Management Implications of Foraging Theory: Evaluating Deer Supplemental Feeding

I conducted an experiment in a northern deer yard to compare the foraging behavior of naturally wintering and supplementally fed white-tailed deer (Odocoileus virginianus) and to assess when supplemental feeding might be warranted. Deer survived on natural browse an 1 area of the yard and were provided ad libitum supplemental feed in another. I examined the effects of browse depletion and accumulating snow on diet selection in 3 winter sampling periods. I used an optimal foraging model to predict the diet for 2 potential strategies: 1) energy maximization, where deer maximize their energy intake to maximise survivorship, and 2) time minimization, where deer satisfy energy need in the least feeding time thereby minimizing exposure to deleterious climate. Deer selected energy maximizing diets in all time periods and feeding areas. Naturally wintering deer were expected to select a mixed diet of coniferous and deciduous browse. Predicted diets (deciduous:conifer) for the 3 time periods were 1,130:46, 780:330, and 589:462 g dry mass per day. Observed diets for the same time periods were 1,090:65, 684:317, and 452:490 g dry mass per day. Naturally wintering deer satisfied requirements for survival, so supplemental feed was not required for winter conditions during the study. Supplementally fed deer were expected to eat only supplemental feed in all sampling periods. Contrary to predictions, they continued to eat browse. A sensitivity analysis, used to examine the reliability of model predictions because of variable parameter estimates, indicated the model predictions were robust. Thus, I concluded that the supplemental feeding program may have been inefficient. Supplemental feed was delivered in a few large feeders, which created a limiting resource. This probably increased competition at feeders, forcing individuals to browse