On the adjustment of the sex ratio and the gregarious behaviour of animal populations

Abstract

Certain assumptions on the movement and signalling of a species, as well as on the dimensionality of the space, give rise to a variety of “spatial models”, and yield some conclusions relative to the gregarious behaviour of that species and the adjustment of the sex ratio in bisexual populations. In the former context, Hamilton's (1971) arguments are affected. In the latter, Kalmus & Smith's (1960) treatment is discussed and elaborated to include pertinent new factors. This is done in a quantitative manner by applying a number of occupancy models. It appears that the sex ratio which maximizes the expected number of fertilized females will be biased towards the mobile sex, subject to the relative fecundity of the males. It is argued that the optimal sex ratio constitutes a socially advantageous but individually disadvantageous character, and may survive under certain conditions.