Social Behaviour - Group Organisation Flashcards
What is social dominance?
When a group is characterised by aggresive/submissive relationships
Can result in ranking of individuals
How are hormones thought to be linked to dominance?
Low dominance = high levels of glucocorticoid (stress) hormones
Low rank = stressful
In baboons studies have shown that glucocorticoid levels increase in response to losing to subordinates but there is little change when losing to higher ranked individuals.
Battling way up appears to be less stressful than losing rank
Why are dominance and resource access linked?
Dominance = better access to food and/or mates
Often occurs at crucial points
Dominant females - mature earlier, produce more young and nurture mor effectively
Can result in a reproductive skew = unevenness
in distribution of reproduction among breeding individuals
Can lead to delayed reproduction
What are family groups?
Many species (mammal and bird in particular) live in multigenerational groups
Offspring interact with parents into adulthood
Occurs when young do not disperse from their natal area
- shortage of breeding sites
- natal area high quality
Can result in cooperative breeding where offspring receive care from parent but also helpers
What are the consequences of family groups and give an example
Relatedness among group members increases - kin selection and altruism
Offspring inherit breeding position of parents
Offspring acquire part of the natal territory
Clownfish - groups of breeding pairs plus 0-4 non-breeders
- non breeders gain neither present direct or nondirect benefits
- more likely to inherit the territory though
What are family heirarchies and give an example
Ranking by matrilnes and not individual competitive abilities
Spotted hyenas form stable heirarchies
Daughters rank directly below mother in reverse order of age i.e. younger daughters rank highest
Potentially results from females protecting young at a very vulnerable stage in social development
What is eusociality?
Characterised by the division of labour based on a caste system
- some members lose reproductive ability and become sterile workers
- others remain as reproductive individuals (kings and queens)
- cooperation in care of young
- maintenance of two overlapping generations
Give an example of eusociality in insects?
Termites
Live in nests or colonies
Hundreds, thousands, millions of indivduals
3 main castes - reroductive, workers and soldiers
Give an example of eusociality in mammals
Naked mole rats - native to E.Africa
75-80 indvs. living in complex burrow systems 3-5km in length
One female queen, 1 to 3 males reproduce rest of colony act as workers
What are the two hypotheses for the evolution of cooperation?
Indirect - altruistic cooperation - kin selection
Direct - mutually beneficial cooperation - mutualisms
What are the mechanisms for kin discrimination?
Location/Timing - relatives reliably associated with particular loacation
- Treat these individuals as kin?
- Male house mice often kill unrelated pubs but less likely in nests where previous copulation with a female
Familiarity - Learning during a critical period
- considered that voles use familiarity to assess kin
- familiar indvs. engage in less aggressive behaviours
Phenotype matching - discriminating without prior experience
- compare appearance through sound or odour cures
- phenotype exposure of Belding’s ground squirrels determined discrimination later in life
What is reciprocity?
Process by which cooperation might evolve
Relies on the likelihood that helpful acts will be repaid by the recipient at a later date
Benefit of the act must be greater to the recipient than to the cost of the actor
But temptation to cheat and defect is an ever present problem
What is reciprocal altruism and give an example
Behaviour whereby an organism acts in a way that temporarily reduces its fitness with the expectation that the other organism will do the same at a later time
Vampire bats - feed each other by regurgitating blood
- will die after 70hrs of not eating
- food sharing is of great benefit to the reciever
- great cost to donor
What is the prisoner’s dilemma?
Game theory approach
- Both keep quiet and don’t snitch (cooperate) only receive 1 year in jail each
- Both blame each other (defect) both receive 3 years in jail
- 1 blames the other but the other stays quiet the defector goes free, loyal friend gets 5 years
Both better off to cooperate than both defect but temptation to cheat and go free is ever present
What are the main differences in individuals within groups?
Sex Age Spatial position - centre/edge Social status - dominant/submissive Producer-scrounger relationships
