PARENT SESSION
Contributed Oral Session 101: Mammalian Herbivory
Wednesday, August 10, 1:30 PM - 5:00 PM, Meeting Room 520 A, Level 5, Palais des congrès de Montréal
Elk winter foraging at fine scales in Yellowstone National Park.
Fortin, Daniel*,1, Morales, Juan2, Boyce, Mark3, 1 Département de biologie, Sainte-Foy, Québec, Canada2 Ecology and Evolutionary Biology, Storrs, Connecticut, USA3 Department of Biological Sciences, Edmonton, Alberta, Canada
ABSTRACT- The scale at which food characteristics influence the foraging patterns of herbivores is currently unclear. It has been argued that elk (Cervus canadensis) do not differentiate between areas of low and high plant biomass at fine scales, and they simply select feeding stations at random. Our goal was to verify whether fine-scale foraging paths of elk respond to habitat structure in Yellowstone National Park. We gathered foraging information by following snow tracks made by elk grazing in open habitat located on hillsides and on flat terrain. The 21 snow paths surveyed were comprised on average of 15 discrete snow craters connected to each other by relatively straight-line movements. Our analyses revealed two levels of selection: elk chose where to dig, and how much search effort to allocate at digging sites based on spatial habitat characteristics. On hillsides, elk preferentially dug in areas where more biomass of grasses and forbs was available, and simply walked through poorer sites without digging. Individuals also search more intensively, creating larger craters, where food biomass was higher. On flat terrain, crater size decreased with snow depth and increased with snow density. Correlated random walk models usually were adequate to characterize elk movement on flat terrain, but not on hillsides. First, as the number of movements between local foraging areas increased, elk displacements on hillsides became shorter than expected from random patterns. Second, elk tended to forage perpendicularly to aspect, resulting in horizontal displacements. Our study demonstrates that, unlike previous contention, free-ranging elk adjust their foraging to fine-scale habitat structure.
Key words: Movement analysis, Food patch selection, Winter foraging, Elk