Vegetative predictors of primate abundance: utility and limitations of a fine-scale analysis

Determining ecological predictors of primate abundance is important for both theoretical and applied conservation management. For forest primates, research has focused on comparisons of primate abundance and vegetation in different forest blocks or forest compartments with different management histories. However, great variation in primate abundance often occurs within single forests, especially in mountainous areas or in areas with habitat mosaics due to past disturbance. Here we assess, for the first time, the usefulness and limitations of small-scale, within-transect analysis of vegetative parameters as predictors of primate abundance in a very heterogeneous forest habitat in the Udzungwa Mountains of Tanzania. Relative abundance of four species of diurnal primates was recorded over a period of 2.5 years by walking three census transects 48 times each. Tree size, density, species composition, and food plants were measured along the same census lines. The fine-scale relationship between primate abundance and vegetative variables was analyzed through generalized linear modeling applied to 58 segments of these three census lines. Each segment was 200 m in length. For all four primate species, we found significant associations between their abundance and selected vegetative variables. The abundance of the endemic and endangered Udzungwa red colobus Procolobus gordonorum was positively related to mean basal area of large trees (diameter at breast height greater than 20 cm) and to the species richness of their food plants. Considering the very great variation in primate abundance that was recorded among segments of the census lines, our approach proved useful in predicting the relationship between primate abundance and small-scale habitat differences. The main limitation of this study, however, was the relatively low-predictive power of the models for some species, especially the Angolan colobus Colobus angolensis. We discuss the potential reasons for this problem and suggest possible improvements for future studies.     

Distribution and Abundance of Primates in Rain Forests of the Western Ghats,Karnataka, India and the Conservation of Macaca silenus

We assessed the distribution and abundance of 4 species of diurnal primates viz. lion-tailed macaque, bonnet macaque, Nilgiri langur and Hanuman langur, in 2 areas—Brahmagiri-Makut and Sirsi-Honnavara—in rain forests of the Western Ghats in the state of Karnataka, India. The Nilgiri langurs in Brahmagiri-Makut and the lion-tailed macaques in Sirsi-Honnavara are the northernmost populations of the 2 species in the Western Ghats. The 2 regions represent changes in ecological zones in the Western Ghats. In Brahmagiri-Makut, Hanuman langurs and bonnet macaques occupy lower elevations whereas Nilgiri langurs live in relatively higher altitudes. Only one group of lion-tailed macaques was in Brahmagiri-Makut. In the forests of Sirsi-Honnavara, 3 species of primates viz. lion-tailed macaque, bonnet macaque and Hanuman langur were in larger numbers throughout the forest. A self-sustainable single population of 32 groups of lion-tailed macaques occurred in Sirsi-Honnavara. Few subspecies of Hanuman langurs exist in the study regions. Due to local hunting practices, the relative abundance of primates in Brahmagiri-Makut is lower than that in Sirsi-Honnavara.     

Links between habitat degradation,and social group size,ranging, fecundity,and parasite prevalence in the Tana River mangabey (Cercocebus galeritus)

We investigated the effects of anthropogenic habitat degradation on group size, ranging, fecundity, and parasite dynamics in four groups of the Tana River mangabey (Cercocebus galeritus). Two groups occupied a forest disturbed by human activities, while the other two occupied a forest with no human disturbance. We predicted that the groups in the disturbed forest would be smaller, travel longer distances daily, and have larger home ranges due to low food tree abundance. Consequently, these groups would have lower fecundity and higher parasite prevalence and richness (number of parasite species). We measured the abundance of food trees and anthropogenic activity in the forests, the groups' daily travel distances and home range sizes, and censused social groups over 12 months. We also analyzed fecal samples for gastrointestinal parasites from three of the groups. The disturbed forest had a lower abundance of food trees, and groups in this forest traveled longer distances, had larger home range sizes, were smaller, and had lower fecundity. The groups in the disturbed forest had higher, although not statistically significant, parasite prevalence and richness. This study contributes to a better understanding of how anthropogenic habitat change influences fecundity and parasite infections in primates. Our results also emphasize the strong influence of habitat quality in determining daily travel distance and home range size in primates. Am J Phys Anthropol, 2009. © 2009 Wiley‐Liss, Inc.     

