Competition potential between sympatric woodland caribou and wood bison in southwestern Yukon, Canada

• Published in: Canadian Journal of Zoology
• Main Authors: Fischer, Lisa A, Gates, C Cormack
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2005
• Subjects: Bison bison athabascae; Rangifer tarandus; Wood Bison; Beringia; Bison bison bison; Yukon
• Online Access: http://dx.doi.org/10.1139/z05-117; http://www.nrcresearchpress.com/doi/pdf/10.1139/z05-117

Wood bison (Bison bison athabascae Rhoads, 1898) were reintroduced to the Aishihik Lake area in the southwestern Yukon, where a population of woodland caribou (Rangifer tarandus caribou (Gmelin, 1788)) existed. These species co-occurred in nearby Beringia over several hundred thousand years and in the study area throughout most of the Holocene. We hypothesized that resource-selection patterns should differ widely between species at all scales because co-evolution should have resulted in strong patterns of resource partitioning. We compared winter utilization distributions of both species based on aerial survey data and assessed differential resource selection at the scales of landscape and distributional overlap. We also assessed differential resource use within feeding sites and compared late-winter diets of the two species. We found 41% overlap in 95% utilization distributions but only 6% overlap in 50% utilization distributions. Strong differences were measured for use of space and terrain, including elevation, slope, and distance from permanent water bodies. Bison strongly selected for or used graminoids, while caribou selected for or used lichens at each scale. Overlap in winter diet between the two species was 10%. At current densities, exploitative competition in winter between these species is unlikely.