Fossil Cercopithecidae from the Early Pliocene Sagantole Formation at Gona, Ethiopia.

The Early Pliocene Sagantole Fm. in the Gona Project area, Afar State, Ethiopia, is noted for discoveries of the early hominin Ardipithecus ramidus. A large series of fossil cercopithecid primates dated to between 4.8 and 4.3 Ma has also been collected from these sediments. In this paper, we use qualitative analysis and standard dental and postcranial measures to systematically describe the craniodental remains and tentatively allocate postcrania to taxa where we are able to. We then use these data to compare these specimens to fossil assemblages from contemporary sites, interpret their paleobiology, and discuss implications for the paleoecology of the Gona Sagantole Fm. We recognize three cercopithecid species in the Gona Sagantole Fm. Pliopapio alemui makes up approximately two-thirds of the identifiable specimens; nearly all of the rest are allocated to Kuseracolobus aramisi, and a single molar indicates the presence of a second, somewhat larger but morphologically distinct papionin. Among the Early Pliocene cercopithecids from Gona are also a number of postcranial elements. None of the postcranial remains are directly associated with any of the cranial material. Nonetheless, some of the distal humeri and proximal femora can be tentatively allocated to either Pl. alemui or K. aramisi based on a combination of size, as the latter is approximately 50% larger than the former, and morphology. If these assignments are correct, they suggest K. aramisi was primarily arboreal and similar to most extant colobines, whereas Pl. alemui was more mixed in its substrate use, being more terrestrially adapted than K. aramisi, but less so than extant Papio or Theropithecus. Thus, we interpret the predominance of Pl. alemui over K. aramisi is consistent with a somewhat more open environment at Gona than at Aramis.

Does Oxygen Stable Isotope Composition in Primates Vary as a Function of Vertical Stratification or Folivorous Behaviour?

Stable isotopes of oxygen often vary within a community of primates. For example, folivorous monkeys that forage in the upper reaches of the forest canopy tend to evince high δ18O values, whereas those that prefer the understory tend to have lower δ18O values. Given that leaves also have high δ18O values, particularly higher in the canopy, there is uncertainty as to which behavioural variable - vertical stratification or folivory - is the primary determinant of variation in δ18O values. Here, we explore further δ18O values from the Taï Forest monkeys (n = 7 species; n = 33 individuals) by examining the interaction between diet and vertical stratification, thereby allowing us to differentiate the effects of each covariate. We found that δ18O values varied as a function of mean canopy height, but not folivory, resolving uncertainty about the primary cause of δ18O variation. This outcome revolves largely, but not entirely, on the behaviours of Procolobus verus, a highly folivorous but understory forager. Relatively elevated values in Cercopithecus diana, a frugivorous but middle-to-high canopy forager, raises the possibility that plant reproductive tissues (e.g., fruits, flowers) may be increasingly sensitive to evaporative fractionation at higher forest canopy levels. Overall, our results further affirm the value of using δ18O values to estimate the vertical behaviour of primate species in a fossil assemblage.

Long bone structural proportions and locomotor behavior in Cercopithecidae.

Limb bone articular and diaphyseal proportions have been shown to relate to locomotor behavior in broad comparisons across catarrhines, but comparisons among phylogenetically and functionally more closely related species may be particularly useful in investigating form-function relationships that can be applied to fossil taxa. Here we compare inter- and intra-limb proportions of diaphyseal strength and articular surface area and breadth of the femur and humerus with frequencies of leaping and vertical climbing behavior in 13 cercopithecid species. Leaping frequency is highly positively correlated with femoral/humeral diaphyseal strength, moderately positively correlated with femoral/humeral articular breadth, and less highly correlated with femoral/humeral articular surface area. These results are consistent with predicted higher bending loads as well as joint reaction forces on the femora of leapers. Surface areas may show a weaker association because they also directly impact joint excursion and are thus more influenced by other aspects of locomotion, including climbing. Climbing frequency is positively correlated with humeral head articular surface area/diaphyseal strength, but weakly negatively correlated with femoral head articular surface area/diaphyseal strength. These combined trends lead to a strong negative association between climbing and femoral/humeral head surface area. Femoral/humeral diaphyseal strength and distal articular breadth are not correlated with climbing frequency. The climbing results are consistent with greater shoulder mobility in more frequent vertical climbers. The lack of such a relationship in the femur among these taxa contrasts with earlier findings for catarrhines more generally, including hominoids, and may be a result of different climbing kinematics in cercopithecoids involving less hip abduction than in hominoids. Different use of the forelimb during climbing in cercopithecoids and hominoids may also explain the lack of association between femoral/humeral diaphyseal strength and climbing in the present study, in contrast to comparisons across catarrhines more generally.