Ecological correlates of abundance in the Tana mangabey (Cercocebus galeritus)

I investigated the ecological correlates of abundance in the Tana mangabey (Cercocebus galeritus), one of the world's most endangered primates, with the goal of recommending management strategies. I systematically selected 31 forest fragments throughout the mangabey's 60-km distribution along the lower Tana River in southeastern Kenya. Within the 31 fragments, I measured vegetation structure, food abundance, and human forest product use in 107 belt transects, and conducted 370 mangabey surveys. I used a weighted multiple regression analysis to determine whether there was a dependence between the selected forest attributes and the mean number of mangabey groups per fragment. Fragment area and density of trees > or =10 cm diameter at breast height (DBH) were the only variables that significantly correlated with the variation in mangabey abundance. No additional variables were significant when the analysis was limited to forest fragments inside the Tana River Primate National Reserve (TRPNR) or to fragments outside the TRPNR. When I estimated the resources available before recent human forest product use by adding nonharvested and harvested variables, the total basal area of the top 15 food species became significant. This was only within the TRPNR, however. Management, therefore, should focus on increasing forest area, density of trees > or =10 cm DBH, and coverage of food trees throughout the mangabey's distribution. Solutions must be found for the problem of forest clearing, and forest product use must be better managed to protect the habitat of this critically endangered primate. The significance of food abundance only within the TRPNR suggests a need to collect dietary data from mangabey groups in fragments toward the southern limit of the mangabey's distribution, where plant species composition differs from that in fragments in which dietary data have been previously collected.     

High density of white-faced capuchins (Cebus capucinus) and habitat quality in the Taboga Forest of Costa Rica

Across the globe, primates are threatened by human activities. This is especially true for species found in tropical dry forests, which remain largely unprotected. Our ability to predict primate abundance in the face of human activity depends on different species' sensitivities as well as on the characteristics of the forest itself. We studied plant and primate distribution and abundance in the Taboga Forest, a 516-ha tropical dry forest surrounded by agricultural fields in northwestern Costa Rica. We found that the density of white-faced capuchins (Cebus capucinus) at Taboga is 2–6 times higher than reported for other long-term white-faced capuchin sites. Using plant transects, we also found relatively high species richness, diversity, and equitability compared with other tropical dry forests. Edge transects (i.e., within 100 m from the forest boundary) differed from interior transects in two ways: (a) tree species associated with dry forest succession were well-established in the edge and (b) canopy cover in the edge was maintained year-round, while the interior forest was deciduous. Sighting rates for capuchins were higher near water sources but did not vary between the edge and interior forest. For comparison, we also found the same to be true for the only other primate in the Taboga Forest, mantled howler monkeys (Alouatta palliata). Year-round access to water might explain why some primate species can flourish even alongside anthropogenic disturbance. Forest fragments like Taboga may support high densities of some species because they provide a mosaic of habitats and key resources that buffer adverse ecological conditions.     

Giardia sp. and Cryptosporidium sp. infections in primates in fragmented and undisturbed forest in western Uganda

In June 2005, we collected 115 fecal samples from wild primates in western Uganda and examined them for Cryptosporidium sp. and Giardia sp. with the use of immunofluorescent antibody (IFA) detection. We sampled primates from an undisturbed forest in Kibale National Park and from 3 highly disturbed forest fragments outside the park. Of disturbed forest samples, red colobus (Pilocolobus tephrosceles) and red-tailed guenons (Cercopithecus ascanius) harbored species of Cryptosporidium or Giardia, but black-and-white colobus (Colobus guereza) did not. All primate samples from undisturbed forest were negative for both parasites. Seven of 35 (20%) red colobus and 1 of 20 red-tailed guenons (5%) from forest fragments were infected with either Cryptosporidium sp. or Giardia sp. The presence of Cryptosporidium and Giardia species in primates living in forest fragments, but not in primates in undisturbed forest, suggests that habitat disturbance may play a role in transmission or persistence of these pathogens.     

Can we rely on forest reserves for primate conservation?

Tropical forests contain much of the world's biodiversity, yet their rate of decline is increasing. The strategy most frequently used to protect this biodiversity is to make parks and reserves. While there is a great deal of research on the effectiveness of parks for protecting biodiversity, there is little research on how well extractive reserves conserve biodiversity. Here, we evaluate the effectiveness of four forest reserves in western Uganda at maintaining populations of primates and compare census data from the reserves to data from the neighbouring well‐protected Kibale National Park. The relative abundance of the five most common primates in the park was approximately four times that of the forest reserves. In the forest reserves, evidence of new human encroachment was seen every 500 m, while in the park it was seen every 100,000 m. Two recommendations emerge from our research: (i) for forest reserves, such as those studied here, to have conservation value for primates, extraction must be reduced and (ii) until the long‐term viability of the populations in forest reserves can be ascertained, they should not be considered in estimates of the sizes of endangered species protected ranges.     

