Equating Currencies of Predation Risk with Energy Maximization

Animals forage for resources in the face of ecological constraints (Mangel and Clark 1986). Foraging often occurs under the watchful eye of a predator. The risk of predation is an ever-present danger and an animal’s foraging behavior reflects this risk even in the physical absence of an actual predator. Vigilance is the state of arousal required for an alert animal to detect predators (Lima and Dill 1990). Animals pay a price of decreased intake as a cost for the increased vigilance required under the risk of predation. The nature of the risk is entirely analogous to the way theft can structure human society. How many of us have seen a thief stealing something of ours? Even though the actual frequency with which we have something stolen is low, the threat of theft leads us to certain preventative behaviors. Because theft is a reality, we pay a penalty that is staggering to comprehend. Think of a society without theft. No locks on cars, no lock downs for computers, no car alarms, and no theft insurance. On a slightly grander scale, no countries would attempt to steal land, and thus, perhaps no money would need to be spent on defense, therefore there would be no war. Animals pay similar penalties for their vigilance. Because the actual occurrence of predation is rare (an individual is only killed by a predator once), most studies of predation and foraging involve placing animals under the baleful eye of a stuffed predator. Foragers face risks from predators who are themselves foraging in the environment for their own prey. A spider forages for flies, while a bird forages for spiders. All of these factors reflect the social and ecological constraints on foraging.