A window into the early evolutionary history of Cercopithecidae: Late Miocene evidence from Chad, Central Africa.

Central Africa is known as a major center of diversification for extant Old World Monkeys (OWM) and yet has a poorly documented fossil record of monkeys. Here we report a new colobine monkey (Cercopithecoides bruneti sp. nov.) from the Central African hominin-bearing fossiliferous area of Toros-Menalla, Chad at ca. 7 Ma. In addition to filling a gap in the spatial and temporal record of early OWM evolutionary history, we assess the ecomorphological diversity of early OWM by providing evidence on the onset of a folivorous diet and a partial reacquisition of terrestrial locomotor habits among Miocene colobines. We also support the phylogenetic affinities of the genus Cercopithecoides among the stem group of the extant African colobine monkeys.

Metagenomic analyses reveal previously unrecognized variation in the diets of sympatric Old World monkey species.

Insectivory, or the consumption of insects and other arthropods, is a significant yet cryptic component of omnivorous primate diets. Here, we used high-throughput DNA sequencing to identify arthropods from fecal DNA and assess variation in insectivory by closely-related sympatric primates. We identified arthropod prey taxa and tested the hypothesis that variation in insectivory facilitates niche differentiation and coexistence among closely-related species with high dietary overlap. We collected 233 fecal samples from redtail (Cercopithecus ascanius; n = 118) and blue monkeys (C. mitis; n = 115) and used a CO1 metabarcoding approach to identify arthropod DNA in each fecal sample. Arthropod DNA was detected in 99% of samples (N = 223 samples), and a total of 68 families (15 orders) were identified. Redtails consumed arthropods from 54 families, of which 12 (21.8%) were absent from blue monkey samples. Blue monkeys consumed arthropods from 56 families, of which 14 (24.6%) were absent from redtail samples. For both species, >97% of taxa present belonged to four orders (Araneae, Diptera, Hymenoptera, Lepidoptera). Redtail samples contained more Lepidoptera taxa (p<0.05), while blue monkey samples contained more Araneae (p<0.05). Blue monkeys consumed a greater diversity of arthropod taxa than redtail monkeys (p<0.05); however, the average number of arthropod families present per fecal sample was greater in the redtail monkey samples (p<0.05). These results indicate that while overlap exists in the arthropod portion of their diets, 20-25% of taxa consumed are unique to each group. Our findings suggest that variation in arthropod intake may help decrease dietary niche overlap and hence facilitate coexistence of closely-related primate species.

A Short Cut to Mushrooms - Red Langur (Presbytis rubicunda) Consumption of Terrestrial Fungus.

We report the first in-depth evidence of targeted mushroom foraging in an Asian colobine. Using direct observations (2010-2018) and camera traps (2008-2018) in the Sebangau Forest, Central Kalimantan, Indonesian Borneo, we show how adult female red langurs (Presbytis rubicunda) are regularly descending to the ground to consume mushrooms. We recorded 82 counts (0.36% of all focal observations, n = 25,502) of the focal adult langur on the ground from direct observations of habituated groups, and 80 independent images/videos of red langurs on the ground were obtained from the camera traps representing 1.12% of total images (n = 7,145). Mushroom consumption took place in 4 families, representing 0.04% of total focal behaviour observations and 24.3% of total time feeding on the ground. From the camera trap photos, red langurs are spending 20% of time on the ground feeding. We speculate that mushrooms could be a supplementary food for adult female langurs as there is an increase in consumption in April and November.

