Guenon Species Research Articles

Current social management practices contribute to reproductive failure in zoo-housed guenons

Recent emphasis on reflecting natural behaviour and wild group composition in zoo-housed social animals has resulted in substantial improvement in captive breeding and welfare. We investigated studbook data for four guenon species housed in European zoos to assess the role of zoo management practices in the reproductive success of social species. We hypothesized that group dynamics reflecting wild living, including early social experience, would be associated with greater reproductive success. Our findings are presented in a standardized qualitative risk assessment with an additional certainty measure in the form of literature evidence. We found that greater reproductive success was associated with more potential breeding partners in L’Hoest’s, Roloway and Diana monkeys and with larger group sizes in all species studied here, providing support that mimicking wild group size, composition, and dynamics under captive conditions can improve reproductive success. Unexpectedly, greater reproductive success was associated with earlier first inter-facility transfers in female L’Hoest’s and Diana monkeys, and with more frequent inter-facility transfers in male L’Hoest’s and Diana monkeys. Furthermore, for male Diana monkeys and female and male L’Hoest’s monkeys, mothers with less reproductive and rearing experience tended to produce offspring that in turn had greater reproductive success, hinting at more complex and sex-differentiated mechanisms underlying sub-optimal reproduction in zoo guenons. Our findings highlight the importance of carrying out species-specific studies, and demonstrate that zoo management and husbandry practices can inadvertently impact reproductive success. We recommend that zoos holding guenons consider reducing the number of guenon species they hold in favour of increasing group size to improve reproductive success.

Complex Evolutionary History With Extensive Ancestral Gene Flow in an African Primate Radiation.

Understanding the drivers of speciation is fundamental in evolutionary biology, and recent studies highlight hybridization as an important evolutionary force. Using whole-genome sequencing data from 22 species of guenons (tribe Cercopithecini), one of the world's largest primate radiations, we show that rampant gene flow characterizes their evolutionary history and identify ancient hybridization across deeply divergent lineages that differ in ecology, morphology, and karyotypes. Some hybridization events resulted in mitochondrial introgression between distant lineages, likely facilitated by cointrogression of coadapted nuclear variants. Although the genomic landscapes of introgression were largely lineage specific, we found that genes with immune functions were overrepresented in introgressing regions, in line with adaptive introgression, whereas genes involved in pigmentation and morphology may contribute to reproductive isolation. In line with reports from other systems that hybridization might facilitate diversification, we find that some of the most species-rich guenon clades are of admixed origin. This study provides important insights into the prevalence, role, and outcomes of ancestral hybridization in a large mammalian radiation.

Camera Traps Uncover the Behavioral Ecology of an Endemic, Cryptic Monkey Species in the Congo Basin.

Guenons are the most diverse clade of African primates, and many species living within the core of the Congo Basin rainforest are still understudied. The recently described guenon species, Cercopithecus lomamiensis, known as lesula, is a cryptic, semi-terrestrial species endemic to the central Congo Basin in the Democratic Republic of the Congo. The recent IUCN Red List Assessment recognizes lesula's risk of extinction in the wild as Vulnerable. The objective of our study was to use camera traps to expand knowledge on the behavioral ecology of lesula. We conducted three systematic, terrestrial camera trap (CT) surveys within Lomami National Park and buffer zone (Okulu: 2013; Losekola: 2014; E15: 2015). We accumulated 598 independent events of lesula over 5960 CT days from 92 CTs. Typical of Cercopithecus species, camera trap videos reveal that lesula has a diurnal activity pattern, birth seasonality, a group size of up to 32 individuals, and social organization with female philopatry and male dispersal. Results also suggest that lesula are highly terrestrial, distinguishing them from other Cercopithecus species, which are mostly arboreal. Our study provides new information about the behavioral ecology of this little-studied primate, generating species-specific knowledge of a threatened species for successful conservation planning.

Oral Processing of Three Guenon Species in Taï National Park, Côte d'Ivoire.

