Large Mammals Research: Deer Population Monitoring and Management

Our objective of this research is to quantify the accuracy of sex-age-kill (SAK) population estimates and harvest predictions including evaluating impacts by input variables and explore other population models to determine their effectiveness to estimate deer populations.

Background

Historically, annual deer population estimates have been based on pellet-group counts, deer-trail surveys, and sex-age-kill (SAK) estimates (Creed et al. 1984, McCaffery 1976). Pellet-group counts were discontinued in 1978 because of the high variability of management unit-specific estimates and the large amount of labor needed to complete the surveys (Creed et al. 1984). Deer-trail surveys were discontinued in 1983 because of personnel shortages, variable training and interest of observers, and the effects of weather on trail formation (McCaffery 1984). Since that time the Department of Natural Resources has relied exclusively on SAK estimates for monitoring trends in deer population status and formulating harvest strategies. The SAK index relies heavily on the assumption that the annual buck harvest rate is consistent from year to year for individual management units. Sensitivity analyses have shown that SAK estimates are most sensitive to biases in estimates of adult buck harvest rates (Cary 1987).

During the 1970´s and 1980´s, the hunting season framework was relatively stable in Wisconsin resulting in apparently stable buck harvest rates. Recently, across much of southern Wisconsin, the age composition of harvested bucks has changed, with bucks > 2 years of age composing a higher percentage of the harvest. This is suggestive of a lowering of adult mortality rates. In 1996, dramatically changed deer hunting seasons in the south to reduce the deer population will undoubtedly have impacts on the performance of the SAK. Recent changes in the geographic distribution of hunters and hunting seasons may have affected buck harvest rates. The SAK and alternate models need to be evaluated to insure accurate population estimates are being provided to manage the deer herd.

This study is expected to increase the understanding of factors affecting the harvest of white-tailed deer and rate of population increase which will lead to a better understanding of the accuracy and precision of the current deer population monitoring and harvest management system and the development of procedures to increase the accuracy and precision of population estimates and harvest predictions. This information is needed to increase the public´s confidence in the Department's deer management program and willingness to harvest the number of antlerless deer required to maintain populations at goal levels. Maintaining deer populations closer to goal levels will reduce the negative social and ecological consequences of over-abundant deer populations while maintaining opportunities for harvest and wildlife viewing.

For more information on this topic, please contact:
Robert Rolley
(608) 221-6341