Ecologia e comportamento do bugio-ruivo (Alouatta guariba clamitans) em um fragmento florestal no limite sul da distribuição : testando predições de modelos socioecológicos

Abstract

This study investigated the activity budget, diet composition and the frequency of intergroup encounters and howling sessions of three social groups of brown howler monkeys (Alouatta guariba clamitans) to evaluate the occurrence of within- and between-group feeding competition and test predictions of socioecological models applied to folivorous primates. The groups inhabited a 10-ha forest fragment near the southern limit of the distribution of the taxon. The availability of preferred food resources (ripe fruit and young leaves) of 15 arboreal species belonging to the diet of brown howlers was monitored monthly prior to the collection of behavioral data. The behavior was recorded by the instantaneous scan (activity budget and diet composition) and the all occurrences (intergroup encounters, agonistic behaviors and howling sessions) sampling methods during 4 to 5 days per month (February to July 2012) per group. A total of 17,184 behavioral records were collected in 910 hours of observation. Resting was the most common activity (50-54%), followed by feeding (21-23%) and moving (17-21%). The diet was composed mainly of leaves (48-54%) and fruit (39- 45%). There were 52 intergroup encounters, 3 intragroup and 13 intergroup agonistic interactions and 245 howling sessions. Therefore, in accordance to previous studies, the brown howler monkeys were involved in low levels of both within- and between-group resource competition. However, the availability of new leaves and ripe fruit were good predictors of the rate of intergroup encounters and howling sessions by some groups, allowing to suggest that howler monkeys appear to reduce the frequency of encounters with conspecifics by using howling as a behavioral mechanism for maintaining intergroup spacing and obtaining access to sources of preferred foods.