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Living in Groups - Coggle Diagram

- - - - Likely to vary with the size of the group
        
        OPTIMAL group size of a group is difficult to calculate due to the difficulty of measuring all costs and benefits
        
        New individuals (outsiders) continue to join the group so long as the benefits of living in the group outweigh the benefits of living alone
        
        This often results in group size exceeding the optimum fitness level
      - Costs
        
        Increased resource competition (food, mates. etc)
        
        foraging intake declines in groups through interference
        
        Kleptoparasitism
        
        time costs through aggression/ 'pseudointerference'
        
        Other foragers may trigger anti-predator responses
        
        e.g. prey is harder to catch when another predator has recently been in the habitat
        
        Interrupted matings. etc
        
        Increased conspicuousness to predators
        
        Increased rates of parasitism and disease
        
        the extent to which group size influences parasite load varied across species
      - Benefits
        
        Reduced predation
        
        Dilution effect
        
        May explain other unusual grouping behaviours
        
        Predator swamping
        
        Acceptance of other female's young
        
        Kidnapping
        
        Helps to reduce the 'domain of danger'
        
        Selfish Herd Effect
        
        Moving closer to another will reduce the domain of danger
        
        Improved vigilance
        
        Many eyes hypothesis
        
        Communal defence (e.g. mobbing predators
        
        Predator confusion
        
        Enhanced foraging
        
        Improved food capture (e.g. group hunting)
        
        Improved information (can be inadvertent or active)
        
        Improved mate choice
        
        Improved thermoregulation
        
        Improved movement
        
        E.g. flying in a 'V' formation reduced energy expenditure compared to flying alone
        
        Territorial defence
        
        Cooperative care of young
        
        Building structure with bodies in social insects
- - - - Costs and benefits are also likely to differ within groups, between group members/ individuals depending on their ability to compete for essential resources - resulting in conflict over what the optimal group size is
        
        How to groups remain stable despite this conflict?
        
        Individual vs. group selection
        
        Group selection = behaviours can be selected for if they are 'for the good of the group'
        
        Selection on individuals = likely to be far stronger, as individuals die out faster than groups, allowing for a much faster rate of reproduction and turnover
        
        Similar to the way that the rate of evolution is often faster in species with shorter lifespans compared to long-lived species
        
        Understanding behaviours in groups relies on understanding selection pressures on individuals and their genes
        
        In some societies, this competition over resources can result in social structures (i.e. DOMINANCE HIERARCHIES)
        
        In these social structures, costs and benefits of group living are likely to vary with social rank (i.e. dominants take a greater share of the benefits
    - - REPRODUCTIVE SKEW THEORY
        
        Reproductive success varies across group members.
        
        humans have a low reproductive skew as most are able to breed in their lifetime
        
        In other species (e.g. naked mole rates, eusocial insects. etc) reproductive skew is much higher due to the long lifespan of the dominant individuals or sterility of subirdinate individuals
        
        Dominant control of reprodution
        
        Control
        
        Eviction
        
        Aggression leading to stress levels which may result in infertility due to hormone imbalances
        
        Threats/ empty threats
        
        Infanticide/ egg-eating/ throwing eggs out of the nest
        
        Exclusion/ punishment
        
        Physical damage of reproductive systems
        
        In most cases, dominants do NOT have complete control over subordinate reproduction
        
        Evasion
        
        Challenging in case they are empty threats
        
        synchronised birth with dominant
        
        strategic distraction
        
        paternity confusion
        
        Disrupt dominant breeding attempts
        
        Different morphs (e.g. some male morphs looking like/ mimicking females to avoid detection when mating)
        
        Sneak offspring into the dominant females nest
        
        Giving birth away from the group
        
        Scrambling odour cues
        
        Females can form alliances with males to protect themselves from attacks from higher ranking females
    - - In some cases, the threat of punishment may be enough to maintain group stability, even in the absence of overt dominant control