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White-tailed Deer Research Projects - Predation and Fawn Recruitment Study

The distribution and abundance of predators on Wisconsin's landscape has changed over time. From the time a doe is impregnated to the time the fall hunting season begins, a number of fawns are lost every year to various causes before and after birth including weather, food availability and nutrition, disease, predation, accidents and hunter harvest. This study will measure the role of predation on recruitment which is the number of deer added to the population each year by fawns surviving into the fall. Researchers will gather field data on doe pregnancy rates and litter sizes and fawn survival and causes of mortality from birth to the hunting season. This study will also attempt to identify the specific predators (mainly wolves, bears, bobcats, and coyotes) of fawns and measure the impact predation has on recruitment.

This study will provide another method of estimating deer population growth between the end of a hunting season to the beginning of the next. This is important because precise deer population growth predictions allow wildlife biologists to prescribe the best antlerless harvest quotas in a deer management unit for the following season.

Study Area

Two study areas have been established; one primarily forested area in northwest Wisconsin, and one farmland area in east-central Wisconsin. The different study sites were chosen to encompass variation in buck mortality and harvest rates across areas with different habitat types, hunting pressure, type and relative abundances of predators, and vehicle traffic.

Study Design

Female white-tailed deer (does) will be captured with a variety of methods including box traps, rocket nets, net guns, drop nets, or tranquilizer darts during winter months. We will attempt to minimize the handling time, stress and injury to captured deer. Researchers and volunteers will conduct field ultra-sounds on does to determine the number of fetuses the deer is carrying and to assess relative body condition and effects of winter severity by measuring rump body fat depth. Pregnant does will be fitted with vaginal implant transmitters (VITs) that are released and activated upon giving birth so researchers and volunteers can locate newborn fawns.

When a VIT signal indicates that a doe has given birth, a research coordinator and a group of volunteers will thoroughly search the immediate area for bedded fawns. Upon locating fawns, a small expansion break-away style radio-collar will be fitted on all captured animals. The collars are designed to expand as fawns grow and will fall off as deer reach adult size.

Throughout life of the collar, researchers will monitor the activity of each captured fawn. If a fawn dies while carrying the collar, efforts will be made to locate the carcass and collar to determine the cause of death. If predation occurs, an investigation will be made to identify the predator species based on the nature of the carcass remains and other signs, including extraction of saliva samples from visible bite wounds on radio-collars or deer carcasses.