Lecture 9 Optimal Foraging Theory

Optimal Foraging and Economic Decisions

• Optimal foraging: understanding how predators minimize costs and maximize benefits in their search for prey.

• Costs considered: time, energy, and prey abundance in environment.

Key Concepts

Foraging Behaviors

• Foraging behaviors can be analyzed using principles from microeconomics:

  • Costs and benefits determine optimal strategies in foraging, similar to economic decision-making.

  • The logic can also apply to other behaviors, such as mating.

• Competition may shift the costs and benefits of foraging strategies.

Predator Decision Making

• As predators search for food:

  • They sequentially encounter potential prey.

  • Decisions involve whether to pursue prey or continue searching, impacting time and energy costs.

• Each choice has potential costs (time, energy) and benefits (food intake).

Balancing Costs and Benefits

Mathematical Tools in Optimal Foraging Theory

• Animals as decision-makers aiming to maximize returns from foraging:

  • Currency/Payoff: energy, time, fitness.

  • Constraints: prey availability, time to locate prey, prey size.

  • Decision Variables: whether to pursue a specific prey type (generalist vs specialist).

Managing Diet Breadth

• Energy optimization through diet breadth - managing the diversity of prey types consumed:

  • Time wasted on difficult-to-catch prey could be better spent on easier options.

  • Assumptions about species abundance impact decision making:

    • Predators prefer abundant and easily consumable prey.

    • Introducing new prey types can increase time to capture.

Environmental Variation Effects

Optimal Diet Breadth in Different Habitats

• Comparison of predator populations in habitats with varying prey abundance:

  • An abundant habitat decreases average search time, leading to a narrower optimal diet breadth.

  • Predators develop specialized diets in more productive habitats (more efficient foraging).

Central Place Foraging

Resource Distribution

• Resources are patchily distributed, requiring movement between patches for foraging:

  • Predators must strategize to maximize food intake over time.

  • Importance of weighing time spent in a patch against potential resource depletion.

Giving Up Time (GUT)

• The optimal time spent foraging in a patch based on expected travel time to another patch:

  • GUT identified where a tangent line from travel time intersects with the gain curve for maximum benefit.

The Marginal Value Theorem

Resource Intake Over Time

• Balancing between visiting multiple patches and the time/energy spent moving:

  • An intermediate amount of time spent in patches optimizes resource intake.

• Cumulative resource intake depicted against time spent in patches illustrates diminishing returns.

Game Theory in Behavioral Ecology

Hawk-Dove Game

• Strategies based on competition between aggressive (hawks) and passive (doves) behaviors:

  • Hawks always win against doves but risk injury against other hawks.

  • Doves avoid injury by not fighting.

Payoffs and Strategy Selection

• Average payoff calculations involve benefits and costs:

  • Payoffs are strategic based on opponent's action (hawk or dove).

• High payoff strategies depend on the opponent's strategy, creating a dynamic interplay within populations.

Population Dynamics

• The presence of both hawks and doves can be stabilized by natural selection:

  • Population frequencies of strategies can lead to coexistence, even in seemingly competitive situations.