Section 3: Predation (part B), Herbivory, parasitism, popn. Regulation, biocontrol, fisheries, conservation biology.

PREDATION… Continued (Part B)

C. Studying predator effects on prey populations in the field.

1. Manipulative experiments

2. Accidental Experiments

3. Comparative Studies- woodland caribou
-Food limited
-Predator limited

D. Optimal Foraging theory: how do predators choose their diets? (see chapter 3)

*What is the optimum strategy? = Energy maximization or time minimization Max En/T

Assumptions about the predator (forager): -Eating and searching for the next food (prey) item are mutually exclusive activities. -Items are found sequentially, items are found one at a time.

Energetic Value of prey: EACH PREY ITEM HAS AN ENERGENTIC VALUE (ei)

Handling time: A HANDLING TIME (hi)

Profitability:
: e/h= profitability of each prey item (such that prey can be ranked)

Rule: optimal foraging rule (prediction) – always eat the most profitable prey and eat the next most profitable prey if the gain is greater than the gain from rejecting it and searching for a more profitable prey.

Predictions of Optimal Foraging Theory: The highest ranked prey type should always be eaten when encountered.

1) Predators with small handling times and long search times should be GENERALISTS.

2) Diets should be broad in pre-poor (unproductivr) environments.

3) The abundance of low ranking prey types is unaffected by the a abundance of the low-ranking prey is irrelevant.

Herbivory and mutualisms (Chapter 12)

A. Introduction
-Herb ivory: animals feeding on plants.
-Only part of the prey item is eaten base of many food webs

B. The world is green.

Thus, herbivores cannot consume all of the available plants

Explanations: -Herbivores may be self- regulated