Winter severity modulates the benefits of using a habitat temporally uncoupled from browsing

Abstract

Citation: Giroux, M.-A., C. Dussault, J.-P. Tremblay, and S. D. Côté. 2016. Winter severity modulates the benefits of using a habitat temporally uncoupled from browsing. Ecosphere 7(8):e01432. 10.1002/ecs2.1432Abstract. Resources whose abundance is not affected by the density of the consumer population, namely donor-controlled resources, are ubiquitous. Donor-controlled resources can act as food subsidies when they sustain consumer populations at higher densities than what would be predicted without donorcontrolled dynamics. Herbivore populations that have access to food subsidies may reach and maintain high densities, with potential major ecological and economic consequences. A better understanding of the roles of food subsidies on temperate herbivores will likely be achieved by simultaneously taking into account other drivers of demographic variations such as winter severity. Here, we tested the hypothesis that the use of a donor-controlled food resource that may act as a food subsidy, namely balsam fir (Abies balsamea), and winter severity act together to shape the patterns of overwinter mass loss in a large herbivore population (white-tailed deer, Odocoileus virginianus). We monitored weather conditions, diet, habitat use, and mass loss of female deer during two highly contrasted winters. During an exceptionally milder winter, characterized by shallower snow depth and warmer windchill temperatures, female deer shifted their diet toward resources usually covered by snow during typical winters. Surprisingly, the rate of body mass loss remained similar during the milder and the harsher winter. The rate of body mass loss rather decreased with the use of balsam fir stands during the harsher winter, but increased with that same variable during the milder winter. Our study revealed that deer can alleviate overwinter mass loss by using a donor-controlled habitat type temporally uncoupled from browsing, but that this benefit is climate dependent. This study represents an additional step to address the largely unexplored concept of how temporal uncoupling between resources and consumer dynamics may contribute to sustain consumer populations at higher densities than predicted without considering donor-controlled dynamics.

Snow depth, soil temperature and plant–herbivore interactions mediate plant response to climate change

“…Climate changes across seasons could also have important indirect ecological effects on temperate forests by shifting trophic and species interactions, particularly in response to a smaller winter snowpack (Penczykowski, Connolly, & Barton, 2017). For example, increased accessibility to vegetation with a smaller snowpack has been shown to shift browsing behaviours of large herbivores like moose (Christenson, Mitchell, Groffman, & Lovett, 2014) and deer (Giroux, Dussault, Tremblay, & Côté, 2016). Likewise, a relatively shallow snowpack also influences small herbivores by reducing temperatures in the subnivean space between the soil and snow surface (Petty, Zuckerberg, & Pauli, 2015), which is an important refuge for small mammals in winter (Williams, Henry, & Sinclair, 2015).…”

Climate change effects on deer and moose in the Midwest

“… b Pauley et al (); Dumont et al (); Jenkins et al (); Lefort et al (); Kittle et al (); Månsson (); van Beest et al (); Witt et al (); Massé and Côté (, ); DelGiudice et al (); Giroux et al (); Courbin et al ().…”

Spatial correlations between browsing on balsam fir by white‐tailed deer and the nutritional value of neighboring winter forage

“…Low nutritional quality of neighboring plants should also be correlated with either high (associational susceptibility) or low (associational defense) browsing on fir. We investigated these relationships on a predator‐free island, where forage selection should mainly be driven by forage characteristics, deer nutritional state, abiotic environmental factors, and locomotion costs (Giroux, Dussault, Tremblay, & Côté, ; Massé & Côté, , ).…”