Primates play an important role in ecosystem functioning and offer critical insights into human evolution, biology, behavior, and emerging infectious diseases. There are 26 primate species in the Atlantic Forests of South America, 19 of them endemic. We compiled a dataset of 5,472 georeferenced locations of 26 native and 1 introduced primate species, as hybrids in the genera Callithrix and Alouatta. The dataset includes 700 primate communities, 8,121 single species occurrences and 714 estimates of primate population sizes, covering most natural forest types of the tropical and subtropical Atlantic Forest of Brazil, Paraguay and Argentina and some other biomes. On average, primate communities of the Atlantic Forest harbor 2 ± 1 species (range = 1–6). However, about 40% of primate communities contain only one species. Alouatta guariba (N = 2,188 records) and Sapajus nigritus (N = 1,127) were the species with the most records. Callicebus barbarabrownae (N = 35), Leontopithecus caissara (N = 38), and Sapajus libidinosus (N = 41) were the species with the least records. Recorded primate densities varied from 0.004 individuals/km2 (Alouatta guariba at Fragmento do Bugre, Paraná, Brazil) to 400 individuals/km2 (Alouatta caraya in Santiago, Rio Grande do Sul, Brazil). Our dataset reflects disparity between the numerous primate census conducted in the Atlantic Forest, in contrast to the scarcity of estimates of population sizes and densities. With these data, researchers can develop different macroecological and regional level studies, focusing on communities, populations, species co‐occurrence and distribution patterns. Moreover, the data can also be used to assess the consequences of fragmentation, defaunation, and disease outbreaks on different ecological processes, such as trophic cascades, species invasion or extinction, and community dynamics. There are no copyright restrictions. Please cite this Data Paper when the data are used in publications. We also request that researchers and teachers inform us of how they are using the data.

The feeding behavior of a group of titis (Callicebus coimbrai) was monitored over an annual cycle at a site in northeastern Brazil. Behavioral data were collected in scan samples (1-min scan at 5-min intervals), and complementary data on fruit availability and new leaf cover were collected. Feeding time accounted for 28.9% of daily activity. Fruit was the principal item of the diet (61.2% of records) and the primary category in all months except September, when it was surpassed by leaves. Young leaves were the second most important category (20.0%). The consumption of seeds and insects was prominent in November and December. Fifty-two plant species were exploited, and the Elaeocarpaceae, Myrtaceae, Sapotaceae, and Passifloraceae provided the vast majority (86.0%) of plant feeding records. The phenological record did not provide a good measure of fruit availability, but a strong correlation (r(s) =0.902, P<0.0001, n=12) was found between the consumption of leaves and the exploitation of lianas each month. Lianas accounted for 28.2% of plant feeding records, and predominated between August and December. This suggests that lianas may represent a key factor in the ability of the species to tolerate the intense habitat fragmentation found throughout its geographic range.

Anthropogenic habitat fragmentation is a chronic problem throughout the Brazilian Atlantic Forest biome. In the present study, four forest fragments of 60-120 ha were surveyed on a rural property in southern Sergipe, where two endangered primate species, Callicebus coimbrai Kobayashi & Langguth, 1999 and Cebus xanthosternos Wied-Neuwied, 1826, are found. Two transects were established in each fragment, and the predominant habitat in 50 m sectors was assigned to one of three categories (mature forest, secondary forest and anthropogenic forest). Standard line transect surveys of the resident primate populations - which included a third species, Callitrhix jacchus Linnaeus, 1758 - were conducted, with a total of 476 km walked transect, resulting in 164 primate sightings. At each sighting of a primate, the habitat class was recorded and the height of the individual above the ground was estimated. The analysis indicated a significant (p < 0.05) preference for mature forest in C. xanthosternos which was also observed more frequently in the larger and better preserved fragments. No clear habitat preference was verified in the other two species, although both were relatively more abundant in the smaller fragments. However, a tendency to avoid anthropogenic forest was observed in C. coimbrai. Callitrhix jacchus used significantly lower (p < 0.05) forest strata than the other species, although other differences were unclear, presumably because of the reduced stature of the forest in the fragments. Overall, the results of the study indicate that C. xanthosternos is tolerant of the effects of habitat fragmentation, and that differential habitat use may play an important role in niche partitioning

Line transect surveying is a relatively rapid and efficient procedure for the assessment of primate populations; although the reliability of the resulting density estimates is affected by a number of factors, including habitat configuration. In this study, primate populations were surveyed at a highly fragmented site in northeastern Brazil, where the resident species include the endangered Coimbra-Filho's titi, Callicebus coimbrai, and the critically endangered yellow-breasted capuchin, Cebus xanthosternos. In addition to standard line transect surveys, data were collected on the composition and distribution of resident groups during playback surveys and ecological monitoring. During surveys, a 5.3-km trail system was walked regularly over a 7-month period, accumulating a total transect length of 476 km and 104 sightings of Callicebus and 41 of Cebus (as well as 19 records of a third primate, Callithrix jacchus). Data were analyzed using the DISTANCE program and the Kelker method, using the perpendicular distances to first animal sighted. Estimates of group density were highly discrepant from known values for both species; although in the case of Cebus, this seemed to reflect grouping patterns at the site. For Callicebus, population density was overestimated considerably when known group counts were used. Overall, there seems to be a need for a much more rigorous standardization of procedures, and the analysis and presentation of results, in order to guarantee the most reliable interpretation possible of the data. These considerations are especially important in the case of endangered species, such as those studied here.

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.