1. Fighting ‘rules’
Assessment and possible escalation

2. Degree of escalation depends on resource value

3. Value of resource Elephant seal Red deer Rep at age 9-12
10% reach rep. age
Up to 93 pups sired per year but only 9% of males mated
Fights typically escalate to injury
Rep from ages 6-12
75% reach rep. age
2-4 calves sired per year
Fights typically do not
have serious injuries

4. Weapons usually not fatal
Fighting is highly ritualized

5. To escalate and fight or not??
There often is not always one optimum behavior in a population – what works might depend on what others do.

6. Why don’t fights escalate to lethal fights?
“Hawk-like tactic” vs. “Dove-like tactic”
Fight and risk injury
Display and don’t escalate

7. Costs and benefits:
Access to resource (V) if you win
Fighting incurs costs (C) of injury

8. Outcome of interactions:
Hawk and Hawk:
Dove and Hawk:
Dove and Dove:

9. If: V = 50 , C= -100 What if all are doves? What if all are hawks?
Opponent
Hawk Dove
Attacker
50 + (-100)
= -25
Hawk
Dove 50 50 2
= 25
What if all are doves?
What if all are hawks?

10. Dove avg. payoff = Hawk avg. payoff
So in this scenario, you would expect some sort of mixture of hawks and doves. (A mixed ESS) You can calculate the exact mixture -
When:
Dove avg. payoff = Hawk avg. payoff
Payoffs depend on proportion of hawks and doves

11. Proportion of hawks = h
Proportion of doves = (1-h)
Hawk avg. payoff:
H = -25h + 50(1-h)
Dove avg. payoff:
D = 0h + 25(1-h)

12. -25h h = h
50h = 25
h= ½
50% hawks, 50% doves is the mixed evolutionary stable strategy in this case only

13. “Evolutionary stable strategy” - (ESS)
Tactic or combination of tactics (like 50/50 hawks/doves) that resists “invasion” by individuals using any of the known tactics.
Note that an ESS does not have to be a mixed ESS.

14. Assumptions of ESS approach:
Reproduction occurs in proportion to fitness gained relative to V and C. (p.117)
Random mixing of strategies in pop’n

15. Recall this : amount of escalation depends on the value (V) of the resource. V<C is generally seen in nature, but there are cases where V is very high…or where low expected future RS
p. 118

16. ‘Bully’ tactic – if it meets a dove, acts like a hawk; if it meets a hawk, acts like a dove.
If this ‘invaded’, new ESS would be 100% Bully
Hawk Dove Bully
-25 50 25
Hawk
Dove
Bully

17. Can mixed ESS occur in nature?
Maintenance of different tactics within populations
Ex: Natterjack toads
Callers get 80% of matings overall
Satellites gain 50% of females attracted by call
Males have conditional strategy with 2 ‘tactics’
Tactics here are flexible - tactic chosen depends on situation, male size
Ex: Manipulations with broadcasted calls

18. Predicting tactics

19. Mixed ESS or ‘best of a bad job’?
Satellite males – “best of a bad job”
similar to ‘scroungers’ in text example
Mixed ESS with
Best of a bad job frequency dependent selection
p. 130

20. Strategy vs Tactic
Strategy – genetically based. Can be conditional with different tactics
ex: conditional strategy
ex: size sets the tactic
Tactics – specific behavior patterns that are part of a strategy, one usually better
ex: call when big, satellite when small

21. Alternative tactics But some tactics may be fixed for lifetime
Bearded weevils – some small males 10% normal size, sneak matings
Male bedbugs – traumatic insemination, small males alternative
Is this mixed ESS or BOBJ?
But some tactics may be fixed for lifetime

22. Alternative tactics But some tactics may be fixed for lifetime
Dung beetles:
Morphological development
and body size
p. 134

23. Alternative strategies: mixed ESS
Different genetic forms that are maintained in a population (more than 1 strategy in pop’n)
Payoffs would be about equal on average, like a mixed ESS
Frequency dependent selection

24. Alternative strategies with mixed ESS
Ruffs - male dimorphism – three strategies:
- Red residents (~30% of males) 90% of copulations, poorer survival
Black ‘marginals’ (floaters, but future residents) (~50%)
- White satellite (~20% of males) only 10% of copulations
Satellites live longer, free for forage, find off-lek females
- Female mimics (1%)
p. 139

25. Alternative strategies with mixed ESS
Marine isopods – 80% are α males that defend harems (20% of size=testes)
4% are β female mimics (50% testes)
15% are γ tiny males with 80% testes
Study examining genetic RS found success was equal among types and varied w/# females, # morphs.

26. Alternative strategies with mixed ESS
Side-blotched lizard: 3 male strategies
Orange – high testosterone territory holders
Yellow – sneaker female mimics at territory edges
Blue – defend one female, can drive away yellow males but not orange
Again, success of each strategy depends on frequency of others

27. Animal personalities?
Mixed ESS and ‘best of a bad job’ show how different behavioral tactics can persist in populations.
When are differences in behavior discrete ‘tactics’ ..can there simply be personality differences?...are they genetic?

28. Parus major personalities
Exploratory behavior – consistent and inheritable
Two selection lines formed – genetic basis
How do these differences persist?
Personalities and life history traits