The findings suggest that for species in which females lived alone in large territories to avoid competition for food and other resources, males were unable to defend multiple females, and therefore became monogamous.
"In mammals, social monogamy is the result of resource distribution," study researcher Dieter Lukas, of the University of Cambridge, said in a press briefing today. Females were limited by the distribution of food, and males were limited by the distribution of females, Lukas said.
Social monogamy was also more common among primates and carnivores than other species, the study found. The more specialized diets of these animals may have increased competition for food, leading females to isolate themselves.
The findings failed to support the idea that the risk of infanticide led to monogamy in mammals, even in primates. The researchers suggest the discrepancy between the two studies could be explained by differences in how group-living is classified. For instance, some species that Opie's team classified as group-living were classified by Lukas as socially monogamous. Alternatively, the smaller sample of animals in Opie's study could have skewed their findings, Lukas and his colleagues said.