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For the material that is eaten by foraging by animals, see Forage.

Foraging theory is a branch of behavioral ecology that studies the foraging behavior of animals in response to the environment in which the animal lives. Foraging theory considers the foraging behavior of animals in reference to the payoff that an animal obtains from different foraging options. Foraging theory predicts that foraging options that deliver the highest payoff, should be favoured by foraging animals because it will have the highest fitness payoff.

Robert MacArthur and Eric Pianka, and in an independent paper J M Emlen 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 of 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 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.

• Emlen, J. M. (1966). The role of time and energy in food preference. American Naturaist, 100, 611-617.
• 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.
• Stephens, D. W., Brown, J. S., & Ydenberg, R .C. (2007) Foraging: Behavior and Ecology. Chicago: University of Chicago Press.

• African Pygmies food gathering. Foraging in the rainforest
• Institute for the Study of Edible Wild Plants and Other Foragables. [1]
• Sosis, Richard. (2000), The emergence and stability of cooperative fishing on Ifaluk Atoll, for Human Behavior and Adaptation: an Anthropological Perspective, edited by L. Cronk, N. Chagnon, and B. Iro ns, pp. 437-472. Article