Proximate factors mediating "contact" calls in adult female baboons (Papiocynocephalus ursinus) and their infants

"Contact" calls are widespread in social mammals and birds, but the proxima te factors that motivate call production and mediate their contact function remain poorly specified. Field study of chacma baboons (Papio cynocephalus ursinus) revealed that contact barks in adult females were motivated by se paration both from the group at large and from their dependent infants. A v ariety of social and ecological factors affect the probability of separatio n from either one or both. Results of simultaneous observations and a playb ack experiment indicate that the contact function of calling between mother s and infants was mediated by occasional maternal retrieval rather than coo rdinated call exchange. Mothers recognized the contact barks of their own i nfants and often were strongly motivated to locate them. However, mothers d id not produce contact barks in reply unless they themselves were at risk o f becoming separated from the group.