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The natural history and taxonomic status of two central African primates, Cercopithecus dryas and Cercopithecus salongo have long been in question. Recent studies confirmed that C. dryas is a basal member of the savanna monkey clade, and that it prefers dense undergrowth in lowland rainforest. While these studies advanced our knowledge of this enigmatic species, key aspects of its natural history remain poorly documented. Furthermore, the lack of a field study that documents pelage patterns of both sexes and different age classes of C. dryas has led to a disagreement over the validity of C. salongo as a sister taxon to C. dryas. Using the results of two multi-strata camera trap surveys in Lomami National Park (Democratic Republic of the Congo) and its buffer zone, we conducted a third survey in the understory of degraded forest to accumulate videos of C. dryas/salongo. We used these videos to test the hypothesis that C. dryas and C. salongo are synonymous, and to assess the species' group composition, density, behavior and vocalizations. Camera traps revealed an ontogenetic change in pelage pattern that supports the view that C. salongo is the adult of C. dryas. Videos revealed that adult males develop a blue perineum and scrotum, and a red subcaudal patch, similar to other savanna monkeys. We provide a preliminary assessment of C. dryas' group composition, density, behavior, and vocalizations. This long-overlooked monkey is an exceptional member of the Chlorocebus clade, and all aspects of its biology require further investigation., (© 2021 Wiley Periodicals LLC.)

Objectives: The guenons (tribe Cercopithecini) are a diverse and primarily arboreal radiation of Old World monkeys from Africa. However, preliminary behavioral observations of the lesula (Cercopithecus lomamiensis), a little-known guenon species described in 2012, report it spending substantial amounts of time on the ground. New specimens allow us to present the first description of lesula postcranial morphology and apply a comparative functional morphology approach to supplement our knowledge of its locomotor behavior., Materials and Methods: To infer the substrate use preferences of the lesula, 22 postcranial variables correlated with locomotion were assessed in a sample of 151 adult guenon specimens, including two C. lomamiensis. Using multivariate statistical analyses, we predict the amount of time the lesula spends on the ground relative to the comparative sample., Results: Results suggest that the lesula spends nearly half its time on the ground, and the two available individuals were classified as semiterrestrial and terrestrial with strong support. Comparisons with two outgroup cercopithecid taxa (Colobus guereza and Macaca mulatta) demonstrate that, as a group, guenons retain signals of a generalized, semiterrestrially adapted postcranium compared to specialized arboreal cercopithecids., Discussion: These results corroborate preliminary behavioral observations of the lesula as a semiterrestrial to terrestrial primate and imply multiple evolutionary transitions in substrate use among the guenon radiation. A broader view of cercopithecoid evolution suggests that a semiterrestrial ancestor for extant guenons is more parsimonious than an arboreal one, indicating that the arboreal members of the group are probably recently derived from a more semiterrestrial ancestor., (© 2020 Wiley Periodicals, Inc.)

In June 2007, a previously undescribed monkey known locally as "lesula" was found in the forests of the middle Lomami Basin in central Democratic Republic of Congo (DRC). We describe this new species as Cercopithecus lomamiensis sp. nov., and provide data on its distribution, morphology, genetics, ecology and behavior. C. lomamiensis is restricted to the lowland rain forests of central DRC between the middle Lomami and the upper Tshuapa Rivers. Morphological and molecular data confirm that C. lomamiensis is distinct from its nearest congener, C. hamlyni, from which it is separated geographically by both the Congo (Lualaba) and the Lomami Rivers. C. lomamiensis, like C. hamlyni, is semi-terrestrial with a diet containing terrestrial herbaceous vegetation. The discovery of C. lomamiensis highlights the biogeographic significance and importance for conservation of central Congo's interfluvial TL2 region, defined from the upper Tshuapa River through the Lomami Basin to the Congo (Lualaba) River. The TL2 region has been found to contain a high diversity of anthropoid primates including three forms, in addition to C. lomamiensis, that are endemic to the area. We recommend the common name, lesula, for this new species, as it is the vernacular name used over most of its known range.

The Ituri Forest, Democratic Republic of Congo (formerly Zaire) is an example of a closed canopy forest showing extreme depletion in (13)C. delta(13)C values for plants from the canopy top, from gaps in the canopy, and from the subcanopy average -29.0+/-1.7 per thousand, -30.4+/-0.9 per thousand, and -34.0+/-1.5 per thousand, respectively. The delta(13)C of forest mammals show these differences, with the subcanopy browsers (okapi, dwarf antelope) having delta(13)C values for tooth enamel much more negative than subcanopy frugivores who derive their food from the canopy top, and from folivores and omnivores living in gap or clearing areas. Nitrogen isotopes in plants from this ecosystem have an average delta(15)N value of 5.4+/-1.8 per thousand and do not show significant differences at the 95% confidence interval between plants from the canopy top, from gaps in the canopy, and from the subcanopy. The delta(18)O(SMOW) values of surface waters in the study area are between -2.0 and -2.7. The delta(18)O(PDB) for tooth enamel ranged from -3 to +7 per thousand.