Habitat use of Bornean Orangutans (<Emphasis Type="Italic">Pongo pygmaeus morio</Emphasis>) in an Industrial Forestry Plantation in East Kalimantan,Indonesia

Many primates now live in anthropogenic landscapes dominated by human activity such as agriculture. Conserving primates in such contexts requires detailed information about habitat use, including landscape features that may influence population viability. We studied Northeast Bornean orangutan (Pongo pygmaeus morio) habitat use in a forestry plantation in East Kalimantan, Indonesia. We conducted camera trapping and nest surveys at 13 locations across three habitat types in the plantation (planted acacia stands, planted eucalyptus stands, and secondary forest patches left uncut or allowed to regenerate) September 2012–March 2013, and calculated four measures of orangutan abundance for each location (independent photo captures/100 camera trap days, or RAI₂; nest encounter rate; nest density; and orangutan density). Orangutans are relatively common in the plantation; they used all three habitat types and exhibited a higher RAI₂ than 70% of other mammal species detected. A logistic regression found that proximity to natural forest areas best predicted orangutan abundance calculated using camera trap data (RAI₂) but that habitat type combined with distance to natural forest best predicted orangutan abundance calculated using nest counts. This suggests that orangutans use planted areas for movement and feeding, but rely on patches of natural forest for resting and access to key resources. Our study and others indicate that orangutans can coexist with some human activities if provided with sufficient access to natural forest. However, we must conduct further research to facilitate effective conservation planning, including gathering additional details about habitat and resource use and possible long-term population impacts.     

Primate frugivory in Kibale National Park, Uganda, and its implications for human use of forest resources

In an attempt to understand the practical and/or economic implications of primate seed dispersal, it was established which seed species are dispersed by frugivorous primates in Kibale National Park, Uganda, and which of this sort of species were used by Ugandan people. A list of fruit species consumed by Kibale primates was compiled using primary data and by reviewing all known published accounts of their fruit diet. Primates consume the fruit of 87 Kibale forest tree species; the seeds of 11% of these species are destroyed by the primates. The remaining 77 species are dispersed by either one, two, three or all four of the frugivorous Kibale primates. Of these 77 species, 42% have some utility to local Ugandan inhabitants, suggesting that maintaining populations of primates is important not only for natural forest regeneration, but also for human habitat use. This report illustrates the complexity of the seed dispersal process and suggests links not only between plants and their dispersers, but also between sets of plants/dispersers and the human populations that rely on forest resources.     

Edge Effects on Species Composition and Exotic Species Abundance in the North Carolina Piedmont

Edges between forest and non-forest habitats often have significant effects on forest microclimate and resource availability, with corresponding effects on species composition and abundance. Exotic species are often increased in abundance near forest edges. This increase in abundance could be either because of the increase in resource availability near edges, or because of increased dispersal into forest edges. We measured species composition and a set of geospatial variables on transects at 66 edges in the North Carolina Piedmont in an attempt to distinguish between these two factors. Mantel tests show that species composition is significantly different in forest edges than in the forest interior, but that this effect only penetrates about 5 m into the forest. Indicator species analysis finds several species that are indicative of edge communities, including trumpet vine (Campsis radicans), two drought-tolerant oak species (Quercus stellata and Q. falcata), a serviceberry (Amelanchier arboreum), and a common exotic species, tree-of-heaven (Ailanthus altissima). Poisson regression techniques showed that in both the seedling and tree strata of the forest, exotic species increased in abundance on flat sites with a high potential seed source. Mapping predicted exotic species abundance onto the landscape. We find that large-scale variation in exotic species abundance is due mostly to variation in potential seed sources, while small-scale variation relates more to edaphic factors. Our results stress that both dispersal and environmental filters are important for determining exotic species abundance, but potentially the filters operate at different spatial scales.     

