Foraging is the act of searching for food. As a field of study, 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 the foraging options that deliver the highest payoff should be favored by foraging animals because it will have the highest fitness payoff. More specifically, the highest ratio of energetic gain to cost while foraging. Human societies that subsist mainly by foraging wild plants and animals are known as hunter-gatherers.
Optimal foraging theory was first proposed in 1966, in two papers published independently, by Robert MacArthur and Eric Pianka, and by J. Merritt Emlen. This theory argued that because of the key importance of successful foraging to an individual's survival, it should be possible to predict foraging behavior by using decision theory to determine the behavior that would be shown by an "optimal forager" - one with perfect knowledge of what to do to maximize usable food intake. While the behavior 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 behavior. Departures from optimality often help to identify constraints either in the animal's behavioral or cognitive repertoire, or in the environment, that had not previously been suspected. With those constraints identified, foraging behavior 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:
In recent decades, optimal foraging theory has often 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 socio biological 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:
It has been demostrated on Elysia clarki for the first time in animals in 2011, that photosynthetic capability affects foraging behavior under starvation.