Continent-wide differences in diet breadth of large terrestrial carnivores: the effect of large prey and competitors

Despite their importance for understanding consumer-resource dynamics, the dietary responses of large terrestrial predators to variations in prey richness and competition pressure are unclear. While a greater predator selectivity along with increasing prey abundance would be expected under an optimal foraging scenario, there is some evidence that predators may broaden their diet where there is a greater resource diversity. Furthermore, the use of large prey may be limited by increasing presence of competitors. We considered three widespread large carnivores (the grey wolf Canis lupus, the puma Puma concolor and the leopard Panthera pardus), whose distribution range encompasses different continents, with different communities of prey/competitors. We expected that the potential to modulate their use of large prey according to prey richness would vary according to different levels of potential competition. We collated data from more than 240 studies of the diets of wolf, puma and leopard to model whether the relationships between the diversity of used large prey (i.e. the Large Prey Index) and prey richness was modulated by carnivore richness, in different continents. The wolf showed an increase in the Large Prey Index with prey richness across its distribution range, where it is usually the apex predator in areas from which data are available. Conversely, the leopard showed this pattern in Asia, but not in Africa, where it often coexists with a greater array of potential competitors. For the puma, the Large Prey Index increased with prey richness throughout its distribution range, except in the areas where the larger and dominant jaguar also occurred. By emphasising the complex relationships between prey richness and predator diets, our results testify to the suppressive effects of larger competitors over the use of large prey by subordinate carnivores.