Three guenon species in Taï National Park frequently form and maintain stable polyspecific associations despite significant feeding competition. This dietary overlap provides an opportunity to examine how closely related and anatomically similar taxa process the same foods. Our research examines whether the oral-processing behaviors of these guenons differ when they consume the same foods. Methods: Data on oral-processing behavior were collected on one habituated group each of Cercopithecus campbelli, C. diana, and C. petaurista in Taï National Park, Côte d'Ivoire from January 2016 to December 2018. We recorded the frequency with which foods were introduced to the mouth (ingestive action) and the frequency with which foods were processed using incisors, canines, and postcanine teeth. Oral-processing profiles for species-specific plant foods, fungi, and invertebrates were compared using Monte Carlo resampling. We quantified oral-processing behavior during a total of 2316 five-minute focal periods. Diana monkeys use their incisors significantly more per ingestive action than Campbell's monkeys or Lesser spot-nosed guenons. Lesser spot-nosed guenons use their incisors more than Campbell's monkeys. Diana monkeys also use significantly more post-canine chews per ingestive action than Campbell's monkeys and Lesser spot-nosed guenons. Lesser spot-nosed guenons generally use fewer post-canine chews than Diana monkeys but more than Campbell's monkeys. Canine use during feeding was rare in all three taxa. The three study species use different oral-processing profiles when consuming the same foods. These results are intriguing given the overall similarity in dental and cranial anatomy in these taxa. The oral-processing profiles we report do not encompass the full dietary breadth of all species; however, the behavioral diversity demonstrated during consumption of the same foods suggests that insight into feeding behavior is more likely obtained by examining oral processing of individual foods rather than broad food categories. Furthermore, these results underscore that important variation in feeding behavior is not necessarily associated with morphological differences in dental or craniofacial anatomy.

Population dynamics of the Manyara monkey (Cercopithecus mitis manyaraensis) and vervet monkey (Chlorocebus pygerythrus) in Lake Manyara National Park, Tanzania.

Estimating population densities and their trends over time is essential for understanding primate ecology and for guiding conservation efforts. From 2011 through to 2019, we counted two guenon species during seasonal road transect surveys in Lake Manyara National Park: the Tanzania-endemic Manyara monkey Cercopithecus mitis manyaraensis (International Union for Conservation of Nature and Natural Resources, IUCN, Red List category of "endangered") and the vervet monkey Chlorocebus pygerythrus (Red List category of "least concern"). To account for imperfect detectability, we analysed the data in a line distance sampling framework, fitted species-specific detection functions, and subsequently estimated seasonal densities. To test for seasonal differences and yearly trends in the species-specific density estimates, we fitted generalized additive models. Seasonal point density estimates fluctuated considerably during the 9years (2011-2019) of our study, ranging from 3 to 29 individuals km for Manyara monkeys and from 19 to 83 individuals km for vervet monkeys. Densities of both taxa did not differ seasonally, and we did not detect marked directional population trends. Our study illustrates the utility and limitations of line distance sampling for long-term primate monitoring. Beyond informing primate ecology and management, our results highlight the conservation importance of Lake Manyara National Park for primate conservation.

Occam's razor revisited: guenon species morphology supports evidence for an African influence in Bronze Age Aegean fresco primate iconography from Akrotiri, Thera.

In a recent exchange, Pareja et al. (Primates 61: 159-168, 2020a; Primates 61: 767-774, 2020b) and Urbani and Youlatos (Primates, https://doi.org/10.1007/s10329-020-00825-2 , 2020a) dispute the re-interpretation of the primate species depicted in a Bronze Age fresco from Room 6 of Building Complex Beta at Akrotiri, Thera. They review the history of interpretations of this artwork and combine the expertise of scholars that traditionally focus on such research with the scientific expertise of primatologists to reexamine the artwork. Additionally, they emphasize the morphological traits exhibited by these painted primates. We review and expand their list of candidate primates here in a decision table to demonstrate that the African link is better supported by the morphological traits than the Asian one proposed by Pareja et al. (2020a, b). Using such evidence, we show that other guenons of the tribe Cercopithecini, such as L'Hoest's monkey (Allochrocebus lhoesti) and the Diana monkey (Cercopithecus diana), provide equal support for the African link as the vervet monkey proposed by Urbani and Youlatos (2020a). However, the historical context supports the traditional interpretation that the Akrotiri fresco depicts vervet monkeys from this region. This discourse provides an open forum for scholars in various fields to contribute to an important problem that crosses disciplinary boundaries.

