Ecological, social, and reproductive factors shape producer--scrounger dynamics in baboons

Producer--scrounger models are used to explain the tactics of socially foraging animals where individuals can either search for their food (produce) or join the food discoveries of others (scrounge). However, the empirical testing of such models has generally been restricted to indoor aviary experiments. Here, we examine the social foraging tactics of naturally foraging wild chacma baboons (Papio ursinus). Thirty-six adult baboons from 2 groups were observed during full-day follows: Data from nearly 10 000 foraging events were analyzed using cross-classified, generalized linear mixed models. First, as predicted by producer--scrounger models, we show that baboons altered their foraging tactics in accordance with food patch size and spatial position in the group. Second, we show that the relative characteristics of cofeeding individuals were crucial: In particular, among females, individuals were more likely to scrounge from foraging neighbors who were subordinate and with whom they had a strong social affiliation. However, we found no effect of kinship. Finally, we found that female reproductive state influenced female foraging tactics (females scrounged more from male neighbors when pregnant and less when fertile), but the reproductive state of female neighbors had no such effects on male foraging tactics. These results suggest that, in addition to broad-scale ecological and group-level influences, a myriad of social and reproductive factors can shape producer--scrounger dynamics for wild animals living in complex social groups. Copyright 2009, Oxford University Press.