Optimal Foraging Behavior  Species should forage in an efficient manner that maximizes benefits and minimizes costs  Varies with species and environmental context  MacAuthur 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

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  E i /h i  Where E i = energy (caloric) content of a new diet item and h i = 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 E i /h i > 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  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