Social Relationships Flashcards
Why live in groups?
Resources
Predation
Ecology
How do resources contribute to group living?
Communal roosting e.g. bats, cooperative hunting, aggregated resources e.g. birds
How does predation contribute to group living?
Reduced vigilance = foraging
Dilution
Confusion
Communal defence
What affects optimal group size? What does the graph look like?
Competition - increases linearly with group size
Predation risk - decreases with group size
Produces fitness bell curve
so optimal is in middle (i.e. top of bell curve)
When do dominance heirarchies occur?
Where individuals can monopolise resources, strongest do the best
When do we see egalitarian groups?
Where monopoly cannot occur e.g. dispersed resources
Sapolski’s baboons?
Social system: higher ranked were healthier, lower ranked showing high stress hormone volumes, heart rates and blood pressure
When the dominant males died due to poisoned food, the social structure became less aggressive and lost their health disparities
Hormones in baboon social groups? (2)
Testosterone - declines with rank
Glucocorticoids - increased in lower ranks, giving suppressed immune and reproductive function
Social insecurity in baboons?
Mid-ranks may have authority questioned - they, along with low ranks, must suppress aggression to avoid health defects
Social insecurity in macaques?
Opposite - mid-ranks had highest stress because of this insecurity, due to the system as a whole being less aggressive so low ranks not as affected.
Social Bonds
May convey fitness benefits e.g. in horses - those with more friends had higher reproductive rates
Reproductive Suppression
Occurs in cooperative breeders; males and females who help may have dampened reproductive ability
Hormones in breeding females?
Increased oestrogen and prolactin
Hormones in breeding males?
Increased GCs and testosterone
Reproductive Cessation
Menopause - only really evident in humans, orcas and elephants
