Biology 338: Lecture 18Spring 1997

Living in Groups

  1. Costs
    1. Automatic
      1. Increased competition
      2. Increased probability of parasite/disease transmission
    2. Non-automatic
      1. Increased conspicuousness to predators
      2. Increased conspicuousness to prey
      3. Increased probability of caring for unrelated young
      4. Increased probability of infanticide
      5. Increased probability of inbreeding
      6. Increased indirect interference

  2. Benefits
    1. Decreased probability of predation
      1. Quicker predator detection
      2. Active group defense
      3. "Selfish herd"/center vs. edge effects
      4. Dilution effect/safety in numbers
      5. Confusion effects
    2. Decreased probability of going hungry
      1. Coordinated group attacks
      2. Group defense of food "bonanza"
      3. Locating patchy, unpredictably distributed prey

  3. Forced group living due to lack of suitable habitat