Constraints on active-consumption rates in gray wolves, coyotes, and grizzly bears

Abstract

Predators' feeding strategies lie on a continuum between energy maximizers, who maximize the energy obtained from a patch of food, and time minimizers, who minimize the time required to get a fixed ration of food from a patch. Carnivores that feed on large prey should adopt a time-minimizing strategy by maximizing their active-consumption rate (ACR) if they evolved under conditions of high competition from group members, and conversely adopt an energy-maximizing strategy if they evolved under conditions of low competition from group members and were thus able to monopolize their prey. By provisioning animals with large pieces of ungulate carcasses, we measured ACR for captive gray wolves (Canis lupus), coyotes (Canis latrans), and grizzly bears (Ursus arctos). In accordance with a conspecific-competition hypothesis, ACR increased with sociality. Other factors influencing ACR included subject body mass and food type, ACR being significantly faster on muscle and organs than on bone and hide. Measuring ACR is crucial to empirical and theoretical studies assessing foraging decisions and may be used as an indicator of an animal's competitive environment.