Emigration as a Possible Mechanism Permitting the Regulation of Population Density Below Carrying Capacity

A tendency to emigrate can be shown to have selective advantages under certain conditions. These advantages appear to be best fulfilled by a density-responsive type of emigratory drive, that is, one in which a sensitivity to increasing density levels may release emigratory behavior before the carrying capacity of the population's environment is reached or exceeded. Where this is true, a genetic balance is postulated between a tendency to emigrate and a tendency to be sedentary. Such a balance could then result in "premature" density regulation by emigration under circumstances or at times in which the carrying capacity was unusually great or in situations where high intensity of emigration was particularly important. Moreover, it seems likely that if the density-responsive emigratory impulse happened to be frustrated by barriers or lack of a density gradient, density regulation may occur through the hyperdevelopment of those very factors which ordinarily bring about emigration. Some possible implications of this proposed mechanism to theories of population regulation are discussed.