A graphical representation of the marginal value theorem.

A graphical representation of the marginal value theorem. The x-axis represents the total time spent foraging, which includes both travel to a patch and time spent in a patch. The y-axis represent the total amount of energy gained by the organism as a function of time spent foraging. (a) The rate of energy gain can be calculated as the slope of G/T. This value is maximized at the point where a line drawn from the origin is tangential to the gain curve. The optimal time to spend in the patch is determined by the value of the x-axis directly below the point of intersection. (b) Here we see two possible scenarios, short travel times (purple) and longer travel time (red). The optimal foraging strategy is to spend less time in a single patch when travel times are shorter.