Dispersal of yearling male white-tailed deer (Odocoileus virginianus) can have profound effects on population demographics and can adversely affect population estimates and management objectives. The relationship among population demographics, social pressures, and dispersal ecology is not clear and warrants scientific evaluation. The age structure and sex ratio of the white-tailed deer population at Chesapeake Farms, Maryland, USA, changed after implementation of quality deer management (QDM). Following Rosenberry's (1997) pre-QDM study on white-tailed deer dispersal, we conducted a post-QDM study on white-tailed deer dispersal at Chesapeake Farms. The objectives of our study were 1) to compare pre- and post-QDM emigration, immigration, survival, and behaviors of yearling males, 2) to evaluate inbreeding avoidance and sexual competition hypotheses as mechanisms of dispersal through behavioral comparisons of dispersers and nondispersers, and 3) to evaluate the maternal aggression hypothesis by comparing dispersal rates of orphan and non-orphan yearling males determined by genetic maternity analysis. Emigration probability of yearling males 8–18 months of age pre-QDM was 0.70 ± 0.07, and post-QDM was 0.54 ± 0.10 (Z = 1.39, P = 0.165). Survival probability of yearling males 8–18 months of age increased from 0.44 ± 0.07 pre-QDM to 0.72 ± 0.08 post-QDM (Z = 2.82, P = 0.005), and we attributed this increase largely to increased survival of emigrant males post-QDM. Dispersers exhibited breeding competition with other yearling males more often than nondispersers in both pre- (t19 = 3.22, P = 0.005) and post-QDM (t13 = 3.54, P = 0.004) populations. Breeding behaviors of yearling males decreased from pre- to post-QDM (t34 = 2.00, P = 0.053). Antler points of nondisperser yearlings also decreased from pre- to post-QDM (t16 = 3.29, P = 0.005). DNA maternity analysis indicated that dispersal of orphans (4 of 7) and non-orphans (7 of 10) was similar (= 0.298, P = 0.585). Our results fail to support inbreeding avoidance and support sexual competition as a cause of autumn dispersal at Chesapeake Farms. Through QDM, an older male age structure may have suppressed breeding competition in yearling males and decreased dispersal rates, increasing site-specific management efficiency
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Vol. 70 • No. 5