Comparative effects of group size on the success of wolves attacking (a) and capturing (b) bison and elk.

<p>Lines are population-averaged fitted values from the best-fit GLMMs of wolves hunting bison (Fig. 2a–b in this study; N = 106–218 wolf-bison encounters) and elk (Fig. 1a, 1c in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0112884#pone.0112884-MacNulty1" target="_blank">[10]</a>; N = 235–355 wolf-elk encounters). Slopes were statistically different from zero before each breakpoint (β = 0.34–0.52, SE = 0.09–0.19, <i>P</i><0.001–0.05) but not after (β = −0.21–0.11, SE = 0.05–0.32, <i>P</i>>0.10–0.50), indicating that success was effectively constant beyond each breakpoint. Shaded areas (dark = bison; light = elk) highlight uncertainty about the location of each breakpoint as identified in the confidence set of spline models (ΔAICc <2) for each analysis (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0112884#pone.0112884.s001" target="_blank">Table S1a–b</a> in this study; <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0112884#pone.0112884.s001" target="_blank">Table S1a and S1c</a> in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0112884#pone.0112884-MacNulty1" target="_blank">[10]</a>). Identical methods were used to collect and analyze data for each species.