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Game theory and Gouldian finch populations

An interesting application of game theory comes up in animal populations competing for limited resources. One particular instance is the balance of peaceful and aggressive members of Gouldian finch populations. These birds are born with a genetic predisposition to react to conflict in one of two ways. Peaceful black-headed finches, when faced with a conflict for some resource (perhaps a nesting space, or food), will typically choose to back off and look elsewhere. Aggressive red-headed finches, on the other hand, will typically respond by initiating a physical conflict for the resource.

We can examine situations of this nature using the game-theoretic concepts we have covered in class. Imagine a simple two-player situation, in which two finches are competing for edible plant seeds. The seed yields could be modeled as follows:


   A \ B              |   Aggressive               Passive    
   Aggressive      |   Medium, Medium      High, Low  
   Passive           |   Low, High                Low, Low   


A passive demeanor results in the finch obtaining only those seeds not contested by the other finch, or by other environmental factors, such as animals of other species. In general, we can expect a passive strategy to produce a relatively low yield. The highest yield should be seen by an aggressive finch competing against a passive finch. Finally, in the case of two aggressive finches, both should see relatively higher yields than in the double-passive case, but not quite as high as in either agressive-passive case.

Of course, this is a very simplistic model; for one thing, we do not account for the increased energy expenditure and risk of injury or death associated with an aggressive strategy. The point that our model suggests, however, seems pretty reasonable: that an ideal approach for the finch population as a whole to maximize resources obtained is to take a mixed strategy, in which some percentage of finches are aggressive, and others choose to be passive. This is, in fact, reflected in real-world Gouldian finch populations, in which 70% of members are passive, black-headed birds, while the other 30% are red-headed and aggressive.



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