Optimal Foraging Behavior Species should forage in an

Optimal Foraging Behavior Species should forage in an efficient manner that maximizes benefits and minimizes costs Varies with species and environmental context Mac. Authur and Pianka – optimal foraging theory

Optimal Foraging Theory Studied how long a predator will forage in a specific area Influence of prey density on the length of time a predator will forage in an area Influence of prey variety on a predator’s choice of acquired prey Main assumption: natural selection has operated strongly on foraging behavior, then foraging behavior should be adaptive. Used to generate models and predictions about foraging behavior

Optimal foraging models Attempt to predict the behavior of an animal while it searches for food, a nesting site, or other key niche components. Outcome of models predicts how individuals move in the environment and how individuals are distributed in the environment.

Real behavior vs. models When real foraging behavior differs from optimal behaviors it gives us clues to constraints either in the animals’ behavior or thinking or in the environment Once constraints are identified, behavior does approach optimal foraging pattern

Time = cost Calories = benefit

Marginal Value Theorem “giving up time” As an animal forages, the amount of energy gain gradually begins to slow down as food becomes scarcer in the patch Travel time governs decision

Ideal Free Distribution Patch quality and competition taken into account Animals will distribute themselves in the place where gains will be the highest At equilibrium, the number of competitors in each patch is proportional to the quality of the patch

Different versions of OFT Optimal diet model Patch selection theory Central place foraging theory

Optimal Diet model E/h where E = energy content of each item in the diet h = handling time (energy) required to capture, subdue, and consume each item Ei/hi Where Ei = energy (caloric) content of a new diet item and hi = handling time (or energy) required to capture, subdue and consume new prey item Is new diet more favorable than the old diet? Search time (More energy) E/(s + h) where s=average search time for old diet Diet should expand if Ei/hi > E/(s + h)

Central Place Foraging Theory Special case of the marginal value theorem Deals with animals that forage around a retreat site Deals with how much an animal will gather before returning to retreat Also with how best to exploit the resources around the retreat before moving on

Zach’s study of Northwestern Crows drop shellfish to break outer shell Experimenter dropped shells from different heights Determined the optimal height necessary to break shells Crows dropped shells at similar height

Sunfish Provided sunfish with prey of different sizes and densities Fish took most energetically rich prey under the appropriate conditions