Skeletal morphology of the lesula (Cercopithecus lomamiensis) and the evolution of guenon locomotor behavior.

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. 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 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. 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.

The structure of species discrimination signals across a primate radiation.

Discriminating conspecifics from heterospecifics can help avoid costly interactions between closely related sympatric species. The guenons, a recent primate radiation, exhibit high degrees of sympatry and form multi-species groups. Guenons have species-specific colorful face patterns hypothesized to function in species discrimination. Here, we use a machine learning approach to identify face regions most essential for species classification across fifteen guenon species. We validate these computational results using experiments with live guenons, showing that facial traits critical for accurate classification influence selective attention toward con- and heterospecific faces. Our results suggest variability among guenon species in reliance on single-trait-based versus holistic facial characteristics for species discrimination, with behavioral responses and computational results indicating variation from single-trait to whole-face patterns. Our study supports a role for guenon face patterns in species discrimination, and shows how complex signals can be informative about differences between species across a speciose and highly sympatric radiation.

Time Constraints Do Not Limit Group Size in Arboreal Guenons but Do Explain Community Size and Distribution Patterns

To understand how species will respond to environmental changes, it is important to know how those changes will affect the ecological stress that animals experience. Time constraints can be used as indicators of ecological stress. Here we test whether time constraints can help us understand group sizes, distribution patterns, and community sizes of forest guenons (Cercopithecus/Allochrocebus). Forest guenons typically live in small to medium sized one-male–multifemale groups and often live in communities with multiple forest guenon species. We developed a time-budget model using published data on time budgets, diets, body sizes, climate, and group sizes to predict maximum ecologically tolerable group and community sizes of forest guenons across 202 sub-Saharan African locations. The model correctly predicted presence/absence at 83% of these locations. Feeding-foraging time (an indicator of competition) limited group sizes, while resting and moving time constraints shaped guenon biogeography. Predicted group sizes were greater than observed group sizes but comparable to community sizes, suggesting community sizes are set by competition among guenon individuals irrespective of species. We conclude that time constraints and intraspecific competition are unlikely to be the main determinants of relatively small group sizes in forest guenons. Body mass was negatively correlated with moving time, which may give larger bodied species an advantage over smaller bodied species under future conditions when greater fragmentation of forests is likely to lead to increased moving time. Resting time heavily depended on leaf consumption and is likely to increase under future climatic conditions when leaf quality is expected to decrease.

Mitochondrial DNA Analyses of Cercopithecus Monkeys Reveal a Localized Hybrid Origin for C. mitis doggetti in Gombe National Park, Tanzania

In recent years, hybridization has gained recognition as an important creative force in primate evolution. The exchange of genetic material between species provides genetic novelty on which evolutionary forces, such as natural selection, may act. The guenon radiation (Tribe Cercopithecini) is known for numerous cases of contemporary hybridization—in the wild and captivity—between broadly sympatric species. Interspecific hybrids are viable, and field studies report fertile hybrid females. Despite being a well-documented phenomenon, hybridization among wild guenons is relatively rare and sporadic. An exception is the long-standing hybridization between Cercopithecus mitis doggetti and C. ascanius schmidti in Gombe National Park, Tanzania, where hybrids comprise a significant proportion of the breeding population. Here, I used mitochondrial loci to conduct a genetic survey of the Gombe population and examine the extent and direction of gene flow between the parental species. I extracted DNA from noninvasive fecal samples of unhabituated individuals (N = 144 individuals) with known phenotype and provenance. All parental phenotypes and hybrid individuals were identified in the field based on species specific pelage colors and patterns. Phylogenetic analyses of DNA sequences from inside and outside the hybrid zone show Gombe’s population of C. mitis doggetti is distinct from neighboring conspecific populations in having mitochondrial DNA of C. ascanius schmidti. All animals surveyed from the hybrid zone have one of two haplotypes of C. ascanius schmidti unique to Gombe. These results provide evidence of asymmetric introgressive hybridization between sympatric guenon species, a likely consequence of colonization patterns of the parental species during range expansions. The spatial distribution patterns of the two haplotypes imply that Gombe is a site of both historic and contemporary hybridization between sympatric guenons. The discovery of gene flow and ongoing hybridization between clearly defined species, ecologically distinct enough to coexist in broad sympatry, provides an ideal system to investigate speciation mechanisms in primate adaptive radiations.

