Optimal Foraging

Often in life, the things an individual needs may not be within immediate grasp. So, organisms need to forage. Foraging is defined simply as the process of searching for food or more generally resources. Although food is probably the first example that comes to mind, organisms must forage for other resources like shelter or mates and animals often go to great lengths to get what they need. However, the act of foraging itself requires energy. Essentially, individuals must balance burning calories with obtaining them. To put it simply, foraging requires a strategy. Ecologists created the optimal foraging theory to model the circumstances in which an organism meets the optimum balance between energy expended foraging, i.e., two acorn's worth and the potential energy it can acquire like six new acorns.

One characteristic of foraging is that resources are not always spread out evenly within a habitat. More typically, resources are contained in patches that foragers must move between. So how exactly should foragers navigate these patches of resources? In 1976, evolutionary ecologist Eric L. Charnov came up with the marginal value theorem or MVT to explain how organisms optimize their foraging. The MVT has five main predictions for optimal foraging. First, it states that foragers should capture more prey in patches with high prey density than in low prey density patches. Second, the theory predicts that foragers should spend more time hunting for resources in high prey density patches. Next, the forager should have a higher prey capture rate in dense environments with patches that are closely packed together than in sparse environments with patches that are spread further apart. The fourth prediction states that foragers will spend more time foraging in these dense environments than in sparse environments. Finally, a forager should leave a patch when the capture rate has declined to the average rate of all patches. And this is where a concept called giving up time or GUT comes in. To calculate the GUT simply subtract the time that the final prey item was acquired from the time that the individual leaves the patch. Therefore, the GUT should be the same for all of the patches a forager visits.

In this laboratory, you will complete foraging simulations in several different artificial resources patches and then perform calculations to gauge how your class performed as foragers and whether you adhered to the rules of the marginal value theorem.