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8 -- Socio biology - Agression - Coggle Diagram
8 -- Socio biology - Agression
defintions
aggression varies widely in form and function
Tinbergen (1973) - any behaviour which tends to remove an opponent or make it change its behaviour such that it no longer interferes with the attacker
Moyer (1968) - behaviour that leads to, or appears to lead to the damage or destruction of some goal entity.
Moyers is widely used but is too limited as aggression doesn't always involve damage or destruction. Tinbergen's is more flexible.
over 100 published
types
Moyer (1968)
lots of classification systems with up to 8 sub types
John Archer (1988) functional classification scheme
protective aggression (threat to self, escape, attacks damaging) - may be lethal as it is self defence
Parental aggression (threat to offspring, attacks potentially lethal) - potentially lethal as mother protecting babies
competitive aggression (predom male, hormonal, seasonal) - not lethal as only to protect land
fighting
why animals fight?
direct consequence of sexual reproduction and generation of genetically distinct individuals
self vs others
resource competition
competition for limited resources that are vital to fitness
all species that can fight, do fight
Sea anemones
fight for food resources
Humans
fight for women
competition
Scramble competition = accumulation of resources (no social interaction)
Contest competition = active conflict (for resources related to fitness) aggression is the main mechanism.
aggression is adaptive
social stability
social disorganisation = high levels of aggression - human interference with ecosystem or dominant is removed in initial group formation
associated with low levels of aggression - established dominance hierachies
when to be aggressive?
expect to see fighting or results of previous fighting when competition enhances fitness
no point in fighting when
lack physical maturity
lack experience
nothing to be gained and a lot to loose
socially - subordinate
no need to fight when
resources are abundant
low population density
factors
Sleeping areas (E African baboons - fight for rocky edges to sleep to avoid being hunted by lions)
Territory (fur seals, penguins - males fight for best spot for their females and babies)
food (Rhesus monkeys - monks feed the local monkeys in temple grounds causing aggression due to unfair distribution)
Nest sites (Kittiwakes - birds nest on steep cliffs and fight for best spot)
access to mates
sex differences
proximate explanation = testosterone
Ultimate explanation = F are a vital resource for M leading to intergroup competition
aggression is usually sexually-dimorphic = M > F
Females should be aggressive when need to defend young or when going to be killed
Barash 1982
Theoretical view
benefits = access to resources
costs = time and energy, injury, predation
His theory predicts that fighting should escalate only to a point of maximum difference between the costs and benefits
selection then should favour the optimum not maximum level of aggression
is it supported?
Ultimate explanation
animals that can get resources without fighting are fitter than rivals (cost benefit analysis)
selection favours evolution of mutually accepted rules of combat
aggression linked to ritualised tournaments
proximate explanation
animals have elaborate behaviours that allow resolution of conflict without using violence
threat displays (yawn threat male baboons)
ritualised attacks (damaging non vulnerable parts of the body - elephant seals)
trials of strength (antler fights in stags)
Signals of submission (dogs baring their vulnerable ventral surface to opponents)
field studies with many species confirm the rarity of fatalities in intraspecific competition
requirements
effective communication
Unambigiuous signals of submission (defeat postures, gaze aversion, appeasement gestures)
unambiguous signals of aggressive competence (exaggerated weaponry, vivid threat displays)
Victory and defeat create physiological changes (hormones) - victory (testosterone) defeat (cortisol)
unambiguous signalling
Mandrill
Baboon
Red deer
wolf