Optimal Foraging Theory

Origins and basic assumptions

Papers by MacArthur and Pianka and by Emlen, published in the same 1966 issue of a journal, were the starting point for applying the economic idea of optimization to animal behavior. The theory holds that natural selection would have favored individuals that forage efficiently, and it builds models from three components: a currency describing what is maximized, usually net energy gain per unit time; decisions, the range of behaviors an animal can choose; and constraints such as search time, handling time and cognitive capacity. Because this yields quantitative, observable predictions, it can be tested more rigorously than loose stories about adaptation.

The prey model and the marginal value theorem

The prey choice model ranks food items by profitability, energy value divided by handling time, and adds them to the diet in order from most to least profitable. Its key prediction is that whether a low-ranked item is eaten depends not on its own abundance but on how often better items are encountered. Krebs et al. (1977) offered great tits large and small pieces of food on a conveyor belt and found that the birds ignored small items when large ones were plentiful. Eric Charnov's (1976) marginal value theorem addresses when an animal moving between patches of scattered food should leave a patch. As intake within a patch declines, it is optimal to leave when the instantaneous marginal rate of gain falls to the average rate for the environment as a whole. Longer travel times between patches therefore call for longer stays in each, a prediction Cowie (1977) supported in experiments with great tits.

Extensions, critiques and applications

Caraco et al. (1980) demonstrated risk-sensitive foraging, with energy-stressed birds preferring variable food sources, and Lima and Dill (1990) reviewed trade-offs between predation risk and food intake. Stephens and Krebs's (1986) Foraging Theory synthesized the field. Gould and Lewontin (1979) criticized the adaptationist program of treating every trait as an optimal adaptation, and Pierce and Ollason (1987) questioned whether optimal foraging theory is testable. Defenders reply that working out why a model fails reveals new constraints. The theory has been extended to anthropology to analyze hunter-gatherer societies (Smith, 1983), and Pirolli and Card (1999) proposed information foraging theory, explaining how people search for information on the web using the same principles. It is closely linked to other frameworks of evolutionary optimization such as game theory and life history theory.

FAQ

What is optimal foraging theory in simple terms?

It holds that animals have evolved to search for food in ways that yield the most energy for the time and effort spent, and it predicts this behavior with mathematical models.

What is the marginal value theorem?

It states that when the food gained in a patch steadily declines, an animal should move on once its current rate of gain falls to the average rate for the environment.

Sources reviewed: 2026-10-26

References

1. MacArthur, R. H., & Pianka, E. R. (1966). On optimal use of a patchy environment. American Naturalist, 100(916), 603–609.
2. Emlen, J. M. (1966). The role of time and energy in food preference. American Naturalist, 100(916), 611–617.
3. Charnov, E. L. (1976). Optimal foraging, the marginal value theorem. Theoretical Population Biology, 9(2), 129–136.
4. Krebs, J. R., Erichsen, J. T., Webber, M. I., & Charnov, E. L. (1977). Optimal prey selection in the great tit (Parus major). Animal Behaviour, 25, 30–38.
5. Pyke, G. H., Pulliam, H. R., & Charnov, E. L. (1977). Optimal foraging: A selective review of theory and tests. Quarterly Review of Biology, 52(2), 137–154.
6. Cowie, R. J. (1977). Optimal foraging in great tits (Parus major). Nature, 268(5616), 137–139.
7. Caraco, T., Martindale, S., & Whittam, T. S. (1980). An empirical demonstration of risk-sensitive foraging preferences. Animal Behaviour, 28(3), 820–830.
8. Gould, S. J., & Lewontin, R. C. (1979). The spandrels of San Marco and the Panglossian paradigm: A critique of the adaptationist programme. Proceedings of the Royal Society B, 205(1161), 581–598.
9. Pierce, G. J., & Ollason, J. G. (1987). Eight reasons why optimal foraging theory is a complete waste of time. Oikos, 49(1), 111–118.
10. Stephens, D. W., & Krebs, J. R. (1986). Foraging Theory. Princeton: Princeton University Press.
11. Lima, S. L., & Dill, L. M. (1990). Behavioral decisions made under the risk of predation: A review and prospectus. Canadian Journal of Zoology, 68(4), 619–640.
12. Smith, E. A. (1983). Anthropological applications of optimal foraging theory: A critical review. Current Anthropology, 24(5), 625–651.
13. Pirolli, P., & Card, S. (1999). Information foraging. Psychological Review, 106(4), 643–675.