Long-term dynamics of wild primate populations across forests with contrasting protection in Tanzania

Anthropogenic activities driving tropical forests' loss imperil global biodiversity and provision of ecosystem services. In this context, systematic monitoring programs evaluating wildlife trends are essential. Non-human primates are relevant conservation targets since they represent vital components of tropical forests by serving as pollinators and seed dispersers. Here, we present primate group counts data collected over 19 years in a primate hotspot in Tanzania. We analyzed data with a hierarchical dynamic model accounting for imperfect detection that estimates local group abundance and temporal rates of change, to assess whether habitat protection explained trends of the arboreal and diurnal Peters' Angola colobus (Colobus angolensis palliatus), Udzungwa red colobus (Piliocolobus gordonorum), and Tanzania Sykes' monkey (Cercopithecus mitis subsp. moloneyi). We targeted populations occurring in two forest blocks with contrasting protection regimes, with one block impacted by targeted poaching of the two Colobus species. We found that these latter species were much less abundant in the more human impacted forest, underwent a rapid decline, and subsequently remained at low abundance and without signs of recovery once this forest was granted greater protection. Instead, Sykes' abundance did not differ between forests, and improved protection was associated with a slight increase in abundance. Age class composition for social groups of both Colobus species differed between forests, indicating altered births and survivorship rates in the impacted forest. Results suggest that targeted hunting can prevent recovery for several years and even after increased habitat protection. Our approach appears valuable to monitor population dynamics over the long term, highlighting species-specific variations in both vulnerability to anthropogenic disturbance and recovery patterns in primate populations.     

Primate population densities in three nutrient-poor amazonian terra firme forests of south-eastern Colombia

We censused primate populations at three non-hunted 'terra firme' forests of south-eastern Colombian Amazonia. The aggregate biomass densities of diurnal primates at all sites were amongst the lowest recorded for any non-hunted forest in western Amazonia and elsewhere in the Neotropics. Densities of red howler monkeys were low, as is typical in Amazonian terra firme forests far removed from white-water rivers, and densities of woolly monkeys were 1.5-3.5 times lower than those estimated for this species in central-western Brazilian Amazonia. Densities of small to mid-sized primates except for brown capuchins (Cebus apella) and white-faced capuchins (Cebus albifrons) were similar to those of other oligotrophic Amazonian forest sites. Our results are in agreement with other studies showing that terra firme forests of lowland Amazonia typically sustain a low biomass density of primates and other mid-sized to large vertebrates. Large reserves are therefore required to assure the viability of primate populations in oligotrophic systems. Given the escalating negative impacts of human habitat disturbance and hunting in Colombian Amazonia, we urge that a baseline sampling protocol to quantify the abundance and distribution of the harvest-sensitive vertebrate fauna be established within protected areas and the large indigenous reserves so that conservation efforts can be defined and implemented.     

How do differences in species and part consumption affect diet nutrient concentrations? A test with red colobus monkeys in Kibale National Park,Uganda

Within a primate species, diet can be highly variable in composition, even at small spatial scales within the same forest, or temporally, suggesting that primates use different plant species and parts to meet similar nutritional needs. To test whether such differences in the plant species and parts that primates eat affects the nutrient concentrations that they obtain, we observed feeding of seven groups of red colobus monkeys ( Procolobus rufomitratus) residing in Kibale National Park, Uganda. The different groups consumed mostly young leaves from many of the same plant species, but spent different amounts of time feeding on them. As protein and fibre are suggested to be important determinants of colobine food choice and abundance, we analysed multiple samples of 47 food species for protein and fibre. Despite the differences in the plant species and parts eaten, the protein and fibre concentrations for the seven red colobus groups were similar. Our results suggest that colobus monkeys eating diets with differing amounts of species and parts may ultimately receive similar concentrations of nutrients.     

Structure of Brazilian Atlantic forests with occurrence of the woolly spider monkey (<Emphasis Type="Italic">Brachyteles hypoxanthus</Emphasis>)

This work examines patches of Atlantic forests in Minas Gerais State where woolly spider monkeys (Brachyteles hypoxanthus) are inhabitants in order to understand the effects of forest structure, diversity, and succession in B. hypoxanthus abundance. This study was carried out in three reserves: Rio Doce State Park (PERD), Mata do Sossego (Sossego), and Serra do Brigadeiro State Park (PESB). Structural studies were carried out by means of point-centered quarter samples in areas used by woolly spider monkeys. Evenness was lower in PERD than in the other two communities. By means of successional functional groups analysis and diametric structure, the PERD forest sample was shown to be in the later, and PESB forest sample in the earlier, stages of secondary succession. We found that tree species evenness and structural traits driven by succession were important factors in determining spider monkey abundance patterns. The PERD forest sample had lower evenness and had lower density of woolly spider monkeys than the Sossego forest sample. The lowest density of these primates was in the PESB forest sample, the earlier successional stage of secondary succession of this study.     

