Behavioral Ecology: Problems 2

Problem :

In a hawk-dove game, if the benefit of winning is 10 and the cost of losing is 7, what is the best strategy to play, hawk or dove?

In contests modeled after the hawk-dove game, when the benefit is greater than the cost, the best strategy is to always play hawk.

Problem :

If the Prisoner's Dilemma game is repeated multiple times, why should you not always cheat?

Figure %: Payoff Matrix for the Prisoner's Dilemma

The Prisoner's Dilemma, when repeated, offers a maximum reward if you mix up your strategy. It is true that cheating offers a better reward no matter what your opponent does, however, by mimicking your partner's behavior, you will obtain the maximum reward. When your partner cheats, you should cheat in the next game. When your partner cooperates, you should cooperate in the next game.

Problem :

Consider two breeding strategies of the fictional Woozle. Dominator Woozles can fight for a breeding territory, and if they win, will be able to rear 10 offspring. An alternative is to share territory with another Woozle which will allow each to rear 5 offspring. Sharers who attempt to share with dominators will be forced out of the territory, although they will be able to find a new territory. Assume sharers become extra catious after encountering a dominator and so will always find another territory to share the next time around, but due to lost time will only be able to produce 3 offspring. Dominators are always able to force sharers out of the territory and rear 10 young. Dominators who meet dominators will win 50% of the time. When they lose, they are not able to reproduce that season due to sustained injuries. Individual Woozles cannot switch strategies. What proportion of the population would you expect to be dominators, and what proportion would be sharers?

Figure %: Payoff Matrix for Woozle Mating Strategies

If a dominator meets another dominator, he has a 50% chance of winning and producing 10 offspring, and a 50% chance of losing which means a cost of 10 offspring. Therefore the average payoff for a dominator/dominator encounter is zero. Dominators who meet sharers will win the territory and produce 10 offspring. Sharers who meet sharers will produce 5 offspring each. Sharers who meet dominators will always produce 3 offspring at their new territory. Since these are the only two mating strategies Woozles can choose from, we know that the proportion of dominators (p) and sharers (q) will equal the entire population. We then use our equations to estimate the relative payoffs for the dominator strategy and the sharer strategy. We end up with the following two equations: p + q = 1
p(0) + q(10) = p(3) + q(5)
Solving for p and q yields:
p=5/8
q=3/8

5/8 of the population will be dominators and 3/8 will be sharers.