Comparing diet, seed size and richness in fruit ingested by red howler monkeys (Alouatta juara) in two habitat types in Central Amazonia

Primates in the genus Alouatta (howler monkeys) inhabit a wide range of environments due to their !exible folivorous-frugivorous diet. However, the feeding ecology of Alouatta species that inhabit continuous and di"cult-to-access forest environments, such as the Amazon, is poorly known. In this study, we compared diet composition, seed size, and rich-ness of fruits ingested by Juruá red howler monkeys (Alouatta juara) in white-water !ooded forest and upland forest. Our analysis was based on 47 stomachs donated by subsistence hunters of central Amazonia in Brazil. We found no di#erence in the proportion of structural parts, reproductive parts, and animal matter (arthropods) ingested between these environments. However, we found a positive relationship between the richness of ingested seeds and the water level for the white-water !ooded forest. $is correlation was not observed for upland forest, where other environmental factors such as precipitation may in!uence tree phenology. $e stomach analysis revealed a high diversity of seeds and a substantial percentage of whole seeds (73%) in the red-howler monkeys’ stomachs. $is suggests that they have the potential to be e#ective seed dispersers for at least 40 taxa in the white-water !ooded forest and 14 in the upland forest. $e population decline or extinction of this species could have an impact on seed dispersal services, particularly for plant species with seeds larger than 20 mm of diameter, as the number of dispersing agents tends to be limited. Further studies are needed to investigate the environmental dynamics involved in the feeding ecology of red howler monkeys. $ese studies would help to understand the ecological impacts of local subsistence hunting and wild meat trading on seed dispersal, as well as the economic implications for human populations.