Primate Group Size and Abundance in the Caatinga Dry Forest, Northeastern Brazil

The Caatinga dry forest poses a series of ecological challenges for mammals in general and primates in particular. The erratic rainfall pattern impacts on plant diversity and phenological patterns; from year to year there is marked variability in fruit production and failure to fruit is common. The harshness apparently accounts for the impoverished mammalian fauna. However, data on primate abundance, distribution, and possible environmental effects on primate density are lacking in this type of dry forest. I censused the primate community in 3 habitats of the Serra da Capivara National Park, Piaui, NE Brazil, over a total distance of 318 km. Overall, the abundance of primates in the Caatinga dry forest is very low as a consequence of low abundance of food resources both in space and time. Alouatta caraya (predominantly folivorous) occurs at extremely low density, and during the dry season are apparently confined to canyon areas, where trees retain their leaves. Callithrix jacchus has morphological feeding specializations for gum-eating, and gum is an important resource during food bottleneck periods. Nonetheless, Callithrix jacchus occurs at comparatively low densities. Group sizes for howlers and marmosets in the Caatinga are significantly smaller than in other forest types. Contrarily, Cebus apella libidinosus had an average group size within the range reported for Amazonian and Atlantic forests. Researchers consider the generalized diet of capuchins as the explanation for their similar abundance in different habitats, indicating relative independence from ecological constraints. However, I suggest that capuchin foraging style and cognitive abilities are important factors accounting for their unreduced group size and density even under extreme conditions.     

紫胶林-农田复合生态系统地表甲虫多样性——以云南绿春为例

为揭示紫胶林-农田复合生态系统地表甲虫多样性, 于2006-2007年在云南省绿春县牛孔乡采用陷阱法调查了天然紫胶林、人工紫胶林和旱地的地表甲虫群落。共采集标本1 678头, 分别隶属于24科120种, 其中步甲科(Carabidae)和金龟科(Scarabaeidae)种类最丰富, 均占全部种类的12.50%。拟步甲科(Tenebrionidae)个体数量最丰富, 占个体总数的64.48%; 金龟科次之, 占个体总数的17.58%。大多数科的物种数和个体数在不同土地利用生境中的分布没有显著差异, 而步甲科、隐翅甲科(Staphylinidae)、叩甲科(Elateridae)、拟步甲科、瓢虫科(Coccinellidae)和小蠧科(Scolytidae)在不同土地利用生境中的分布有显著差异。天然紫胶林地表甲虫个体数量最少, 物种较丰富, 优势度最低, 多样性最高; 人工紫胶林个体数和物种数均丰富, 优势度和多样性居中; 旱地个体数量最多, 物种最贫乏, 优势度最高, 多样性最低。种级水平的聚类分析体现出人工紫胶林与旱地之间在种类组成上距离较近; 而科级水平的聚类反映出人工紫胶林和天然紫胶林更接近。结果提示, 紫胶林-农田复合生态系统具有区域内土地利用方式多样化的特点; 天然紫胶林在维持地表甲虫多样性水平上具有重要作用, 而人工紫胶林虽具有积极作用, 但仍需进一步恢复。     

Primates in Human-Modified and Fragmented Landscapes: The Conservation Relevance of Modelling Habitat and Disturbance Factors in Density Estimation

Accurate density estimations of threatened animal populations is essential for management and conservation. This is particularly critical for species living in patchy and altered landscapes, as is the case for most tropical forest primates. In this study, we used a hierarchical modelling approach that incorporates the effect of environmental covariates on both the detection (i.e. observation) and the state (i.e. abundance) processes of distance sampling. We applied this method to already published data on three arboreal primates of the Udzungwa Mountains of Tanzania, including the endangered and endemic Udzungwa red colobus (Procolobus gordonorum). The area is a primate hotspot at continental level. Compared to previous, ‘canonical’ density estimates, we found that the inclusion of covariates in the modelling makes the inference process more informative, as it takes in full account the contrasting habitat and protection levels among forest blocks. The correction of density estimates for imperfect detection was especially critical where animal detectability was low. Relative to our approach, density was underestimated by the canonical distance sampling, particularly in the less protected forest. Group size had an effect on detectability, determining how the observation process varies depending on the socio-ecology of the target species. Lastly, as the inference on density is spatially-explicit to the scale of the covariates used in the modelling, we could confirm that primate densities are highest in low-to-mid elevations, where human disturbance tend to be greater, indicating a considerable resilience by target monkeys in disturbed habitats. However, the marked trend of lower densities in unprotected forests urgently calls for effective forest protection.     