Wrist morphology reveals substantial locomotor diversity among early catarrhines: an analysis of capitates from the early Miocene of Tinderet (Kenya).

Considerable taxonomic diversity has been recognised among early Miocene catarrhines (apes, Old World monkeys, and their extinct relatives). However, locomotor diversity within this group has eluded characterization, bolstering a narrative that nearly all early catarrhines shared a primitive locomotor repertoire resembling that of the well-described arboreal quadruped Ekembo heseloni. Here we describe and analyse seven catarrhine capitates from the Tinderet Miocene sequence of Kenya, dated to ~20 Ma. 3D morphometrics derived from these specimens and a sample of extant and fossil capitates are subjected to a series of multivariate comparisons, with results suggesting a variety of locomotor repertoires were present in this early Miocene setting. One of the fossil specimens is uniquely derived among early and middle Miocene capitates, representing the earliest known instance of great ape-like wrist morphology and supporting the presence of a behaviourally advanced ape at Songhor. We suggest Rangwapithecus as this catarrhine's identity, and posit expression of derived, ape-like features as a criterion for distinguishing this taxon from Proconsul africanus. We also introduce a procedure for quantitative estimation of locomotor diversity and find the Tinderet sample to equal or exceed large extant catarrhine groups in this metric, demonstrating greater functional diversity among early catarrhines than previously recognised.

The Influence of Leaping Frequency on Secondary Bone in Cercopithecid Primates.

Bone remodeling is at least partially mediated by the mechanical environment created by an animal's behavior. Here, we test the hypothesis that bone remodeling is primarily induced by high magnitude loads, likely encountered during leaping/bounding behaviors. Osteon population density (OPD), osteon cross-sectional area (On.Ar), and relative osteonal area (%HAV) were measured from femoral and humeral midshaft thin sections of four cercopithecids (N = 5 per species) from Taï Forest, Côte d'Ivoire: Colobus polykomos, Piliocolobus badius, Cercopithecus diana, and Cercocebus atys. All species are generalized quadrupeds but vary in leaping frequency and overall activity budget. Differences between taxa with high (C. polykomos and P. badius) and low leaping frequency (C. diana and C. atys) were assessed via a phylogenetically informed generalized linear mixed model using Markov Chain Monte Carlo methods. Femoral OPD and %HAV are greater in the high frequency leapers than in low frequency leapers, suggesting that frequent high magnitude loads engender remodeling, however, there is no similar pattern in the humerus, which presumably also experiences high magnitude loads during leaping. Additionally, OPD and %HAV are greater in the humerus than the femur, despite load magnitude being presumably higher in the femur. These results provide conflicting support for hypotheses about load magnitude and load frequency as they relate to bone remodeling activity. Future work is proposed to parse out the respective effects of load magnitude and frequency on bone remodeling. Anat Rec, 302:1116-1126, 2019. © 2018 Wiley Periodicals, Inc.

Paternity data and relative testes size as measures of level of sperm competition in the Cercopithecoidea.

Historically, the empirical study of the role of sperm competition in the evolution of sexual traits has been problematic through an enforced reliance on indirect proxy measures. Recently, however, a procedure was developed that uses paternity data to measure sperm competition level directly in terms of males/conception (i.e., the number of males that have sperm present in a female's ampulla at conception). When tested on apes and humans (Hominoidea) this measure proved not only to correlate significantly with the traditionally used measure of relative testes size but also to offer a number of advantages. Here we provide a second test of the procedure, this time using paternity data for the Old World monkeys (Cercopithecoidea). We calculate sperm competition levels (males/conception) for 17 species of wild and free-ranging cercopithecoids and then analyze the data against measures of relative testes size. Calculated sperm competition levels correlate strongly with relative testes size both with and without phylogenetic control at both the species and generic levels. The signal-to-noise ratios inherent in both the past measure of relative testes size and the new measure of sperm competition level from paternity data are discussed. We conclude that although both measures are appropriate for the future study of the role of sperm competition in the evolution of sexual traits, when paternity data are available they provide the more direct and meaningful analytical tool. Not least, they potentially allow a first empirical analysis of the role of sperm competition in the evolution of relative testes size that could then be compared with the wealth of theoretical analyses that already exist.

