SI6- Social behaviour

• Many animals live in social groups and have behaviours that are adapted to group living such as social hierarchy, co-operative hunting and social defence.
• Social hierarchy is a system which establishes a rank order within a group of animals.
• In a social hierarchy, dominant individuals of higher rank carry out ritualistic (threat) displays while 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 is where animals hunt in a group
• Co-operative hunting enables larger prey to be caught and increases the chance of hunting success
• In co-operative hunting less energy is used per individual than when hunting alone.
• Co-operative hunting may benefit subordinate animals as well as dominant ones, as they gain more food than by foraging alone.
• An altruistic behaviour harms the donor individual but benefits the individual

  eg. alarm calls of vervet monkey
• Reciprocal altruism, where the roles of donor and recipient later reverse, often occurs in social animals

  eg. blood meals of vampire bats
• Behaviour that appears to be altruistic can be common between a donor and a recipient if they are related (kin)
• Kin selection favours the reproductive success of an organisms relatives at a cost to the organism's own survival and reproduction.
• 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 live in colonies where different types of adults play different roles (caste system)
• Reproduction and survival depend on all members of the colony working together
• Social insects include: ants, bees, wasps, and termites.
• Social insects have a society in which only some individuals- queen (female) and drones (male) contribute reproductively
• Most members of the colony are sterile workers who cooperate with close relatives to raise relatives
• Sterile workers care for the queen's offspring to increase the survival chances of shared genes (kin selection)
• Other examples of workers roles include:

  • defending the hive
  • collecting pollen
  • carrying out waggle dances to show the direction of food
• The primate group includes lemurs, monkeys, apes and humans
• Primates have a long period of parental care to allow learning of complex social behaviour
• Most primates live in social groups where there is competition for resources, so conflict can arise
• Primates exhibit a range of complex social behaviours which help to support the social structure of the group and reduce conflict
• Conflict (fighting) is reduced through ritualistic displays and appeasement behaviours
• Grooming, facial expressions, body posture, vocalisation and sexual presentation are part of ritualistic and appeasement behaviour
• Alliances form between individuals, which are often used to increase social status within the group
• Complex social behaviours support a social hierarchy with a rank order