39 39 Dispersal Patterns of Male White-tailed Deer in Centre County, PA Milton G. Newberry, III, Penn State Duane R. Diefenbach, Ph.D. U.S. Geological Survey Adjunct Associate Professor of Wildlife Ecology Penn State Eric Long, Graduate Research Assistant School of Forest Resources Penn State Abstract: Dispersal direction of male white-tailed deer (Odocoileus virginianus) has been hypothesized to be influenced by landscape features such as ridges and valleys. We monitored the dispersal distances and directions of 36 yearling males in Centre County during spring dispersal periods 2002-2004 and fall dispersal periods 2002-2003 using radio telemetry. We hypothesized that the dispersal direction of deer would be bimodal and parallel to the ridge lines in the study area (q 0 = 66°, q 1 = 246°). We found no difference in direction between spring and fall dispersal periods, and no difference between years. The mean angles (q 1 = 89, 95% CI = 71-109; q 2 = 269, 95% CI = 251- 289) were different from the direction of the ridgelines. Thus, we concluded that yearling male dispersal is directed but not parallel to the ridges and valleys of Centre County. We recommend future research investigate whether habitat features, natural and man-made barriers, and response to human contact influences dispersal direction. Introduction Dispersal among animals is common and is often considered a means to minimize inbreeding (Shield 1987) and serve as a mechanism for establishing new populations or facilitating species range expansion. However, wildlife managers typically ignore dispersal, assume it to be nonexistent, or assume that immigration and emigration are equal (Rosenberry et al. 1999). Mammalian dispersal is typically male biased to avoid inbreeding (Greenwood 1980) and dispersal is most prevalent among yearling bucks in white-tailed deer (Odocoileus virginianus, Marchinton and Hirth 1984). Social pressures have been hypothesized to prompt natal dispersal of yearling male white-tailed deer during the breeding season (i.e., August to November) or during the fawning season (i.e., May to June). For example, sexual competition with other males (Kammermeyer and Marchinton 1976) and aggression from a yearling male’s mother (Holzenbein and Marchinton 1992a) or related adult females (Ozoga and Verme 1985) has been implicated as potential proximate mechanisms of dispersal. Inbreeding avoidance, as exemplified by