Associations Between Nutrition, Gut Microbiome, and Health in A Novel Nonhuman Primate Model.

Red-shanked doucs (Pygathrix nemaeus) are endangered, foregut-fermenting colobine primates which are difficult to maintain in captivity. There are critical gaps in our understanding of their natural lifestyle, including dietary habits such as consumption of leaves, unripe fruit, flowers, seeds, and other plant parts. There is also a lack of understanding of enteric adaptations, including their unique microflora. To address these knowledge gaps, we used the douc as a model to study relationships between gastrointestinal microbial community structure and lifestyle. We analyzed published fecal samples as well as detailed dietary history from doucs with four distinct lifestyles (wild, semi-wild, semi-captive, and captive) and determined gastrointestinal bacterial microbiome composition using 16S rRNA sequencing. A clear gradient of microbiome composition was revealed along an axis of natural lifestyle disruption, including significant associations with diet, biodiversity, and microbial function. We also identified potential microbial biomarkers of douc dysbiosis, including Bacteroides and Prevotella, which may be related to health. Our results suggest a gradient-like shift in captivity causes an attendant shift to severe gut dysbiosis, thereby resulting in gastrointestinal issues.

Forelimb morphology and substrate use in extant Cercopithecidae and the fossil primate community of the Hadar sequence, Ethiopia.

It is suggested that joint architecture of the extant cercopithecid forelimb differentiates terrestrial from arboreal quadrupedal species. Linear dimensions of forelimb joint morphology have also been used to assign fossil species to locomotor categories. However, many primates use a mix of terrestrial and arboreal behaviors, which can be problematic when developing models of behavior reconstruction using morphological variation. The current study uses multivariate analyses to identify morphology related to substrate use in primates, including determination of semiterrestriality. Measurements collected from distal humeri and proximal ulnae of 49 extant cercopithecid primate species were selected based on studies indicating that they could individually predict substrate use. Analyses including one-way analysis of variance, principal components, and discriminant functions were conducted to assess their ability to differentiate between arboreal and terrestrial substrate use. The functions created in these analyses are then applied to data from fossil specimens from the Hadar sequence, Ethiopia, sampling both the Hadar and overlying Busidima Formations, to retrodict possible substrate behavior of fossil monkeys at Hadar through time. As this study is designed to identify function and behavior rather than phylogeny, the taxonomic assignment of the fossil specimens is sometimes uncertain, but substrate behavior can still be inferred. Results suggest that substrate use, including semiterrestrial behavior, in extant and extinct primates can be inferred successfully from multivariate analyses based on joint morphology of the monkey elbow. This study reveals that the ecological distribution of primarily terrestrial fossil primate species of the Hadar sequence is comparable to modern-day communities in habitats similar to those reconstructed for the Hadar members.

Evidence for paternal kin bias in the social affiliation of adult female blue monkeys.

