Hawk-dove evolutionary game theory and Australian Gouldian finches
Evolutionary game theory, specifically the hawk-dove theory, is popular in the field of theoretical biology, and has been discussed on this blog several times before, but has never been actually observed in the wild–until now.
The main difficulty comes from identifying which animals are actually the “hawks” and the “doves,” which isn’t too clear-cut in the wild. (I will defer to the linked blog entries to describe exactly what the hawk-dove theory is.)
However, Australian evolutionary biologist Simon Griffith and his team have identified an instance of the hawk-dove theory, in Australian Gouldian finches. There are two varieties of this species: the rarer, red-headed finch, and the common, black-headed finch. The red-headed finches are aggressive (“hawks”) while the black-headed finches are passive (“doves”).
Griffith and his team, using the hawk-dove theory, predicted that the optimal ratio of red-to-black-headed doves is 30:70. In the field, they observed exactly this ratio.
The reason for this lies in the resources each type of finch gives to fighting and child-rearing. Aggressive, red-headed finches spend more time aggressively securing a better nest, but as a consequence have less resources to actually produce chicks. Passive, black-headed finches don’t put up as much of a fight, and thus spend more time producing chicks. Too many red-headed finches causes a decline in the population.
The ratio Griffith predicted and observed is the population’s Nash equilibrium. This is an interesting example of a real application/observance of game theory in nature.