Primates use different types of vocalizations in a variety of contexts. Some of the most studied types have been the long distance or loud calls. These vocalizations have been associated with mate defense, mate attraction, and resource defense, and it is plausible that sexual selection has played an important role in their evolution. Focusing on identified individuals of known sex and age, we evaluated the sexual dimorphism in a type of loud calls (hoots) in a population of wild owl monkeys (Aotus azarae) in Argentina. We found evidence of sexual dimorphism in call structure, with females and males only emitting one type of call, each differing in dominant frequency and Shannon entropy. In addition, both age-related and sex-specific differences in call usage were also apparent in response to the removal of one group member. Future acoustic data will allow us to assess if there are individual characteristics and if the structure of hoot calls presents differences in relation to the social condition of owl monkeys or specific sex responses to variants of hoot calls’ traits. This will provide deeper insights into the evolution of vocal mechanisms regulating pair bonding and mate choice strategies in this and other primate species.

There are five different primate species inhabiting widely distinct ecoregions in Argentina. Each of them faces various threats in terms of conservation and conflicts that hamper their ability to coexist with human populations. We present here some of the drivers known to be the causes of conflicts between humans and primates in the southernmost area of distribution of Latin American primates. We focus our synthesis on two of the biggest sources of conflict: the effects of different anthropogenic disturbances, and human misconceptions concerning the role of primates in the ecosystem. In each section, we briefly characterize the conflicts worldwide and then provide specific cases and examples from Argentina. In the last part of the manuscript, we further describe some ongoing national and regional educational, research, and conservation approaches to mitigate those effects.

Natal dispersal is an important life-history stage influencing individual fitness, social dynamics of groups and population structure. Understanding factors influencing dispersal is essential for evaluating explanations for the evolution and maintenance of social organization, including parental care and mating systems. The social and mating systems of Azara’s owl monkeys ( Aotus azarae ) are infrequent among mammals; these primates are pair-living, serially and genetically monogamous and both sexes directly care for offspring. To evaluate the role that competition and inbreeding avoidance play in shaping dispersal patterns, we used 25 years of demographic and genetic data to examine how variation in timing of natal dispersal is related to social (adult replacements, step-parents, births and group size) and ecological factors (seasonal abundance of resources) in a wild population of A. azarae in Formosa, Argentina. We found that all males and females dispersed from their natal groups, but subadults delayed dispersal when a step-parent of the opposite sex joined the group, indicating that they may perceive these step-parents as potential mates. Dispersal was more probable when resource conditions were better, regardless of age. Overall, agonistic conflict over food and potential mates with adults in the natal group, as well as inbreeding avoidance, contribute to regulating dispersal.

Our understanding of the viability of primates in anthropogenically fragmented habitats is undermined by the long timeframes for the effects of fragmentation to manifest. Studying primates in natural forest islands can better reveal the limits to habitat viability in the face of fragmentation. We present a study of a group of Azara’s owl monkeys ( Aotus azarae ) occupying a 0.53 ha forest “island”, the smallest such forest island and territory ever documented for the genus Aotus . We radio collared one individual and then, for ten months, collected ecological and behavioural data on the island and the group (123 scans, 44 observation days). We also collected forest structure data on the island. While the group did successfully establish itself on the island, the pair did not have an offspring during the birth season. The pair predominantly engaged in resting behaviour in close proximity to each other. Furthermore, the adult male of the group was characterised by eye deformities and bodily injuries, and eventually died nine months after we identified him. These results suggest that, while the forest island may be habitable in the short term, it may not have been sufficient for the long-term survival and reproduction. We propose that this forest island could act as a population sink, where individuals that are not competitive in the highly saturated gallery forest can reside temporarily. Our study shows the importance of considering not only presence/absence, but also behaviour and life history to consider the effects of forest island viability, especially in the face of future scenarios of anthropogenic fragmentation.