CONICET | Buscador de Institutos y Recursos Humanos

There exists a growing body of evidence that increased fitness benefits accrue to individual males and individual females that reside in a functioning, stable, and affiliative social group. This results from the fact that social animals commonly encounter situations in which the collective actions of several individuals can provide benefits to each. In this study we present data based on a 21 month field investigation of within-group social tolerance and collective action in male black and gold howler (Alouatta caraya) monkeys residing in two mulitmale-multifemale social groups. Our results indicate that resident male A. caraya are highly tolerant of each other across a range of contexts including feeding, foraging, resting, and mating. Males are often each others nearest neighbor, engage in bouts of intrasexual grooming and embracing, and act jointly in excluding extragroup males and neighboring males from the vicinity of the group. On average, males invested almost 2 hours per day in intergroup encounters (Group X: 117.1 ± 94.4 minutes; Group G: 117.8 ± 94.2 minutes). Intergroup encounters were characterized by co-operative adult male boarder vigilance (56%), howling (41%), and fighting (3%). During these encounters an average of 3 resident males acted collectively to expel intruder males from the group and to interfere with mating activities between nonresident males and resident females. We conclude that concepts of reciprocity and mutualisms are central to an understanding of collective action among male black and gold howler monkeys (Alouatta caraya). Collective action enhances group cohesion and the benefits that individuals receive by maintaining coordinated, strong and predictable social bonds.

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