The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)

Are primate folivores ecologically constrained? A comparative analysis of behavioral indicators of within-group feeding competition


Department of Anthropology, University of Texas at Austin

Friday 4:00-4:15, Ballroom C Add to calendar

Exhibiting an ambiguous relationship between group size and daily path length, folivorous primates are thought to experience little feeding competition. However, previous studies lacked sufficient control for ecological variation and the phylogenetic relationships among the taxa being compared. Controlling for phylogeny and key ecological variables, I examined how daily path length and relative ranging cost influence group size in 37 primate species, including 18 folivores. I also examined group size effects on group spread, activity budgets, and the ratio of infants:females since these variables have been found to index feeding competition among folivores. Relative ranging cost was not a significant predictor of folivore group size, although larger groups traveled significantly farther per day, showed increased group spread per individual, and had lower infant:female ratios than smaller groups. Larger groups also spent more time feeding and less time resting than smaller groups; however, these trends were not significant. A strong phylogenetic signal was detected among species’ mean values for average group size (PGLS, λ = 0.827). Because primate group size and behavior reflect adaptation to present-day environments and phylogenetic inertia, future analyses of feeding competition should take into account both current ecological conditions and the phylogenetic structure of the taxa being compared. Furthermore, including alternative indicators of feeding competition (e.g., increased group spread, changes in activity budgets, and decreased female fecundity) in comparative analyses may provide a better assessment of such competition in folivores, improving our current interpretations of the ‘folivore paradox’ and the competitive regime of leaf eating primates.

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