If animals increase inclusive fitness by cooperating with relatives, nepotism should involve maternal and paternal kin equally, all else being equal. Evidence of a behavioral bias toward paternal half-siblings in primates is both limited and mixed, with most positive reports from papionins. To expand knowledge of paternal kin recognition, particularly in cercopithecine monkeys, we examined evidence for paternal kin bias in wild blue monkeys (Cercopithecus mitis), a species living mostly in one-male groups. Seasonal breeding and the amount of male reproductive skew in blue monkeys suggests that opportunities to distinguish paternal kin are plentiful, and their social system would make such discrimination beneficial. We compared spatial association and social contact (grooming and contact-sitting) of 20 adult females with at least one paternal half-sibling and at least one non-relative that were present at the same time. We used two data sets, one in which social partners were other parous females, the other in which they were juveniles. Data came from a 7-year period. When interacting with other adult females, subjects groomed and sat in contact with paternal half-siblings significantly more than with known non-kin, and there was a similar trend for spatial association. We detected no paternal kin bias in interactions with juvenile partners. Kin-biased affiliative contact with adult female partners did not appear to be based on age proximity, measured by birth cohort. The study species' social system suggests phenotype matching as the most likely alternative mechanism, though we could not test it directly. Across both behaviors, there was no significant relationship between the number of matrilineal kin a subject had and the degree to which she preferred paternal half-siblings over non-kin as affiliative partners. These findings contribute to a comparative understanding of paternal kin recognition in primates.

Variations in diet composition of sympatric Trachypithecus francoisi and Macaca assamensis in the limestone habitats of Nonggang, China.

Comparative studies of sympatric species are essential for understanding behavioral and ecological adaptation as well as the mechanisms that can reduce resource competition to allow coexistence. François' langurs (Trachypithecus francoisi) and Assamese macaques (Macaca assamensis) are sympatric primate species found in the limestone seasonal rainforests of Nonggang Nature Reserve, southwestern Guangxi, China. To explore their different adaptation strategies, we collected data on diet using scan sampling at 15-min intervals. Our results revealed that François' langurs showed a more flexible diet composition than Assamese macaques. François' langurs increased dietary diversity and mature leaf consumption in response to seasonal scarcity of preferred young leaves and fruits, whereas Assamese macaques relied heavily on young bamboo leaves (Indocalamus calcicolus) in most months. These variations reflect the differences in digestive physiology, morphology, and the temporal and spatial distribution of food resources.

An anatomical and mechanical analysis of the douc monkey (genus Pygathrix), and its role in understanding the evolution of brachiation.

OBJECTIVES: Pygathrix is an understudied Asian colobine unusual among the Old World monkeys for its use of arm-swinging. Little data exists on the anatomy and mechanics of brachiation in this genus. Here, we consider this colobine to gain insight into the parallel evolution of suspensory behavior in primates. MATERIALS AND METHODS: This study compares axial and appendicular morphological variables of Pygathrix with other Asian colobines. Additionally, to assess the functional consequences of Pygathrix limb anatomy, kinematic and kinetic data during arm-swinging are included to compare the douc monkey to other suspensory primates (Ateles and Hylobates). RESULTS: Compared to more pronograde species, Pygathrix and Nasalis share morphology consistent with suspensory locomotion such as its narrower scapulae and elongated clavicles. More distally, Pygathrix displays a gracile humerus, radius, and ulna, and shorter olecranon process. During suspensory locomotion, Pygathrix, Ateles, and Hylobates all display mechanical convergence in limb loading and movements of the shoulder and elbow, but Pygathrix uses pronated wrist postures that include substantial radial deviation during arm-swinging. DISCUSSION: The adoption of arm-swinging represents a major shift within at least three anthropoid clades and little data exist about its transition. Across species, few mechanical differences are observed during arm-swinging. Apparently, there are limited functional solutions to the challenges associated with moving bimanually below branches, especially in more proximal forelimb regions. Morphological data support this idea that the Pygathrix distal forelimb differs from apes more than its proximal end. These results can inform other studies of ape evolution, the pronograde to orthograde transition, and the convergent ways in which suspensory locomotion evolved in primates.

Non-invasive assessment of adrenocortical function as a measure of stress in the endangered golden langur.

