Comportamento de bugios (Alouatta clamitans Cabrera, 1940) na Ilha Grande, RJ

Abstract

Alouatta clamitans is an endemic species of the Atlantic Forest, biome that has been continuously reduced, which makes extremely urgent the knowledge about the species. In the State of Rio de Janeiro, its range covers the region of Ilha Grande, municipality of Angra dos Reis. The Ilha Grande has an extensive conservation area, the State Park of Ilha Grande, which operates in the conservation of approximately 62.5% of its extension. The isolation of species on islands can cause the development of behavioral and morphological different characteristics of the species on the continent. However, there are no systematic studies on the ecology and behavior of the species on site. This study examines aspects of the behavior of Alouatta clamitans in Ilha Grande, contributing to a better understanding of the biology of the species. During nine months we recorded data on the composition and social behavior of groups through scan sampling and all-occurrences observations. It was observed that the average size of the groups was five individuals and the social composition of groups was represented by one to two adult males, one to three adult females and immature of different age, with predominantly uni-male groups. On average, the groups consisted of 22% of adult males, 38% of adult females, 4% of subadult males, 27% of juveniles and 9% of infants. The most observed behavior was the resting (45.2%), followed by feeding (28%), displacement (21.7%) and social behavior (5.1%), and among social behaviors, the most displayed was vocalization (45.8%), followed by grooming (33.7%), agonistic (7.9%), play (5.8%), rubbing behaviors (4.2%) and sexual behavior (2.6%). There were no statistically significant differences in these activities between the dry and rainy seasons. The vocalizations were predominantly emitted by males and adults, and were related to encounters of groups. The grooming behavior had the adult females as the main initiators and the adult males, the main receptors, being performed during the behavior of resting, after mating, during and after group encounters and after chasing. The agonistic behaviors were related to the group encounters in 40% of the records and in 33.3% of them occurred among females and appeared to be associated with competition for food and space, but there were no reports of physical aggression. The rubbing behavior involved the use of throat and back and was related to inter-group encounters and with the rainfall. Five copulations were recorded during the study period, in September, October and February and lasted less than a minute. In encounters with other species of primates, the howler monkeys seemed to be neutral to stimuli. The data on group composition, activity patterns and social behavior observed in Ilha Grande, in general, were similar to results obtained in other studies on the species and the genus, so that we can conclude that the groups, even residents on an island, showed no significant behavioral changes that can differentiate them from the continental populations studied.