Feeding Rates and Population Growth

Numerous studies of natural populations have generated data relating foraging activities, the quantity and quality of available food resources, and population dynamics. In order to interpret these data we develop a comprehensive theorectical framework by constructing a model of foraging behavior and population growth in terms of energetic cost—gain functions. With total energy costs and gains of foraging viewed as functions of the quantity of food consumed per unit time, a simple graphical model indicates a range of profitable consumption rates. The organisms's choice of feeding rates within this range depend upon the foraging strategy adopted. A foraging strategy that mixmizes net energy gain results in a higher consumption rate than a strategy that minimizes the time spent foraging. As the population increases, energy costs of foraging may rise, and this results in a reduction of feeding rates by energy maximizers while time minimizers increase their feeding rate. As a population approaches its carrying capacity, the consumption rates of energy maximizers and time minimizers converge. An explicit dynamic model indicates the relationship between the population growth and the energetic parameters underlying its foraging activities. For example, the biotic potential, r, is found to be proportional to the maximum net gain from a numit of resource and to the equilibrium consumption rate. Comparing the population growth of "optimal foragers" with other strategies in the model the optimal foraging strategy yields a more rapid appoach to equilibrium.