CONICET | Buscador de Institutos y Recursos Humanos

Evolutionary models of primate social organization emphasize balancing the benefits and costs of group living, often through enjoying predator avoidance while suffering increased feeding competition. As groups increase in size they may respond by spending greater time and energy increasing their day range traveling to additional feeding sites in order to maintain sufficient nutrient intake. We used published data for approximately 100 primate species to investigate the relationship between group size and day range while controlling for the confounding effects of body size and phylogenetic non-independence among species data points. In addition, we explored average values for the ecological cost of transport (ECT), a measure derived from body mass and day range observations that indexes the percentage of daily energy expenditure devoted to travel. Multiple regression analysis identifies group size as a strong positive determinant of day range, and thus ECT, independently of body mass. This interspecific trend is strong in both the species values and phylogenetically independent contrasts. Regardless of body size, primate species living in larger social groups tend to have larger day ranges. Species residuals from the multiple regression help identify dietary correlates of day range that are corroborated by the contrast residuals implicating dietary grade shifts among primate groups. While day range and ECT are related to group size, values for ECT are quite low (median 1.45%), suggesting that the burden imposed by increased travel costs in primate groups, independently of their sizes, may be relatively minor.

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