Behavioral Ecology and Adaptive Behavior

Behavioral Ecology and Infanticide in Lion Packs

Infanticide in Lion Packs: A Case Study

  • Lions live in social structures known as prides.

  • Adult female lions within a pride tend to be closely related.

  • Young adult male lions often form groups referred to as "bachelor prides."

  • At the age of 4 or 5 years, male lions may challenge the dominant adult males in the pride.

    • If a young male successfully takes over a pride, he often kills the cubs present.

    • This behavior may seem aggressive, but it is considered adaptive for several reasons:

    • Increase reproductive success: By eliminating the cubs of the previous male, he increases the chances of his genes being passed on.

Key Concepts in Behavioral Ecology

8.1 Evolution is the Basis for Adaptive Behavior

  • Learning Objectives:

    • Explain how natural selection can lead to the evolution of adaptive behaviors.

    • Illustrate the interaction between the environment and genetics in influencing behavior.

8.2 Behavioral Choices Enhance Energy Gain and Reduce Predation Risk

  • Learning Objectives:

    • Explain optimal foraging theory.

    • Relate optimal foraging, resource density, and the marginal value theorem.

8.3 Mating Behaviors: Balancing Costs and Benefits

  • Learning Objectives:

    • Describe animal behaviors used to access mates.

    • Evaluate the benefits of different sexual selection strategies.

8.4 Advantages and Disadvantages of Living in Groups

  • Learning Objectives:

    • Describe potential benefits and costs of living in groups.

    • Explain how individuals benefit from group living.

An Evolutionary Approach to Behavior

  • Behavioral Ecology:

    • Defined as the study of the ecological and evolutionary basis of animal behavior.

    • It considers two levels of behavioral explanation:

    1. Proximate causes: Refers to the immediate mechanisms that lead to behavior.

    2. Ultimate causes: Refers to the evolutionary and historical reasons why behavior occurs.

    • Behavioral ecologists primarily focus on ultimate causes.

  • If advantageous traits are heritable, natural selection promotes adaptive evolution in organisms.

Antipredator Behaviors

  • Include strategies by prey to:

    • Avoid being seen

    • Detect predators

    • Prevent attacks

    • Escape once attacked

Foraging Behavior

Optimal Foraging Theory

  • Proposition: Animals aim to maximize energy gain per unit time spent foraging, minimizing risks associated with finding food.

  • Assumes that evolution favors behaviors that maximize energy acquisition.

    • Animals waste time if unable to locate food efficiently.

  • Profitability of a food item (P) is calculated as:
    P = \frac{E}{t}
    Where:

    • E = energy gained from the food item (net energy).

    • t = time spent finding and obtaining the food.

  • Example: A study on the great tit and mealworms showed that selection for larger prey is significant as they require less travel time to find and consume.

Marginal Value Theorem

  • Formulated by Charnov (1976):

    • An animal should remain in a patch until the rate of energy gain declines to match the average rate of the entire habitat before moving to another patch (giving up time).

    • Factors influencing giving up time include:

    • Distance between patches

    • Energy density of food within patches.

Critiques of Optimal Foraging Theory

  • Optimal foraging may not be applicable for animals feeding on mobile prey due to the assumption that energy is the only resource needing maximization.

  • Variations in the environment (abundance of nutrients vs. sheer quantity) may also play a key role in foraging strategies.

Mating Behaviors

Parent Investment and Mate Defense

  • Mating behaviors often reflect the costs and benefits associated with parental investment.

  • Direct Benefits of Mating:

    • Males may offer nuptial gifts (e.g., food) or provide protection and help in rearing young.

  • Indirect Benefits:

    • In some species, males may not provide substantial resources, but females can gain indirect genetic benefits through offspring.

Sexual Selection Hypotheses

  1. Handicap Hypothesis: Males may carry costly traits (e.g., larger ornaments) signaling fitness and attracting females despite the associated risks.

  2. Sexy Son Hypothesis: Females may mate with attractive males, ensuring that their sons inherit these desirable traits, ultimately increasing their reproductive success.

Examples of Mating Systems

  • Monogamy: One male mates with one female for one or more breeding seasons.

  • Polygyny: One male mates with multiple females.

  • Polyandry: One female mates with multiple males.

  • Promiscuity: Both males and females have multiple partners.

Benefits and Costs of Group Living

Benefits:

  • Higher reproductive success due to access to high-quality territories.

  • Shared responsibilities in feeding and caregiving.

  • Reduced risk of predation through cooperative defense mechanisms (e.g., predator detection).

  • Prediction: The larger the group, the lesser the risk for each individual of being targeted by a predator (Dilution Effect).

Costs:

  • Increased competition for resources leading to potential food depletion.

  • More time required to move between feeding sites.

  • Higher likelihood of parasite and disease transmission due to closer contact in groups.

Summary of Key Concepts

  • An evolutionary perspective on behavior leads to testable predictions.

  • Animals exhibit behavioral choices that enhance their energy gain while minimizing predation risk.

  • Mating behaviors should be viewed through the lens of parental investment and mate defense.

  • Understanding the advantages and disadvantages of living in groups is vital for comprehending social dynamics within animal populations.