The golden langur (Trachypithecus geei) is an endangered primate endemic to northern India and Bhutan. The main stressors to the species are habitat degradation and fragmentation. Non-invasive fecal glucocorticoid metabolite (fGCM) analysis is a powerful tool for assessing stress associated with environmental disturbances in wildlife. However, interspecific differences in glucocorticoid metabolism require careful selection of the antibody used in their quantification. The goals of this study were to: 1) validate an enzyme immunoassay (EIA) to determine fecal GC metabolite (fGCM) concentrations in the golden langur and 2) compare fGCM concentrations between golden langurs living under different environmental conditions. We compared five enzyme immunoassays for determining stress related physiological responses in golden langurs by performing an adrenocorticotropic stimulation test in both sexes. Our validations identified an 11-oxoaetiocholanolone EIA detecting 11, 17 dioxoandrostanes as the most suitable assay for monitoring adrenocortical activity in the species. FGCM concentrations from semi-captive temple langurs were significantly higher than respective stress steroid concentrations in free-ranging or pet/zoo langurs. This study presents a validated practical method for non-invasive monitoring of adrenocortical function in this rare and declining species.

A new record of the capped langur (Trachypithecus pileatus) in China.

The distribution of the capped langur (Trachypithecus pileatus) in China has become controversial since Shortridge's langur (Trachypithecus shortridgei) was upgraded to a full species. The capped langur is considered to be distributed in northeast India, Bangladesh, Bhutan, and northwest Myanmar only (Brandon-Jones et al., 2004; Choudhury, 2008, 2014; Das et al., 2008; Groves, 2001). In our field survey, however, we obtained photos of the capped langur, demonstrating its existence in China.

Group Composition and Monandry in Grizzled Langurs, Presbytis comata, on Java.

Grizzled langurs, Presbytis comata, a largely sexually monomorphic species, are reported to occur in populations where either the majority of groups comprise 1 adult male with 1 adult female, or where groups comprise 1 adult male with multiple females. As such, they may have a monandrous mating system. I investigated whether 1-male/1-female groups indeed form a significant part of the species' social system, and whether habitat variation (forest fragment size, distance to the forest edge, altitude) affects social organization. I found the species from sea level to 2,565 m above sea level in groups from 1 to 13 individuals. I recorded mostly 1-male/multifemale groups with offspring or, alternatively, all-male groups. Two out of 55 groups comprised 1-male/1-female groups with offspring. Group size was negatively correlated with altitude and forest fragment size, and positively correlated with increasing distance from the forest edge. Altitudinal variation in group sizes was driven mainly by fewer adult females being present in groups at higher elevations; the number of adult males (almost invariably 1), subadults, juveniles, and infants, as well as the infant/adult female ratio, showed little altitudinal variation. One-male/1-female groups have been recorded repeatedly over a 25-year period in a high-altitude population on Mt. Patuha, West Java, but even here, on average, three fifths of the groups comprise 1 adult male with multiple females. At high-altitude sites, P. comata may indeed have a monandrous mating system, but at lower elevations it seems similar to that of other Presbytis langurs.

Dietary diversity, feeding selectivity, and responses to fruit scarcity of two sympatric Bornean primates (Hylobates albibarbis and Presbytis rubicunda rubida).

Effectively characterizing primate diets is fundamental to understanding primate behavior, ecology and morphology. Examining temporal variation in a species' diet, as well as comparing the responses of different species to variation in resource availability, can enhance understanding of the evolution of morphology and socioecology. In this study, we use feeding data collected over five years to describe the diets of two sympatric Southeast Asian primate species of similar body size: white-bearded gibbons (Hylobates albibarbis) and red leaf monkeys (Presbytis rubicunda rubida), in Gunung Palung National Park, West Kalimantan, Indonesia. Long-term data sets are especially important for characterizing primate diets in Southeast Asia, where the forests exhibit supra-annual mast fruiting events. We found that gibbons were mainly frugivorous, with fruit and figs comprising 70% of their 145 independent feeding observations, whereas leaf monkeys ate a substantial amount of seeds (26%), fruits and figs (26.5%) and leaves (30%, n = 219 independent feeding observations). Leaf monkeys consumed a higher number of plant genera, and this was due mostly to the non-frugivorous portion of their diet. To investigate resource selection by these primates we utilized two different approaches: the Manly Selectivity Ratio, which did not take into account temporal variation of resource availability, and a model selection framework which did incorporate temporal variation. Both species selected figs (Ficus) more than predicted based on their availability under the Manly Selectivity Ratio. Model selection allowed us to determine how these primates alter the proportion of leaves, flowers, seeds, figs and fruit in their diets in response to variation in fruit availability. When fruits were scarce, both gibbons and leaf monkeys incorporated more leaves and figs into their diets, indicating that these two food classes are fallback foods for these primates. We discuss how different measures of resource selection can provide seemingly contradictory results, and emphasize the importance of long term studies that combine independent feeding observations with rigorous assessment of temporal variation in resource availability when modelling feeding selectivity.

