Squirrel monkeys (Saimiri collinsi) are seasonal breeders that live in large social groups in which females are dominant to males. Females have one infant per year, and the nursing period lasts six to eight months. Preliminary observations in the wild indicated that during the mating period (eight weeks: July and August in our population), the infants show agonism directed at males who approach their mothers. This directed sexual interference by infants has rarely been reported for neotropical primates. Our study reports observations in a natural population of Saimiri collinsi with the aim of describing the social behavior of infants during the breeding season, especially with regard to adult males in the group. Infants of both sexes were observed during three mating periods (2011, 2012, 2013), to test hypotheses about the possible function of infant harassment directed at adult males. The behavior of infants (variables: activity and nearest neighbor) was sampled by the focal animal method as well as ad libitum observations. We recorded 99 cases of agonism and 17 cases of tolerance between nearby males and infants via the all-occurrence method. Thus, 85% of interactions between adult males and infants involved agonism. These results suggest that infant interference can present a cost to adult males during the breeding season.

Llevamos a cabo un reconocimiento de corta duración de los bosques pre montano y montano de la Región Cajamarca para determinar las especies de primates que la habitan e identificar las amenazas para la supervivencia de sus poblaciones. Desde Octubre a Noviembre de 2012 se realizaron censos por transecto en nueve puntos de muestreo pertenecientes a los sectores de Huamantanga y Torohuaca y adicionalmente entrevistamos a nueve personas. En 218 km recorridos fueron registrados 20 grupos pertenecientes a Alouatta seniculus (6 grupos), Cebus yuracus (6 grupos) y Aotus sp. (8 grupos). El tamaño promedio de los grupos fue 3.2 para Aotus sp., 7.7 para A. seniculus y 14.0 para C. yuracus. La tasa de avistamiento más alta fue para Aotus sp. (6.6 a 7 individuos/10 km y la más baja para A. seniculus (1.92 a 2.54 individuos/ 10 km). En el caso de Aotus sp., no fue posible identificar la especie, pero podría tratarse de A. vociferans o una especie nueva. En el área de estudio, las principales amenazas para la supervivencia de los primates son la deforestación y quema de la vegetación.

In Brazil, the destruction of the Atlantic forest and the Caatinga dry forest continues to the present, having a profound effect on the non-human primates. Here we present data on abundance of the critically endangered Callicebus barbarabrownae (Pitheciidae), the only primate endemic to the Caatinga, and evaluate if human presence impacts their distribution. We conducted over 152 km of line transect surveys, mostly in semi-deciduous forest near the Chapada Diamantina National Park, NE Brazil. The blond titi monkey occurred at an extremely low abundance, even when considering calls their abundance was lower than that reported for closely related species in different Atlantic forest areas surveyed previously. Although hunting pressure is high in the area, the reasons for their lower abundance are yet unclear. The presence of taller and relatively undisturbed forest seemed key factors for the presence of the species even in areas with heavy human presence. We speculate that they could prefer wetter habitats and gallery forests. Our results are the first record of blond titi monkey in protected area. The long term survival of this critically endangered species may depend on increasing the number of conservation units and stimulating conservation awareness in the local human population.

Sex-segregation occurs in a number of mammals, and is typically attributed to differences in body size, reproductive energetics, or social roles. Although most primates remain in cohesive groups, spider monkeys exhibit fission-fusion dynamics and sex-segregated association patterns. Here, I present results on sex differences in behavior and subgrouping in juvenile spider monkeys. I found that the monkeys exhibit several aspects of sex-differentiated behavioral and grouping patterns that emerge despite the fact that both sexes ranged with their mothers. I conclude that juvenile spider monkeys exhibit sex-segregated behavior and association patterns earlier than previously reported for this species. Because the hypotheses regarding body size dimorphism and reproductive energetics do not apply to these juveniles, I attribute these differences to social roles.