Predicting White-tailed Deer Carrying Capacity Using Grazeable Biomass and Tame Deer

Density-dependent population models likely are inappropriate for whitetailed deer (Odocoileus virginianus texanus) in southern Texas due to variable precipitation. We used a tame-deer technique to estimate carrying capacity and correlated results with precipitation and forage biomass. Carrying capacity estimates using digestible energy (DE) consumed by 12 deer were determined using 2 treatments (supplemented and non-supplemented) during 7 trials. Deer were placed in 14 0.33-ha randomly-located enclosures between May 1990 and May 1991. Mean estimates were 0.62 deer/ha/year (SE = 0.27) for non-supplemented enclosures and 1.00 deer/ha/year (SE = 0.57) for supplemented enclosures. Low estimates occurred during summer and high estimates occurred during spring. Precipitation (cm) and forage biomass (kg/ha) were estimated for each trial. Correlations (P <0.05) were positive between carrying capacity estimates and live biomass, forbs, grass, and precipitation, and negative between carrying capacity and dead biomass for the supplemented enclosures. Multiple regression analysis indicated that dead biomass and precipitation were the most significant variables for use in a predictive model. The tame-deer technique for estimating carrying capacity may be useful for determining environmentally stressful periods and aiding decision-making in population management of large herbivores.

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