Research offers insight for Pennsylvania deer hunters

October 17, 2008

Hunters interested in how and why yearling bucks disperse should be intrigued by the findings of a collaborative research project on white-tailed deer conducted by Penn State, the Pennsylvania Game Commission and the U.S. Geological Survey.

"You hear a lot of talk among hunters and landowners about trying to retain or protect deer with superior genes on their properties," said Duane Diefenbach, adjunct associate professor of wildlife ecology and leader of the Pennsylvania Cooperative Fish and Wildlife Research Unit, housed in Penn State's School of Forest Resources. "The truth is that it appears yearling males are going to disperse no matter what -- on average 70 percent of them will disperse three to six miles.
"The effects of Pennsylvania's antler restrictions, increased harvest of does and added attention to quality deer management by landowners and deer-hunting enthusiasts have not affected overall dispersal -- just the timing of it," Diefenbach added. "This latest research has discovered why this is so."
Published in a recent issue of Behavioral Ecology, the four-year research project was part of the Game Commission's evaluation of changes resulting from antler restrictions aimed at allowing male deer to grow older. The study involved 500 radio-collared deer from Centre and Armstrong counties that ended up in 10 other surrounding counties.
Christopher Rosenberry, Game Commission deer and elk section supervisor and one of the lead researchers, noted that the combination of antler restrictions and increased harvests of does in recent years to control deer numbers boosted the number of adult males in the population and decreased the number of adult females. “This resulted in changes in dispersal behavior of yearling male white-tailed deer," he said.
The research yielded the following conclusions that Diefenbach believes are of interest to Pennsylvania hunters and landowners:
-- Fewer yearling males will disperse in the spring if more adult females are harvested the previous fall, because orphaned males are less likely to disperse. In addition, lower harvest rates on bucks (due to antler restrictions) result in an older male age structure, which increases mate competition in the fall and increases fall dispersal rates of yearling males.
"But the net result -- fewer dispersals in the spring and more in the fall -- is that the same percentage of yearling males end up leaving their natal home range," Diefenbach said. "In Pennsylvania, that appears to be about 70 percent."
-- In Pennsylvania, if you see a yearling buck on your property in May or June, there is a 30 percent chance that by July he will have dispersed and left the property. By the fall hunting seasons, there is a 70 percent chance he will have dispersed to a new location. This means that by the fall hunting seasons, seven of 10 yearling male deer on your property likely will have immigrated from somewhere else.
-- Depending on the amount of forest on the landscape, those deer may come from as few as one or as many as 30 miles away.
"But probably the most significant finding of this research for hunters and landowners," said Diefenbach, "is that if you see a yearling male on your property after the hunting season, there is a 90 percent chance he will survive and be on your property the following hunting season. That shows that antler restrictions result in more older bucks."
The research, which occurred between 2001 and 2005, was unique, according to Diefenbach. "The questions of why and how young, male white-tailed deer disperse are fundamental to the species, not just Pennsylvania deer," he said. "This study is exceptional because state agencies rarely make large changes to deer-hunting regulations -- and if they do, they rarely study the results."
Other states, such as Georgia and Arkansas, have implemented antler restrictions in the last few decades, but they never took the time and effort to study the results the way Pennsylvania has, Diefenbach pointed out. "We never would have learned what we did if the Pennsylvania Game Commission had not funded this large-scale experiment after it made major changes to deer-hunting regulations," he said.
There is a lot of interest among hunters and landowners these days to manage their hunting land for quality deer -- larger, older bucks and a deer population in balance with the habitat, noted Diefenbach. “This research shows that worrying about genetics is fruitless because many bucks on your property may come from miles away,” he said. “For those interested in this type of management, the best you can do is protect yearling bucks during the hunting season and provide quality habitat the rest of the year.”

(Media Contacts)

Last Updated March 19, 2009