Spatial dynamics and the evolution of social monogamy in mammals

Social monogamy is an uncommon mating system among mammalian species, and several hypotheses have been suggested to explain its evolution. It is generally thought that low local population densities and widely spaced female home ranges, particularly small home ranges, may facilitate social monogamy. We tested these expectations with a complete data set on local density, home range area, and body mass for 64 mammalian species, 22 of which were described as socially monogamous and 42 as not socially monogamous (socially polygynous or polygynandrous). Larger samples were examined separately for local density (84 species) and home range size (129 species). We found that with or without statistical adjustments for body size and phylogeny, socially monogamous and nonmonogamous species appeared similar in local density and home range area. Thus, we found no support for the idea that low population densities and wide dispersion of small home ranges have favored the evolution of social monogamy. Given support for different hypotheses in studies of different species, we suggest multiple causes of social monogamy among mammalian species.