RESUMEN
Data obtained over a 7.5 year period from a captive group of sooty mangabeys were analyzed to examine the relationship between demographic variables and reproductive events. Perineal swelling and reproductive data collected from 67 females contributed to the analyses. Sexual maturation, as marked by the onset of swelling cycles, was recorded at an average age of 36.4 ± 1.1 (mean ± SEM) months and first parturition at 56.5 ± 1.8 months, indicating a period of adolescent sterility of over 1 year. A total of 198 births were recorded, of which 165 (83.3%) were live births with infant survival to 30 days of age. Both parity and the duration of infant survival influenced interbirth interval, with the shortest interval observed in multiparous females with infants surviving less than 6 months (10.0 ± 0.5 months) and the longest in primiparous females with infants surviving more than 12 months (22.4 ± 1.2 months). Infant survival did not vary significantly according to the age class of the mother. Births and the onset of perineal swellings in young females showed a seasonal distribution, with swelling cycles and conceptions rarely occurring from April through September.
RESUMEN
Sixty-five interactions where an adult male carried an infant in the proximity of a second male were observed during a 19-mo period in a captive sooty mangabey (Cercocebus atys) social group. The behavior was distributed nonrandomly in both the adult male and infant classes. In all but three of the interactions, the recently deposed alpha male carried an infant in the presence of the newly ascendant dominant male. In the first phase of the study, infants that were carried included the entire unweaned infant cohort (n = 5) born before the rank reversal. The rate of carrying in this class declined as a function of increasing infant age and time since the rank reversal. Infant carrying was not observed in the context of fighting, which was rare, and intermale aggression never preceded the behavior. However, in 40% of the cases, carrying occurred after an infant had been threatened by the dominant male. These results suggest that infant carrying served to protect the infant from aggression rather than to exploit the infant as an agonistic buffer. The data did not unequivocally support the postulate that carrying may be a form of paternal care since paternity could not be assessed. The similar structural and contextual patterns of infant carrying in this species suggest a common origin for triadic male-infant interactions in mangabeys and baboons.
RESUMEN
Aggressive behavior by an adult male toward selected infants and their mothers was observed during a long-term study of reproduction in a captive social group of sooty mangabeys (Cercocebus atys). The highest-ranking adult male in this group was observed to attack and bite three neonates out of a total of 13 infants born in 1982. All three attacks were directed attacks in which infants were grabbed from their mothers and bitten in the head. The first infant was fatally injured; the other two probably would have sustained fatal wounds had the male's canines not been blunted beforehand and had observers not intervened. The attacks were preceded by a pattern in which the male persistently stalked or chased the mother-infant pairs, a behavior first observed in the hours immediately following parturition. Unlike attacks in wild baboon groups following male immigration, these attacks on infants occurred in a stable social group in which the male attacker had been a lifelong resident. This male, however, had gained alpha rank only 3 months before attacking the first infant. These attacks, in the context of other evidence of aggression and wounding, are discussed relative to current models of infanticide in primates.
