Chapter 28 Effects of Snow and Landscape Attributes on Bison Winter Travel Patterns and Habitat Use

Movement patterns evolved among animal species in response to diverse ecological pressures, including to find new resources, escape predation pressure, find new mates, and improve reproductive potential (Dobson 1982). As the bison (Bison bison) population in Yellowstone National Park increased following the cessation of intensive management in the late 1960s, bison began moving from isolated herds in the interior of the park to contiguous habitat along the western and northern boundaries. Climate (e.g., winter severity) may have exacerbated such movements by reducing the availability of forage (Clutton-Brock et al. 1985, Gaillard et al. 2000, Sæther 1997). Also, human actions to the landscape (e.g., roads, fences) can modify habitats in ways that result in profound changes in ungulate distribution. However, the underlying ecology of bison movements and the influence of natural and anthropogenic features in the Yellowstone landscape are not well documented in the peer-reviewed literature (Gates et al. 2005). We instrumented 30 adult female bison from the central herd with Global Positioning System collars during three winters (2003-2004 through 2005-2006) to quantify how snow, topography, habitat attributes, and roads influenced bison travel patterns and non-traveling activities (i.e., foraging, resting). We used a behaviorally-based resource selection analysis to document: (1) spatial trends in bison travel and non-traveling activities, (2) dynamic and static landscape attributes affecting these patterns, and (3) the influence of snow pack on the odds of bison travel and non-traveling activities.