Primates, represented by 521 species, are distributed across 91 countries primarily in the Neotropic, Afrotropic, and Indo-Malayan realms. Primates inhabit a wide range of habitats and play critical roles in sustaining healthy ecosystems that benefit human and nonhuman communities. Approximately 68% of primate species are threatened with extinction because of global pressures to convert their habitats for agricultural production and the extraction of natural resources. Here, we review the scientific literature and conduct a spatial analysis to assess the significance of Indigenous Peoples’ lands in safeguarding primate biodiversity. We found that Indigenous Peoples’ lands account for 30% of the primate range, and 71% of primate species inhabit these lands. As their range on these lands increases, primate species are less likely to be classified as threatened or have declining populations. Safeguarding Indigenous Peoples’ lands, languages, and cultures represents our greatest chance to prevent the extinction of the world’s primates.
Bearded sakis (genus Chiropotes) are among the most highly specialized primate seed predators. However, long-term studies of the genus in continuous forests, with a full community of sympatric primates, are rare. Here I present data on monthly variation in the diet of Chiropotes sagulatus from a long-term study in a continuous forest in Guyana. Bearded sakis had an extremely diverse diet, exploiting more than 175 species of plants. Consistent with their highly specialized dental morphology for seed eating, seeds made up 75% of the annual diet. Sakis exploited a wide variety of mechanically protected fruits and often exploited the same plant species for more than 3 months. They consumed a high percentage of seeds in all months and seed consumption was significantly correlated with fruit abundance. When fruit became scarcer, sakis consumed a higher percentage of non-seed food items, including insects, mature fruit, and flowers. Insects were especially important during the leanest months, making up almost 40% of feeding time. Bearded saki dietary diversity (in terms of plant species) showed little variability across months. These results confirm sakis to be highly specialized seed predators. Sakis preferentially consume seeds when they are available. However, when seeds become scarce, sakis become generalists, supplementing their diet with mature fruit, insects, and flowers. The ability of bearded sakis to consume a diversity of highly abundant plant species, fruit in several stages of maturity, and a variety of different types of resources buffers them from the detrimental effects of resource scarcity.
Pitheciids are known for their frugivorous diets, but there has been no broad-scale comparison of fruit genera used by these primates that range across five geographic regions in South America. We compiled 31 fruit lists from data collected from 18 species (three Cacajao, six Callicebus, five Chiropotes, and four Pithecia) at 26 study sites in six countries. Together, these lists contained 455 plant genera from 96 families. We predicted that 1) closely related Chiropotes and Cacajao would demonstrate the greatest similarity in fruit lists; 2) pitheciids living in closer geographic proximity would have greater similarities in fruit lists; and 3) fruit genus richness would be lower in lists from forest fragments than continuous forests. Fruit genus richness was greatest for the composite Chiropotes list, even though Pithecia had the greatest overall sampling effort. We also found that the Callicebus composite fruit list had lower similarity scores in comparison with the composite food lists of the other three genera (both within and between geographic areas). Chiropotes and Pithecia showed strongest similarities in fruit lists, followed by sister taxa Chiropotes and Cacajao. Overall, pitheciids in closer proximity had more similarities in their fruit list, and this pattern was evident in the fruit lists for both Callicebus and Chiropotes. There was no difference in the number of fruit genera used by pitheciids in habitat fragments and continuous forest. Our findings demonstrate that pitheciids use a variety of fruit genera, but phylogenetic and geographic patterns in fruit use are not consistent across all pitheciid genera. This study represents the most extensive examination of pitheciid fruit consumption to date, but future research is needed to investigate the extent to which the trends in fruit genus richness noted here are attributable to habitat differences among study sites, differences in feeding ecology, or a combination of both.
According to optimal foraging theory and most current models of primate socioecology, primate foraging involves a series of decisions concerning when is the most optimal time to leave a food patch, how to travel to the next patch in an efficient manner, and how to minimize the time and distance traveled to all patches throughout the course of the day. In this study, I assess how bearded sakis solve these challenges by presenting data on their patch use, distance minimization, and by comparing their movements with non-deterministic foraging patterns. The study group, composed of 38 ± 15 individuals, fed significantly longer in higher quality patches (quality defined by patch size and productivity) and in those that contained ripe fruit pulp. However, group size was not a significant predictor of patch occupancy. Bearded sakis traveled relatively directly between food patches, sometimes over distances > 300 m. In addition, they chose the optimal daily path among all patches visited on 9 of 17 occasions, and on average traveled only 21% more than the least distance route. Bearded saki step lengths were consistent with a Brownian rather than a Lévy Walk pattern while waiting times were consistent with a Lévy pattern. However, the distribution of their turning angles indicated a high degree of directional persistence between patches. These results suggest that bearded sakis exploit food patches that are randomly distributed spatially but heterogenous in patch quality. They appear to encode the locations of high quality food patches and minimize travel between them, despite opportunistically feeding from more abundant and randomly distributed, lower quality patches en route.
This study examines how northern bearded sakis (Chiropotes sagulatus) in Guyana adjust group cohesiveness according to the distribution and quality of food patches. I introduce a GIS based method for quantifying food patch quality and how it relates to bearded saki group spread and group size. While the concept of food patch is central to most models of primate socioecology, defining what constitutes a patch has been notoriously problematic in primate studies. In addition, researchers have struggled to quantify group spread and group cohesiveness. Advances in spatial analysis software in the last decade now allow primate researchers to better quantify these variables. Group spread in bearded sakis was not significantly greater in lower quality patches and sakis were not more spread out during feeding than during other activities. However, the study group was significantly less spread out during social behavior. Bearded saki group size was significantly correlated with both monthly fruit abundance and patch quality. In fact, mean daily patch quality explained ∼40% of the variation in foraging party size. These results suggest that bearded sakis may rely on a highly fluid social structure to mitigate the effects of intragroup feeding competition while living in large groups. Sakis do not adjust group spread on a patch-by-patch basis but rather fission into smaller foraging parties when resources become scarce seasonally and patch quality is low. This study shows that GIS is a powerful tool for modeling the relationship between group cohesiveness and resource quality and distribution.
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