Fragmented living: Behavioural ecology of primates in a forest fragment in the Lopé Reserve, Gabon

A 17-month study was made of the primates using a 9-ha “island” of forest, surrounded by savanna, in the northern part of the Lopé Reserve, Gabon. One group ofCercopithecus cephus (plus a young maleCercopithecus nictitans who was in permanent association with them) were resident in the fragment and groups of five other species of primates made visits during 127 days of observation:Pan troglodytes, 15 visits;Cercocebus albigena, 10;Colobus satanas, 3;Cercopithecus nictitans, 2;C. pogonias, 1. Visits were also made by lone males of three species,C. nictitans, Cercocebus albigena, andMandrillus sphinx. The eighth species of diurnal primate present at Lopé,Gorilla g. gorilla, did not visit the fragment during the study. Compared to conspecific groups in neighbouring continuous forest, primates in the fragment ate less fruit, seeds and flowers and more insects and leaves. The local population density of primates resident in the fragment was equivalent to that of the neighbouring continuous forest where all eight species occur, despite the diversity and abundance of fruit being less in the fragment. The costs imposed on the resident group by the reduced diversity and availability of preferred fruit foods appeared to be offset by a number of benefits that increased individual feeding efficiency for monkeys residing within a single fragment. These included lower travel costs, reduced feeding competition between individuals through group fission, and excellent knowledge of the location and quality of food resources in the small home range. It is also possible that the overall negative impact of inter-specific feeding competition was lower in fragments than in continuous forest and that micro-habitat differences resulted in an increased availability of palatable insect and leaf fallback foods in the fragment.     

塔里木荒漠河岸林不同生境群落物种多度分布格局

为解释塔里木荒漠河岸林群落构建和物种多度分布格局形成的机理, 本文以塔里木荒漠河岸林2个不同生境(沙地、河漫滩) 4 ha固定监测样地为研究对象, 基于两样地物种调查数据, 采用统计模型(对数级数模型、对数正态模型、泊松对数正态分布模型、Weibull分布模型)、生态位模型(生态位优先占领模型、断棍模型)和中性理论模型(复合群落零和多项式模型、Volkov模型)拟合荒漠河岸林群落物种多度分布, 并用K-S检验与赤池信息准则(AIC)筛选最优拟合模型。结果表明: (1)随生境恶化(土壤水分降低), 植物物种多度分布曲线变化减小, 群落物种多样性、多度和群落盖度降低, 常见种数减少。(2)选用的3类模型均可拟合荒漠河岸林不同生境群落物种多度分布格局, 统计模型和中性理论模型拟合效果均优于生态位模型。复合群落零和多项式模型对远离河岸的干旱沙地生境拟合效果最好; 对数正态模型和泊松对数正态模型对洪水漫溢的河漫滩生境拟合效果最优; 中性理论模型与统计模型无显著差异。初步推断中性过程在荒漠河岸林群落构建中发挥着主导作用, 但模型拟合结果只能作为推断群落构建过程的必要非充分条件, 不能排除生态位过程的潜在作用。     

Interspecific primate associations in Amazonian flooded and unflooded forests

Stable associations between two or more primate species are a prominent feature of neotropical forest vertebrate communities and many studies have addressed their prevalence, and their costs and benefits. However, little is known about the influence of different habitat types on the frequency, seasonality, and composition of mixed-species groups in Amazonian forest primates. Here we examine the features of interspecific primate groups in a large mosaic of flooded (várzea and igapó) and unflooded (terra firme) forest in central Amazonia. In total, 12 primate species occurred in the study area, nine of which were observed in mixed-species associations. Primates were more than twice as likely to form associations in várzea forest than in terra firme forest. Squirrel monkeys were most frequently found in mixed-species groups in all forest types, most commonly in association with brown capuchins. Another frequent member of interspecific associations was the buffy saki, which often formed mixed-species groups with tamarins or brown capuchins. There was no seasonality in the frequency of associations in terra firme forest whereas associations in várzea forest were twice as frequent during the late-dry and early-wet seasons than in the late-wet and early-dry seasons. Interspecific primate associations were common in all forest types, but the degrees to which different species associate varied between these environments. We suggest that the temporal variation of várzea forest associations is connected with seasonal changes in habitat structure and resource abundance. However, more work is needed to pinpoint the underlying causes of mixed-species associations in all forest types and their strong seasonality in várzea forest.