A long-term assessment of the effect of winter severity on the food habits of white-tailed deer

Abstract

Nutrition is a critical link between environmental and population variation in northern populations of free-ranging white-tailed deer (Odocoileus virginianus). Yet, few studies have investigated winter food habits of northern free-ranging deer and all of these were short-term studies (1–2 winters). Consequently, little information is available on the effect of inter-annual variation in winter severity on browse availability and diet composition of free-ranging deer. We describe winter browse use by white-tailed deer on 4 study sites in northern Minnesota during 1991–2005. We also tested several a priori predictions about how browse use and availability would change as a function of winter severity. We collected browse data from 1,028 feeding trails and recorded 38 available browse species or species groups. The 4 most common browse species (beaked hazel [Corylus cornuta], mountain maple [Acer spicatum], trembling aspen [Populus tremuloides], and speckled alder [Alnus incana]) accounted for 76% of total available stems, and beaked hazel and mountain maple accounted for 68% of total used stems. As expected, browse use and availability distributions were very similar (i.e., deer used many of the available browse resources). Mean number of browse species used did not increase (decreased selection) with snow depth. However, mean browse rate (functional response) increased with increasing snow depth, and use of speckled alder (starvation food) increased when snow depth exceeded 40 cm. In addition, the number of browse species along feeding trails declined and stem abundance increased, on average, with increasing snow depth. Deep snow and increased use of dense conifer cover in northern Minnesota may restrict deer to greater use of lower quality feeding sites. In landscapes where this may occur, habitat management should attempt to minimize over-browsing on feeding sites in proximity to dense conifer cover by maximizing browse abundance and availability, particularly for beaked hazel and mountain maple. Managers also should consider enhancing alternative early-winter feeding sites. © 2013 The Wildlife Society. © The Wildlife Society, 2013