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Foraging

Foraging just means looking for food (or, metaphorically, anything else). However, it has acquired an important technical meaning within the science of behavioral ecology where it refers to predator-prey interactions (note that in ecology, prey can be plant as well as animals). It is also an important study in social anthropology, particular in relation to societies that follow, wholly or in part, the hunter-gatherer way of life.

MacArthur and Pianka in 1966 first proposed an optimal foraging theory, arguing that because of the key importance of successful foraging to an individual's survival, it should be possible to predict foraging behaviour by using decision theory to determine the behaviour that would be shown by an "optimal forager" - one with perfect knowledge of what to do to maximise usable food intake. While the behaviour of real animals inevitably departs from that of the optimal forager, optimal foraging theory has proved very useful in developing hypotheses for describing real foraging behaviour. Departures from optimality often help to identify constraints either in the animal's behavioural or cognitive repertoire, or in the environment, that had not previously been suspected. With those constraints identified, foraging behaviour often does approach the optimal pattern even if it is not identical to it.

There are many versions of optimal foraging theory that are relevant to different foraging situation. These include:

• The optimal diet model, which describes the behaviour of a forager that encounters different types of prey and must choose which to attack
• Patch selection theory, which describes the behaviour of a forager whose prey is concentrated in small areas with a significant travel time between them
• Central place foraging theory, which describes the behaviour of a forager that must return to a particular place in order to consume its food, or perhaps to hoard it or feed it to a mate or offspring.

In recent decades, optimal foraging theory has frequently been applied to the foraging behaviour to human hunter-gatherers. Although this is controversial, coming under some of the same kinds of attack as the application of sociobiological theory to human behaviour, it does represent a convergence of ideas from human ecology and economic anthropology that has proved fruitful and interesting.

Important contributions to foraging theory have been made by:

• Eric Charnov, who developed the marginal value theorem to predict the behaviour of foragers using patches;
• Sir John R. Krebs, with work on the optimal diet model in relation to tits and chickadees;
• John Goss-Custard, who first tested the optimal diet model against behaviour in the field, using redshank, and then proceeded to an extensive study of foraging in the Common Pied Oystercatcher.

References

• MacArthur, R. H. and Pianka, E. R. (1966). On the optimal use of a patchy environment. American Naturalist, 100, 603-609.
• Stephens, D. W., & Krebs, J. R. (1986). Foraging theory. Princeton NJ: Princeton University Press.
• Winterhalder, B. and Smith, E. A. (Eds.). (1981). Hunter-gatherer foraging strategies. Chicago: University of Chicago Press.