Dietary Variation in Diana Monkeys (Cercopithecus diana): The Effects of Polyspecific Associations

Establishing dietary central tendencies and extremes remains an important goal of primate research. While habitat differences and spatial discontinuity are well-documented contributors to dietary variation, other factors including polyspecific associations may significantly impact diet through changes in strata use and/or increased feeding competition. Here, we examine polyspecific association with closely related species as a source of dietary variation in a rain forest primate. Diana monkeys (Cercopithecus diana) in Côte d'Ivoire's Taï Forest frequently participate in mixed-species groups. We use data collected over a 5-year period on 4 Diana monkey groups to examine how association affects group diets. Groups exhibited significant differences in association rates with other guenon species, but this minimally influenced diet when food categories (fruit, invertebrates, leaves) were compared: diet overlap of 4 groups across the study period ranges from 90.8 to 98.1%. Examination of species composition within food categories is more revealing: intergroup dietary overlap decreases to 69.8-79.4% across the study period when comparing species contributing to total frugivory and folivory. These data support earlier findings that Diana monkeys maintain fruit-rich diets by competitively excluding sympatric congeners while highlighting that even selective frugivores such as Diana monkeys may exhibit remarkable dietary flexibility. Our study underscores the fact that broad categorical labels can obscure significant dietary differences.

Phyloepidemiological Analysis Reveals that Viral Divergence Led to the Paucity of Simian Immunodeficiency Virus SIVmus/gsn/mon Infections in Wild Populations.

ABSTRACTHuman immunodeficiency virus type 1 (HIV-1) is the result of cross-species transmission of simian immunodeficiency virus from chimpanzees (SIVcpz). SIVcpz is a chimeric virus which shares common ancestors with viruses infecting red-capped mangabeys and a subset of guenon species. The epidemiology of SIV infection in hominoids is characterized by low prevalences and an uneven geographic distribution. Surveys in Cameroon indicated that two closely related members of the guenon species subset, mustached guenons and greater spot-nosed guenons, infected with SIVmus and SIVgsn, respectively, also have low rates of SIV infections in their populations. Compared to that for other monkeys, including red-capped mangabeys and closely related guenon species, such an epidemiology is unusual. By intensifying sampling of geographically distinct populations of mustached and greater spot-nosed guenons in Gabon and including large sample sets of mona guenons from Cameroon, we add strong support to the hypothesis that the paucity of SIV infections in wild populations is a general feature of this monophyletic group of viruses. Furthermore, comparative phylogenetic analysis reveals that this phenotype is a feature of this group of viruses infecting phylogenetically disparate hosts, suggesting that this epidemiological phenotype results from infection with these HIV-1-related viruses rather than from a common host factor. Thus, these HIV-1-related viruses, i.e., SIVcpz and the guenon viruses which share an ancestor with part of the SIVcpz genome, have an epidemiology distinct from that found for SIVs in other African primate species.IMPORTANCE Stable virus-host relationships are established over multiple generations. The prevalence of viral infections in any given host is determined by various factors. Stable virus-host relationships of viruses that are able to cause persistent infections and exist with high incidences of infection are generally characterized by a lack of morbidity prior to host reproduction. Such is the case for cytomegalovirus (CMV) and Epstein-Barr virus (EBV) infections of humans. SIV infections of most African primate species also satisfy these criteria, with these infections found at a high prevalence and with rare cases of clinical disease. In contrast, SIVcpz, the ancestor of HIV-1, has a different epidemiology, and it has been reported that infected animals suffer from an AIDS-like disease in the wild. Here we conclusively demonstrate that viruses which are closely related to SIVcpz and infect a subset of guenon monkeys show an epidemiology resembling that of SIVcpz.

