Cougar Prey Selection in a White-Tailed Deer and Mule Deer Community

Cooley at al. (2010)

Widespread mule deer (Odocoilus hemionous) declines coupled with white-tailed deer (O. virginianus) increases prompted us to investigate the role of cougar (Puma concolor) predation in a white-tailed deer, mule deer, and cougar community in northeast Washington, USA. We hypothesized that cougars select for and disproportionately prey on mule deer in such multiple-prey communities. We estimated relative annual and seasonal prey abundance (prey availability) and documented 60 cougar kills (prey usage) from 2002 to 2004. White-tailed deer and mule deer comprised 72% and 28% of the total large prey population and 60% and 40% of the total large prey killed, respectively. Cougars selected for mule deer on an annual basis (amd 1⁄4 0.63 vs. awt 1⁄4 0.37; P 1⁄4 0.066). We also detected strong seasonal selection for mule deer with cougars killing more mule deer in summer (amd 1⁄4 0.64) but not in winter (amd 1⁄4 0.53). Cougars showed no seasonal selection for white-tailed deer despite their higher relative abundance. The mean annual kill interval of 6.68 days between kills varied little by season (winter 1⁄4 7.0 days/kill, summer 1⁄4 6.6 days/kill; P 1⁄4 0.78) or prey species (white-tailed deer 1⁄4 7.0 days/kill, mule deer 1⁄4 6.1 days/kill; P 1⁄4 0.58). Kill locations for both prey species occurred at higher elevations during summer months (summer 1⁄4 1,090 m, winter 1⁄4 908 m; P 1⁄4 0.066). We suspect that cougars are primarily subsisting on abundant white-tailed deer during winter but following these deer to higher elevations as they migrate to their summer ranges, resulting in a greater spatial overlap between cougars and mule deer and disproportionate predation on mule deer.

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