Resposta comportamental de sagui-comum (Callithrix jacchus) à simulação de intrusos em um ambiente semiárido

Abstract

Intergroup interactions are important events in species of animals living in cooperative breeding societies, giving the opportunity for affiliative interaction, besides the agonistic ones related with resource defense. In common marmosets, Callithrix jacchus, these encounters play an important role in the social dynamics of the species. Observational studies suggest multiple functions for these encounters, such as food defense, mate defense, and reproductive opportunities outside the group. However, evaluating the contribution of these different aspects involved in intergroup interactions is a challenging task. In this sense, experimental studies simulating invaders under controlled contexts are very useful. This way, our objective was to understand the role of intergroup encounters in common marmosets, testing the hypothesis of territorial defense, mate defense, and evaluation of breeding opportunities using playbacks to simulate intruders. The study was developed with three groups living in the Caatinga, at the Baracuhy Biological Field Station (7 ° 31'42 "S, 36 ° 17'50" W), in the municipality of Cabaceiras, Paraíba, between May and December 2016. To test our hypotheses, we performed experiments with playbacks of sole males and females from the nuclear and peripheral areas of their home ranges. The strength of groups’ reaction (speed to arrive in the 5-m radius of the loudspeaker, percentage of group members that arrived at loudspeaker location, time interval in the radius of loudspeaker) was independent of the sex of the simulated intruder but was greater when the intruder was simulated in the nuclear areas. Breeding males and females moved faster towards opposite-sex intruders. When the simulated invader was of the same sex, the breeding females exhibited aggressive displays (piloerection). The same was not observed for males. Our results indicate that territorial defense is not the only motivation that drives the behavior of common marmosets in response to intruders, as these events also offer opportunities to assess extra breeding opportunities, which also result in motivation for mate defense, suggesting that such encounters may play different significant roles in the social life of these primates.