is beyond a third of a mile from any road that can be traveled by a vehicle, and the deer that live in those more-isolated areas are rarely threatened by a hunter. It looks like hunters are not killing enough deer in the big woods for harvest to play a role in management of the herd."
Another unexpected development for researchers was that there were more bear hunters than deer hunters in Sproul State Forest. "Four times as many," Diefenbach says. "The foresters told us that the hunting camps in the area were full of bear hunters the week before, but after the first few days of deer season, many of the camps were closed up and empty. "Given that we know that there are 800,000 to 900,000 deer hunters in the state and there are about 120,000 bear hunters, we were amazed to find more bear hunters," Diefenbach notes. "The bear hunting in the Sproul forest is excellent, but still there are far fewer bears than deer up there."