| Abstrakt: |
Previous research has suggested that the quiet, tonal grunts given by female savanna baboons (Papio cynocephalus ursinus) function to mollify lower-ranking females and thereby facilitate friendly social interaction with them (Cheney et al., 1995). In a two-year study of wild chacma baboons, we assessed whether or not grunts given by adult males function similarly to facilitate heterosexual interaction. Two patterns of male vocal behavior initially suggested this function. First, males grunted more often when approaching females with which social interaction was potentially highly beneficial and/or unlikely (due to female evasion), i.e. estrus females and lactating females (particularly friend females); males rarely grunted when approaching pregnant females. Second, higher-ranking males grunted significantly more often than subordinates when approaching females in most reproductive states. In spite of these two patterns, however, male grunts had contrasting effects on the probability of supplanting a female and interacting affinitively with her. Supplanting of females was just as common when the approaching male grunted as when he did not. Instead, variance in supplanting was better explained by female avoidance of high-ranking and non-friend males than by the male's vocal behavior. Results suggest that male grunts themselves do not generally determine whether a supplant of the female occurs. Rather, the female's reproductive state and social relationship with the male (i.e. his 'friendship' status and/or rank) affect both the male's tendency to call to her and the female's tendency to move away from him. In contrast to supplanting, affinitive interaction occurred significantly more often when males grunted than when they silently approached females. Taken together, results suggest that a female chacma baboon's 'spatial' response to a male's approach ('stay or leave') depends upon her assessment of non-vocal factors, but her 'social' response ('interact or not') is influenced by the grunts given by the male. [ABSTRACT FROM AUTHOR] |
