Influência de fatores ambientais e socioecológicos no comportamento de movimento dos bugios-ruivos (Alouatta guariba clamitans) em uma floresta contínua

Abstract

Movement is fundamental for animals, allowing them to adapt, search for resources and partners, and avoid threats. Primates, such as howler monkeys (Alouatta spp.), use cognitive maps to navigate heterogeneous environments, adjusting their space use strategies according to resource availability, the presence of competitors, and environmental factors. In this study, we investigate how socioecological and environmental factors influence the space use strategies of southern brown howler (Alouatta guariba) in a large-scale environment. In the first chapter, we assess how environmental and socioecological variables impact the daily path length (DPL) of southern brown howlers, using a path analysis approach. In the second chapter, we examine the factors influencing movement decisions and analyze how age and sex affect leadership by applying the change point test (CPT) and binomial logistic regression models. We followed a group of southern brown howlers between August 2023 and January 2024 (344 hours) in Carlos Botelho State Park, located in southern São Paulo state. Behavioral and spatial data were recorded every 5 minutes using scan sampling. For each movement, we recorded the sex and age class of the leader, as well as all feeding events, vocalizations, and encounters with conspecifics and heterospecifics. In the first chapter, we found that on days with higher leaf consumption, the southern brown howlers reduced their DPL, while fruit consumption had no significant effect. On days with higher minimum temperatures and longer daylight, the monkeys increased their resting time, thus reducing the DPL. Encounters with southern muriquis and capuchin monkeys increased the DPL, but encounters with conspecifics did not. These results suggest that, as expected for folivorous primates, rest is crucial for compensating the energetic costs associated with leaf digestion and thermoregulation, impacting the DPL. Furthermore, the presence of larger competitors, such as the southern muriquis, or more aggressive ones, like capuchin monkeys, forces the southern brown howlers to abandon feeding and resting sites to avoid direct confrontations and resource competition, which increases the DPL. In the second chapter, we observed that feeding was more frequently associated with decision-making points than other behaviors, such as vocalizations and resting. Adults had a 95% probability of leading, highlighting the crucial role of experience in collective decisions. Males led 64% of the time towards feeding sites, suggesting that factors such as body size and the need to defend the group in encounters with heterospecifics may influence this dynamic, in addition to their central role in territorial defense and vocal confrontations during conspecific encounters. These results highlight the ability of southern brown howlers to adjust their space use strategies and leadership patterns in response to various ecological and social factors. The interaction between diet, environmental conditions, and the social structure of the group directly influences space use patterns, leadership, and decision-making during group movements.