AUTHORS: Stephen L. Webb, Noble Research Institute, LLC, Ardmore, OK; Andrew R. Little, Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA; Kenneth L. Gee, Oaks and Prairies Joint Venture, Gene Autry, OK; Steve Demarais, Department of Wildlife, Fisheries and Aquaculture, Mississippi State University
ABSTRACT: In North America, white-tailed deer (Odocoileus virginianus) are the most abundant and widely distributed deer species, resulting in its popularity as a game species. Hunting accounts for most mortality; therefore, hunters influence population dynamics of the species. At the same time, hunters pose an indirect risk to deer whereby human predation risk [1] can alter the behavior and spatial distributions of animals. These risk effects can impact fitness-producing activities where animals must make trade-offs between avoiding risk and energy acquisition [2].
Response to human predation risk can be evaluated by examining movement behavior and those behaviors stemming from the movement process (e.g., space use patterns, distribution [resource selection]). Deer may adopt strategies such as decreased movement and space use, and increased use of security cover to minimize disturbance and the risk of being observed, which translates into reduced risk of harvest [3-5].
In this study, with spatial and temporal controls, we examined how hunters impacted adult (≥2.5 years), male white-tailed deer behavior (i.e., area of use size, refuge use, movement, resource selection, and observability) in southern Oklahoma at three risk treatment levels (i.e., control = no risk; low-risk = 1 hunter/250 ac; and high-risk = 1 hunter/75 ac) over the course of a 36-day study period, including both non-risk and risk periods. Deer were fitted with GPS collars programmed to record GPS relocations every 8 minutes over the 36-day study period. We captured 45 male deer, but analyzed data on 30 unique deer; 7 of which were collared during both years (2008: n = 19; 2009: n = 18).
Eleven deer succumbed to mortality as a result of illegal harvest (n = 8), legal harvest (n = 1), natural mortality (n = 1), and deer-vehicle collision (n = 1). Deer responded to the presence of hunters on the landscape by adapting movement and resource selection strategies both spatially and temporally to avoid potential contact with hunters. These altered behavioral patterns influenced the probability of being observed; collared male deer and all un-collared deer were observed more frequently early during the hunting season progressively declining to the end of the 16-day hunting season. During the study, deer reduced micro-ranges and movement distance, and increased site fidelity by using smaller areas more intensively; the greatest reduction in space use behavior occurred during the 16-day hunting season. Deer altered their resource selection by increasing use of forested areas to reduce the risk of detection, meaning that deer perceived open habitat types as the riskiest places and moved through these at greater speeds.
Understanding the effects of hunting pressure on deer behavior can be used to explain decreased observation rates later in the season, facilitate or reduce harvest based on population management objectives, and help manage hunter expectations regarding observations and harvest. Based on these findings, if the goal is to facilitate harvest, then encouraging early season harvest can help meet harvest management goals because deer have not yet responded to risk on the landscape where movement, resource selection and observability are altered. These data also highlight the adaptive ability of male white-tailed deer to risk where deer show generalized changes in behavior, but also respond in situation-specific manners.
