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

Abstract

Primates within the Alouatta genus (howler monkeys) inhabit a wide range of environments due to their flexible folivorous-frugivorous diet. However, the feeding ecology of Alouatta species that inhabit continuous and difficult-to-access forest environments, such as the Amazon, is poorly known. In this study, we compared diet composition, seed size, and richness of fruits ingested by Juruá red howler monkeys (Alouatta juara) in white-water flooded forest and upland for- est. Our analysis was based on 47 stomachs donated by subsistence hunters of central Amazonia in Brazil. We found no difference 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 flooded forest. This correlation was not observed for upland forest, where other environmental factors such as precipitation may influence tree phenology. The stomach analysis revealed a high diversity of seeds and a substantial percentage of whole seeds (73%) in the red-howler monkeys’ stomachs. This suggests that they have the potential to be effective seed dispersers for at least 40 taxa in the white-water flooded forest and 14 in the upland forest. The 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. These 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.