Effects of Farming Activities on the Population of Three Sympatric Species of Guenons in Afi Mountain Wildlife Sanctuary, Cross River State, Nigeria

Effects of Farming Activities on the Population of Three Sympatric Species of Guenons in Afi Mountain Wildlife Sanctuary, Cross River State, Nigeria

Sniffing Behaviours in Guenons

In Old World monkeys (OWM), the olfactory sense is thought to be less important than in other primate taxa. However, during the last decade experimental studies have shown that OWM possess much better olfactory capabilities than suspected. Here, we investigate for the very first time sniffing behaviours in three guenon species (Diana, de Brazza's and owl-faced monkeys) held in the Leipzig Zoo, Germany. We recorded frequencies and contexts of sniffing. The sniff index was used to allow comparisons across species. It was found that individuals sniffed 6.12 ± 7.69 times per hour. Most sniffing occurred in food-related contexts. Furthermore, Diana monkeys sniffed less often than de Brazza's and owl-faced monkeys. Thus, natural selection may drive the differences in using the olfactory sense in closely related primate species.

Discovery and full genome characterization of a new SIV lineage infecting red-tailed guenons (Cercopithecus ascanius schmidti) in Kibale National Park, Uganda

BackgroundHuman immunodeficiency virus (HIV) type 1 and 2, the causative agents of acquired immunodeficiency syndrome (AIDS), emerged from African non-human primates (NHPs) through zoonotic transmission of simian immunodeficiency viruses (SIV). Among African NHPs, the Cercopithecus genus contains the largest number of species known to harbor SIV. However, our understanding of the diversity and evolution of SIVs infecting this genus is limited by incomplete taxonomic and geographic sampling, particularly in East Africa. In this study, we screened blood specimens from red-tailed guenons (Cercopithecus ascanius schmidti) from Kibale National Park, Uganda, for the presence of novel SIVs using unbiased deep-sequencing.FindingsWe describe and characterize the first full-length SIV genomes from wild red-tailed guenons in Kibale National Park, Uganda. This new virus, tentatively named SIVrtg_Kib, was detected in five out of twelve animals and is highly divergent from other Cercopithecus SIVs as well as from previously identified SIVs infecting red-tailed guenons, thus forming a new SIV lineage.ConclusionsOur results show that the genetic diversity of SIVs infecting red-tailed guenons is greater than previously appreciated. This diversity could be the result of cross-species transmission between different guenon species or limited gene flow due to geographic separation among guenon populations.

Character displacement of Cercopithecini primate visual signals.

Animal visual signals have the potential to act as an isolating barrier to prevent interbreeding of populations through a role in species recognition. Within communities of competing species, species recognition signals are predicted to undergo character displacement, becoming more visually distinctive from each other, however this pattern has rarely been identified. Using computational face recognition algorithms to model primate face processing, we demonstrate that the face patterns of guenons (tribe: Cercopithecini) have evolved under selection to become more visually distinctive from those of other guenon species with whom they are sympatric. The relationship between the appearances of sympatric species suggests that distinguishing conspecifics from other guenon species has been a major driver of diversification in guenon face appearance. Visual signals that have undergone character displacement may have had an important role in the tribe’s radiation, keeping populations that became geographically separated reproductively isolated on secondary contact.

Age‐ and sex‐specific patterns of vocal behavior in De Brazza's monkeys (Cercopithecus neglectus)

Although vocal production is strongly genetically determined in nonhuman primates, vocal usage is more likely to be influenced by experience. Nonetheless, sex differences in both production and usage can be found in the vocal repertoire of adults, but little attention has been paid to their ontogeny. Here, we provide the first comprehensive analysis of the vocal repertoire of De Brazza's monkeys (Cercopithecus neglectus), with particular attention to age- and sex-specific patterns. This species has special interest because it is the only monogamous species of guenons, but it nevertheless shares the strong sexual morphological and behavioral dimorphism seen in other guenons. A structurally based classification of calls recorded in 23 captive individuals has been cross-validated by an analysis of the associated contexts of emission. We identified sound units that could be uttered alone or concatenated to form 10 call types, including only three types shared by all age-sex-classes. Both age- and sex-discrepancy in terms of phonation could be explained by maturational changes and morphological dimorphism. In general, call production and usage parallel those seen in other guenons, suggesting that phylogeny and sexual dimorphism play important roles in vocal communication in this species. However, the boundary between adult male and female vocal repertoires appeared to be less strict than previously reported, suggesting that both sexes have the capacity to produce calls of the other sex but that social roles may constrain this expression. Similarly, age-specific vocal patterns would reflect respective social roles, and experience to some extent. Finally, calling rates would reflect age-/sex-specific degree of involvement in intragroup social networks. These findings highlight the relative importance of phylogeny, morphology, and social system on the shaping of individual repertoires in nonhuman primates.

