LISTEN TO THE AUDIO VERSION
Wood Bison (Bison bison athabascae)
Prey selection by predators is a complex process, with acquisition strategies varying between generalists and specialists. However, generalist predators like wolves (Canis lupus Linnaeus, 1758), can select prey in response to increases in abundance or vulnerability of the prey, often influenced by environmental conditions. In multi-prey systems that include Bison (Bison bison Linnaeus, 1758), this is not always the case, as wolves will often select less dangerous prey. To investigate the predator-prey relationship between wolves and a small (~275 – 300 individuals) Threatened herd of wood Bison (Bison bison athabascae Linnaeus, 1758) in northeast Alberta, Canada, I monitored location data from global positioning system (GPS) collars affixed to both species for one year. I evaluated seasonal differences in wolf diet, the effect of temporal variables on relative Bison predation risk by wolves, and space use relative to Bison for three wolf packs whose territories overlapped with the Bison herd’s home range. I used wolf GPS collar data to find and investigate wolf location cluster sites for prey remains and collected wolf scat to assess seasonal diets. I used consecutive winter days as a measure of winter duration along with daily measures of temperature and snow depth to assess how relative Bison predation risk changes through the winter season. Further, I assessed seasonal differences in wolf movements relative to Bison to decipher whether wolves were opportunistically preying on Bison or actively selecting for them during times of greater Bison vulnerability. Seasonal changes in prey selection from beaver (Castor canadensis Kuhl, 1820) in summer (77%) to cervids (White-tailed deer (Odocoileus virginianus Zimmerman, 1780) and moose (Alces alces Linnaeus, 1758)) in winter (70%) was consistent with other boreal systems. Wolves began preying on wood Bison later in winter when snow depths exceeded 30 cm. While wolves were within the Bison range, they spent significantly more time in areas highly frequented by Bison in late winter relative to early winter. This suggests that wood Bison predation risk is higher with longer winter durations and deeper snow depths that make them more vulnerable, and wolves respond to the vulnerability of this profitable, but rarely obtainable prey source.