DEDUCING IMPLICATIONS OF FITNESS MAXIMIZATION WHEN A TRADE-OFF EXISTSAMONG ALTERNATIVE CURRENCIES

While the theory of natural selection posits that those behaviors maxi mizing reproductive success (''fitness'') tend to survive, behavioral ecologists more frequently explain observed behaviors as maximizing so me ''currency'' on which fitness depends. In the case of optimal forag ing theory, for example, the currency is the long-term rate of energy intake. This currency approach is adopted because little is known abou t the form of the fitness function itself. A weakness of the approach is that reproductive success often depends on more than one currency a nd behaviors which augment one currency may reduce another. We explain how to deduce from the hypothesis of fitness maximization testable qu alitative and quantitative predictions about behavior when such trade- offs exist among currencies and little is known about the fitness func tion. The methodology we describe is central to microeconomic theory, and its usefulness explains the central role accorded ''efficiency con ditions'' in that theory. We expound the approach entirely in terms of two biological examples: a preliminary example involving flower repla cement by a perennial and a more elaborate one involving over-winter h oarding by a female mammal.