Lack of Evidence of Simian Immunodeficiency Virus Infection Among Nonhuman Primates in Taï National Park, Côte d’Ivoire: Limitations of Noninvasive Methods and SIV Diagnostic Tools for Studies of Primate Retroviruses

It is now well established that the human immunodeficiency viruses, HIV-1 and HIV-2, are the results of cross-species transmissions of simian immunodeficiency viruses (SIV) naturally infecting nonhuman primates in sub-Saharan Africa. SIVs are found in many African primates, and humans continue to be exposed to these viruses by hunting and handling primate bushmeat. Sooty mangabeys (Cercocebus atys) and western red colobus (Piliocolobus badius badius) are infected with SIV at a high rate in the Taï Forest, Côte d'Ivoire. We investigated the SIV infection and prevalence in 6 other monkey species living in the Taï Forest using noninvasive methods. We collected 127 fecal samples from 2 colobus species (Colobus polykomos and Procolobus verus) and 4 guenon species (C. diana, C. campbelli, C. petaurista, and C. nictitans). We tested these samples for HIV cross-reactive antibodies and performed reverse transcriptase-polymerase chain reactions (RT-PCR) targeting the gag, pol, and env regions of the SIV genome. We screened 16 human microsatellites for use in individual discrimination and identified 4-6 informative markers per species. Serological analysis of 112 samples yielded negative (n=86) or uninterpretable (n=26) results. PCR analysis on 74 samples confirmed the negative results. These results may reflect either the limited number of individuals sampled or a low prevalence of infection. Further research is needed to improve the sensitivity of noninvasive methods for SIV detection.

Combining Biogeographic and Phylogenetic Data to Examine Primate Speciation: An Example Using Cercopithecin Monkeys

ABSTRACTWe combined phylogenetic and biogeographic data to examine the mode of speciation in a group of African monkeys, the Cercopithecini. If allopatric speciation is the major force producing species, then there should be a positive relationship between the relative divergence time of taxa and their degree of geographic range overlap. Alternatively, an opposite relationship between divergence time and geographic range overlap is consistent with sympatric speciation as the main mechanism underlying the cercopithecin radiation. We collected biogeographic and phylogenetic data for 19 guenon species from the literature. We digitized geographic range maps and utilized three different phylogenetic hypotheses based on Y chromosome, X chromosome, and mitochondrial (mtDNA) data. We used regressions with Monte Carlo simulation to examine the relationship between the relative time since divergence of taxa and their degree of geographic range overlap. We found that there was a positive relationship between relative divergence time and the proportion of geographic range overlap between taxa using all three molecular data sets. Our findings provide evidence for allopatric speciation being the common mode of diversification in the cercopithecin clade. Because most of these primates are forest adapted mammals, the cyclical contraction and expansion of African forests from the late Miocene to the present has likely been an important factor driving allopatric speciation. In addition, geographic barriers such as the Congo and Sanaga rivers have probably played a complementary role in producing new species within the clade.

Relatedness and Social Behaviors in Cercopithecus solatus

Inclusive fitness and kin selection theories predict that organisms will evolve biased behavior toward kin when the inclusive fitness benefits outweigh the costs of such behaviors. Researchers have long observed that primates bias their behavior toward relatives, particularly maternal kin. We examined the effect of kinship on social behaviors in a semifree-ranging colony of Cercopithecus solatus, a poorly studied forest guenon species. We used microsatellite loci and paternity analyses to determine the degree of relatedness between individuals, as well as kinship. Individuals biased some of their behavior according to relatedness. Specifically, related individuals are more spatially associated and less aggressive toward each other. When we replaced the relatedness coefficients with defined kin categories, Cercopithecus solatus seemed to behave preferentially toward maternal kin versus paternal kin. Even though the setting of the colony and the small sample size limit our conclusions, we discuss the potential implications of our finding for the study of the impact of kin selection in primate social relationships.