Buck Study Gains Momentum
Halfway through an unprecedented three-year study that is tracking the lives of whitetail bucks, the Pennsylvania Game Commission reports that it is acquiring important data that will help improve the agency's deer management program and help wildlife managers better understand the white-tailed deer's world.
About 200 radio-tagged bucks currently are being followed electronically in study areas in Armstrong and Centre counties. The research effort - a partnership involving the Pennsylvania Cooperative Fish and Wildlife Research Unit, Pennsylvania State University and the Game Commission - is believed to be the largest radio-telemetry dispersal study of whitetails ever conducted in the United States.
"When you get right down to it, no species in this Commonwealth influences and impacts the lives of residents and wildlife more than white-tailed deer," said Dr. Gary Alt, who supervises the Game Commission's Deer Management Section. "That's why the Game Commission is continually adjusting its research program to include more fieldwork on whitetails. This study is providing data that will help us better understand deer and their movements, and enhance our management of this important resource to meet economic and recreational demands and limit conflicts. So far, the field work has been demanding, but the results have been gratifying."
This study, launched in December of 2001, was designed to monitor deer movements, measure buck survival rates and determine cause-specific mortality. To date, more than 300 bucks have been radio-tagged in the study. About 200 deer with transmitters remain on the air and are feeding data to biologists via radio frequencies.
"What makes this study so incredible is the extraordinary lengths we've gone to just to put transmitters on these deer and the cooperation we have received from landowners who permit capture activities on their properties," explained Bret Wallingford, Game Commission biologist, who is supervising the Centre County study area. "Our field teams have worked long hours, particularly on cold winter nights, to trap these deer. They arranged their schedules to run drop nets five to seven nights a week and then to check clover traps during the day. Over the past two winters, they trapped almost 1,200 deer. In fact, they would have taken more had warm weather and abundant mast crops not limited trapping success in the first year of trapping."
Most of the study bucks were captured over the past two winters by field teams using 70-foot by 70-foot drop nets, rocket nets and clover traps. Deer are more prone to approach a trap when snow covers food supplies or when fall foods and residual agricultural crops aren't readily available.
"It took us some time to adapt our trapping methods to our study areas," noted Dr. Marrett Grund, Game Commission biologist, who is working on the Armstrong County research team. "But once the field teams sorted out what works and what didn't - and colder weather settled in - they really started to catch deer. This past winter, the trapping teams captured nearly 800 deer. From this total 180 button bucks and 20 adult bucks were radio-tagged."
"It's quite a challenge getting deer to approach a trap, given the animal's nervous disposition and flighty response to the slightest hint of trouble or uncertainty," said Eric Long, a doctoral student at Penn State University helping with the research. "But when fall and agricultural foods are available in only limited quantities, or are covered by deep snow, well-placed traps can be very effective."
The study field teams have been monitoring bucks since April and will continue to follow their movements until the teams resume trapping in January. One interesting finding that has already surfaced in the field work is that the use of antler restrictions during last year's deer seasons appears to have increased buck survival. In a typical Pennsylvania deer population not protected by antler restrictions, about 80 percent of the bucks would be taken by hunters. This past winter, about 50 percent of the study bucks - which may be taken by hunters - made it through hunting seasons.
"The initial study results indicate that antler restrictions are working," Alt pointed out. "Our field teams have uncovered this spring that the survival rate of study bucks has increased over the time-honored survival rate established over the past several decades. They also have caught more adult bucks this past winter than they did in the study's start-up year. It's encouraging to see that our antler restrictions appear to be working. This should become even more evident to hunters when they head afield this fall."
One of the major events in the life of a Pennsylvania buck being closely followed in the study is dispersal, or when a yearling buck leaves its parent to establish its own territory. Female yearlings often briefly leave the doe that bore them and then rejoin her after she bears new fawns and they begin to travel with her. Young bucks, conversely, leave and usually do not reunite with their parent doe.
So far, field work has shown that 71 percent of the study bucks in Armstrong County and 44 percent of the Centre County bucks dispersed from the home range they occupied as fawns. Why there's such a substantial difference in the dispersal rates is still open to interpretation. Centre County's habitat is more forested, Armstrong's, more fragmented. Centre had a three-point antler restriction to harvest a buck in most recent deer seasons, Armstrong had a four-point antler restriction. The difference in antlerless harvest levels also may play a role.
"Habitat and hunting pressure are known to influence deer behavior," pointed out Dr. Chris Rosenberry, Game Commission biometrician, who is assisting with the study. "Dispersal itself appears to be a behavior influenced by social interactions. As a young buck grows, its life is relatively stable - it follows its mother around for about a year. Then, when the young buck is about a year old, its mother rejects it as she prepares to give birth to her next fawns. This is a time when we usually see the first dispersal movements. We also see dispersal during the fall, when levels of aggression between bucks increase as the breeding season approaches."
Dispersing bucks in the Armstrong County study also traveled greater distances. On average, Armstrong bucks traveled about seven miles; Centre County bucks, four miles. The farthest dispersal distance recorded for Armstrong was an amazing 26 miles, which included swimming across the Allegheny River, while in Centre it was 16 miles.
Signals followed by field personnel in the study are generated by a transmitter attached to the deer's ear. The transmitter used this spring was modified from the earlier version used in 2002 because nearly half of the ear transmitters placed on study deer in 2002 were lost. It was an unanticipated problem, because researchers reasonably concluded a deer won't grab a transmitter with its hoof or mouth. They didn't count on the deer getting help.
"It appears most of the ear transmitters were pulled out by other deer, possibly while grooming," Rosenberry said. "Although this wasn't out of the realm of possibilities, the number of transmitters lost wasn't expected based on prior experience with ear transmitters. This year, the problem seems to be less severe. Only time will tell for sure, though."
The buck radio telemetry study is one of several studies the Game Commission has performed in recent years to develop a better understanding of Pennsylvania deer. Other work has included a fawn survival study that provided important information and data about fawn mortality and movements; a deer conception study that pinpointed when deer were being bred and born in the Commonwealth; and an antler measurement study that confirmed age and nutrition have an enormous impact on the size of antlers.
The Game Commission continues to maintain web pages that offer background and periodic updates on the buck radio telemetry study. To check out the study section, go to the Game Commission's website (www.pgc.state.pa.us), click on "Wildlife," then choose "Deer in Pennsylvania," and select "Antlered Deer Study."