conflict resolution threat-display contests –hawk-dove-bully –hawk-dove-assessor variable length...
Post on 19-Dec-2015
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Conflict Resolution
• Threat-display contests– Hawk-dove-bully– Hawk-dove-assessor
• Variable length contests– War-of-attrition– Sequential assessment
• Variable sequence contests
Dove-Bully GameOpponent: Bully Dove
Actor: BullyDove
V/2 V 0 V/2
Opponent: Bully Dove
Actor: Bully 1 2Dove 0 1
If V = 2 then
Bully is a pure ESS
Hawk-Bully GameOpponent: Bully Hawk
Actor: BullyHawk
Opponent: Bully Hawk
Actor: Bully 1 0Hawk 2 -1
If V = 2, C = 4 then
Yes, Hawks can invade Bullies, but Bullies invade HawksTherefore, this is a mixed ESS
V/2 0 V (V-C)/2
Correlated asymmetry• Opponents differ in RHP• Example: hawk - dove - assessor
– Assessor strategy: if larger play hawk, if smaller play dove
– If owner and intruder are equally frequent and get equal payoffs:
Opponent: Hawk Dove Assessor
Actor: HawkDoveAssessor
(V-C)/2 V (V-C)/2 0 V/2 V/4 V/2 3V/4 V/2
When there is a cost to fighting, Assessor is pure ESSassuming that assessment is costless and accurate
Calling in toads
War of attrition - the waiting game• Assumptions
– Resource cannot be shared– Cost of display increases with length of contest– No information is received during contest and
opponents are symmetrical– Winner is the contestant willing to accept the
higher cost– The cost to both contestants equals the cost
acceptable to the loser– The range of actions of each contestant is
continuous
War of attrition - Payoff matrixxi = amount of time individual i displaysk = rate at which costs are expendedV = value of resource
Payoff to: Player A Player B
Actor : xA > xB
Opponent: xA < xB
V - kxB - kxB
- kxA V - kxA
No pure ESS is possible, since an opponent that displayed a littlebit longer would have higher fitnessSolution is a mixed ESS where the probability of leaving at anytime is a constant. The times an individual stays should bedistributed as a negative exponential.
Asymmetric war-of-attrition
• If animals experience different costs of display or the resource differs in value to them, the game is asymmetric
• Which player has the largest V/k will win, but this may not be known
• This may lead to two different giving up time strategies
War-of-attrition solutions
Fight duration and resource value in newts
Males fight longer overlarger females. Largerfemales carry more eggs and are, therefore, morevaluable.
Sequential assessment
• Assumptions– Animals display in order to acquire information about
each other’s fighting ability and resource value
– Fights only occur when animals are closely matched
• Predictions– Fight duration increases as the asymmetry in fighting
ability decreases and/or as resource value increases
– The cost of a fight increases as the asymmetry in fighting ability decreases
– Probability of winning increases with asymmetry
Sequential assessment ESS
War of attrition in spiders
Resource value equal
Ownership effects in spider fights
War of attrition in spiders
Assessment in red deer
Jumping spider contest stages
Sequential assessment in phases
Sequential assessment in cichlids
Why give multiple signals?
• Each display serves a different function
• Signal erosion: threat displays lose effectiveness as the frequency of bluff increases
• Displays transmit graded information about display intentions– Multiple signals may lower potential risk
associated with escalation
Cricket display costs
Little blue penguin fights
Cave dwellers use more displays, but have lower escalated fights
Little blue penguin display repertoire