Survival, movement, and habitat selection of adult white-tailed deer in southern Delaware
Date
2017
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Publisher
University of Delaware
Abstract
Chapter 1 of this dissertation examines survival of subadult male white-tailed deer (Odocoileus virginianus) in southern Delaware. Increasing male age structure in white-tailed deer populations has become an important objective for many state managers and private landowners seeking to improve hunter satisfaction while maintaining appropriate deer densities. Limiting mortality in the subadult age class is often the primary consideration, and regional differences in climate, habitat, regulations, and hunter behavior complicate understanding of how specific factors influence the risk of mortality. I used Cox proportional hazard modeling to examine the effects of mean distance to road, mean distance to habitat edge, dispersal behaviors, and landownership on the risk of mortality of a collared population of subadult males (n = 61) in Sussex County, Delaware, USA. Annual survival averaged 0.60 (95% confidence interval = 0.49 – 0.73), with hunter harvest accounting for 79% of all mortalities. The best approximating supported model for risk of mortality included covariates for landownership (public versus private; P < 0.01) and mean distance to habitat edge (P = 0.01), with mortality risk increasing on public land and in closer proximity to habitat edge. Increased mortality risk due to habitat fragmentation is well documented in white-tailed deer; however, the effect of landownership has not been quantified, especially when hunter objectives and harvest behaviors differ between landownership types. I observed annual survival rates of 0.75 (95% confidence interval = 0.62 – 0.89) for deer exclusively on private land during the hunting season, and 0.37 (95% confidence interval = 0.18 – 0.73) for deer that utilized public land during the hunting season. Survival rates on private land were comparable to those of other regions actively managing male age structure (0.72 in Mississippi), although hunter harvest on public land may limit subadult male survival throughout the region. ☐ Chapter 2 focuses on habitat selection in adult male and female white-tailed deer. Individual white-tailed deer can vary in their use of resources and habitats as a function of sex, age, experience, and resource availability. Such individual heterogeneity in habitat use can complicate management efforts, as general management practices may be ineffective for specific objectives at localized scales. I examined heterogeneity in fall and winter habitat selection and functional response using individual conditional logistic step selection models for adult white-tailed deer in southern Delaware. I used fractal analysis to determine the scale at which animals perceived and responded to the landscape, and modeled step selection using covariates for cover type, development, elevation roughness, distance to edge habitat, and distance to road. Magnitude and directionality of selection coefficients were variable among individuals within the same sex. I did not observe uniform individual selection coefficients in any habitat covariate for either sex, and variability in individual selection coefficients was greater in males. Selection coefficients for open habitat (P = 0.03) and distance to road (P = 0.04) were both a function of increasing proportion of open habitat within the home range. Distance to edge habitat was the only landscape covariate where individual selection coefficients were a function of age (P = 0.03), with older deer avoiding habitat edges. Individual models explain heterogeneity in habitat selection that is often overlooked using population level fixed-effect models. Managers attempting to influence harvest success via habitat and population management should be aware of the substantial heterogeneity in habitat use among individual deer before implementing costly practices that may not be appropriate for their specific objectives.
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Keywords
Biological sciences, Adult white-tailed deer, Habitat selection, Movement, Southern Delaware, Survival