marginal value theorem A mathematical rule, proposed by E. L. Charnov in 1976, according to which the optimum time a foraging animal remains in a patch is defined in terms of the rate at which the forager is extracting energy at the time it leaves (the marginal value of the patch). The optimum foraging strategy is to abandon each patch when the rate of energy extraction from it falls to a certain level, this level being the same for all patches. The theorem predicts that foragers will remain a shorter time in patches with little food than in patches with more food, patches will be abandoned more quickly when they are close together than when they are scattered, and patches will be abandoned more quickly in an area of abundance than in a poorer area.

marginal value theorem A mathematical rule, proposed by E. L. Charnov in 1976, according to which the optimum time a foraging animal remains in a patch is defined in terms of the rate at which the forager is extracting energy at the time it leaves (the marginal value of the patch). The optimum foraging strategy is to abandon each patch when the rate of energy extraction from it falls to a certain level, this level being the same for all patches. The theorem predicts that foragers will remain a shorter time in patches with little food than in patches with more food, patches will be abandoned more quickly when they are close together than when they are scattered, and patches will be abandoned more quickly in an area of abundance than in a poorer area.