From female choice to social structure: Modeling harem formation in camelids

Herbivorous wild species constantly strive to optimize the trade-off between energy and nutrient intake and predation risk during foraging. This has led to the selection of several evolutionary traits – such as diet, habitat selection, and behavior – which are simultaneously shaped by the spatio-temporal variability of the habitat. Among camelid species, polygyny is a prevalent behavioral strategy that encompasses both mating and foraging activities. This group-level behavior has multiple interacting dimensions, contributing to an interesting ecological and evolutionary complexity. We developed an individual-based stochastic model in which camelid females transition between different familial groups in response to their environmental conditions, aiming to maximize individual fitness. Our results indicate that the behavioral strategy of individual females can shape, by itself, emergent population-level properties, including group size and fitness distribution. Furthermore, these properties are modulated, in a non-additive manner, by other factors such as population density, sex ratio and system heterogeneity. • Female choice defines stable distributions of the number of females per harem. • Bachelor males significantly modulate the population’s social structure. • Equity among harems depends on resource levels, heterogeneity, and sex ratio. • A larger group size only becomes beneficial under specific environmental conditions. • Female distribution depends on group size and quality, varying across scenarios.