Foraging has long been studied with the underlying assumption of optimal foraging theory, which states that a foraging animal will try to maximize its energy intake. Thus, foraging behaviour can be described using two simple models: the prey choice model, and the marginal value theorem. The prey choice model has three elements: caloric value of a prey item (E), handling time (h), and search time (S). Profitability is the rate of energy intake for a prey item: Eh. There are two canonical prey item types, prey type 1 and prey type 2, the former has the highest profitability and the latter has the lowest profitability such that:
E1/h1>E2/h2
Therefore, the only time a predator should eat prey type 2 is when:
E2/h2>E1/(h1+S1)
This yields three predictions: the animal will always try to maximize caloric intake; the animal will instantly shift to the less profitable prey type once the inequality is met; and S2 will not affect the animal’s choice to eat prey type 2. The marginal value theorem is a description of the movement of an animal from one patch to the next. This is a graphical model that describes the optimal amount of time the animal will spend in a patch. The cumulative energy gain in a given patch will increase rapidly and then level off, the tangent to that curve from the point indicating the animal’s travel time gives an optimal point at which the animal should leave the patch to maximize caloric intake.
Recent comments