How do demographic and social factors influence parent-offspring conflict? The case of wild black and gold howler monkeys (Alouatta caraya).

In this study, we examined the influence of demography and social context on mother-offspring conflict in wild black and gold howler monkeys (Alouatta caraya) inhabiting two nearby sites in northern Argentina, one comprising continuous forest and one fragmented forest. These sites differed in population density (3.25 vs. 1.04 individuals/ha), degree of home range overlap between neighboring groups (70 vs. 31%), and rate of intergroup encounters (2 vs. 0.02-1 encounters/day), though not in interbirth interval or rate of infant mortality. During a 27-month study (September 2008 through November 2010), we observed 37 mother-offspring dyads across the two sites. We found a very similar pattern of mother-offspring conflict in both populations; specifically, the sites did not differ in any of the variables used to characterize the mother-offspring relationship (the time spent in contact, the rate at which the mother makes and breaks contact, the rate at which the infant breaks contact, the rate of maternal rejection, and signs of infant distress) except one (the rate at which the infant makes contact). Although mother-offspring conflict is a dynamic process that varies over time, our results suggest that the different demographic and social contexts found at the two study sites did not have a marked effect on quantitative aspects of the mother-offspring relationship in these populations of black and gold howlers. Finally, this study suggests that the environmental variability (ecological, demographic, and social traits) leads to a set of strategies used both by infants and mothers with a main goal of conflict resolution, with mothers specifically aiming to cope with the tradeoff between current and future reproduction.