Effect of habitat fragmentation on ranging behavior of white-headed langurs in limestone forests in Southwest China.

The critically endangered white-headed langur (Trachypithecus leucocephalus) is confined to fragmented karst forests of southwest Guangxi Province, China. A lack of information on the influence of habitat fragmentation on langur behavior has prevented a comprehensive understanding of their ranging behavior and the development of effective langur conservation strategies. We collected comparative data on time budgets, daily path lengths, home range and diets of four langur groups inhabiting the lightly fragmented Fusui forest (G1, G2) and the more heavily fragmented Chongzuo forest (G3, G4). The aim was to explore the effect of this fragmentation on langur ranging behavior. Our results showed that the Fusui groups spent more time on moving and less time on feeding and playing than the Chongzuo groups. Daily path lengths were 472.4-536.1 m for the Fusui groups and 449.6-480.7 m for the Chongzuo groups, indicating no marked inter-site variation. The Fusui groups occupied much larger home ranges (23.8-33.8 ha) than the Chongzuo groups (14.5-15.8 ha). However, all groups had similar monthly home ranges. Diets significantly differed among langur groups. The Fusui groups consumed more young leaves and had much lower diet diversity compared with the Chongzuo groups. Our findings indicate that habitat fragmentation is one of the crucial determinants of white-headed langur ranging behavior because fragmentation reduces and restricts the home range. Langurs in fragmented habitat adopt an energy conservation strategy characterized by devoting more time to feeding and less time to moving, with a smaller home range and consumption of more plant species. We argue that linking fragmented forests with corridors should be considered a priority in a wider and comprehensive longer term langur population conservation and habitat management strategy.

Humeral correlates of forelimb elevation in four West African cercopithecid monkeys.

OBJECTIVES: We previously found that differing degrees of forelimb flexion, elevation, and abduction during nonlocomotor foraging activities covaried with scapular morphology among four sympatric cercopithecids. The purpose of this study is to investigate whether features of the proximal humerus are similarly related to forelimb elevation during foraging. METHODS: Our sample consists of humeri (n = 42) of adult Cercocebus atys, Cercopithecus diana, Colobus polykomos, and Piliocolobus badius collected from Côte d'Ivoire's Taï National Park. Features of the proximal humerus known to correspond with varying degrees of forelimb mobility were examined using a combination of 2-dimensional caliper-based indices and 3-dimensional analyses. RESULTS: Some features of the proximal humerus are consistent with the varying frequencies of forelimb elevation during foraging. For instance, the red colobus (P. badius) has a variety of features consistent with more pronounced shoulder mobility and forelimb flexibility including a wider, more distally projecting deltoid plane, greater tuberosity positioned below the humeral head articular surface, and larger intertuberosity angle. CONCLUSIONS: The colobines, particularly P. badius, display a number of humeral and scapular features indicative of greater arm flexion, elevation, and abduction compared to the two cercopithecines. We conclude that idiosyncrasies in forelimb use during foraging are reflected in functionally relevant features of the cercopithecid proximal humerus, highlighting that postural behavior, in additional to locomotor behavior, can exert selective pressures on primate skeletal form. This result should provide for more informed reconstructions of the full positional repertoires in fossil taxa.