Land use and dispersal influence mortality in white-tailed deer
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Restoring male age structure in whitetailed deer populations has become an important objective for many state agencies aimed at improving herd dynamics. Limiting mortality in the yearling (12 yr old) age class is a primary consideration, and regional differences in climate, habitat characteristics, hunting regulations, and hunter behavior complicate the understanding of how specific factors influence the risk of mortality. We used Cox proportional hazard modeling to determine the effects of body size, mean distance to road, dispersal behaviors, use of forested land, and use of land open to public hunting on the risk of mortality for a population of radiocollared, yearling males (n = 76) in Sussex County, Delaware, USA. Annual survival averaged 0.55 (95% CI = 0.450.68), with harvest accounting for 79% (26/33) of all mortalities. Measurements of body size (chest girth, shoulder height, and total length; cm) influenced dispersal probability but not dispersal distance. The best approximating model for mortality risk included a covariate for landownership, whereby mortality risk increased on public land. Among males who dispersed, longerdistance dispersal was associated with reduced mortality, which contradicts previous research describing dispersal as a highrisk behavior. The effect of landownership on mortality risk has not been previously identified, especially when regulations regarding harvest of yearling males are similar between landownership types. We observed annual survival rates of 0.69 (95% CI = 0.570.82) for deer apparently using private land exclusively during the hunting season, and 0.20 (95% CI = 0.110.48) for deer that used public land during the hunting season. Survival rates on private land were comparable to those of other regions actively managing male age structure. These results suggest survival of yearling males in the region is influenced by hunter harvest and the risks associated with dispersal may be minimal in areas where harvest pressure is low, although hunter harvest on public land may limit male age structure on a localized scale. The Wildlife Society, 2019
