• Many animals live in social groups and have behaviours that are adapted to group living such as social hierarchy, cooperative hunting and social defence.

  • Social hierarchy is a rank order within a group of animals consisting of a dominant and subordinate members. 

  • In a social hierarchy, dominant individuals carry out ritualistic (threat) displays whilst subordinate animals carry out appeasement behaviour to reduce conflict.

  • Social hierarchies increase the chances of the dominant animal’s favourable genes being passed on to offspring. 

  • Animals often form alliances in social hierarchies to increase their social status within the group.

• Co-operative hunting may benefit subordinate animals as well as dominant ones, as they may gain more food than by foraging alone. 

• Less energy is used per individual. 

• Co-operative hunting enables larger prey to be caught and increases the chance of success.

• Social defence strategies increase the chance of survival as some individuals can watch for predators whilst others can forage for food. 

• Groups adopt specialised formations when under attack protecting their young.

Altruism and kin selection and its influence on survival.

• An altruistic behaviour harms the donor individual but benefits the recipient.

  • Reciprocal altruism, where the roles of donor and recipient later reverse, often occurs in social animals.

  • The prisoner’s dilemma as a simple model of altruism.

• Behaviour that appears to be altruistic can be common between a donor and a recipient if they are related (kin).

• The donor will benefit in kin selection in terms of the increased chances of survival of shared genes in the recipient’s offspring or future offspring.

• Social insects and the structure of their society in which only some individuals (queens and drones) contribute reproductively. 

  • Social insects include bees, wasps, ants and termites.

• Most members of the colony are sterile workers who co-operate with close relatives to raise relatives.

  • Other examples of workers’ roles include defending the hive, collecting pollen and carrying out waggle dances to show the direction of food.

  • Sterile workers raise relatives to increase survival of shared genes.

Primate behaviour

• Primates have a long period of parental care to allow learning of complex social behaviour.

• Complex social behaviours support the social hierarchy. 

  • Grooming, facial expression, body posture and sexual presentation.

• This reduces conflict through ritualistic display and appeasement behaviour.

• Alliances form between individuals, which are often used to increase social status within the group.