FORAGING STRATEGY OF A GENERALIST PREDATOR TOWARD A SPECIAL PREY: COYOTE PREDATION ON SHEEP

Abstract

How predators select domestic relative to wild prey is of relevance to dep- redation management and presents opportunities to investigate foraging theory as applied to mammalian carnivores. Domestic prey have numerous qualities that should increase their energy value to predators relative to wild prey. However, whether a predator specializes on domestic prey should also depend on the relative importance of energy efficiency and nonfood-related activities to the predator's fitness, as well as the composition of the alter- native prey base. We used radiotelemetry, carcass surveys, and fecal analysis to investigate (1) whether breeding coyotes killed sheep disproportionately to sheep abundance, (2) wheth- er coyotes consumed wild prey disproportionately to wild prey abundances, and (3) the effects of sheep abundance on consumption of five principal wild prey. Coyote pairs killed sheep in proportion to sheep abundance within territories, suggesting that coyotes did not specialize on sheep. Occurrences in scats of four small wild mammalian prey were not significantly correlated with abundance of sheep in territories, but occurrence of deer in scats was negatively correlated with abundance of sheep in territories. Small prey generally comprised a minor portion of the coyote diet. During the lambing period, consumption of deer was lower where sheep were available than where they were not and was inversely correlated over time with sheep predation rate. During the non-lambing period, when only larger sheep were present, consumption of deer was similar where sheep were available and where they were not, and there was no significant relationship between monthly con- sumption of deer and sheep predation rate. Because coyotes did not specialize on sheep, lambs, or any other prey, these results suggest that their foraging strategy emphasized minimizing time spent with food acquisition over maximizing net energy gain.