Eastern Lowland Gorillas Research Articles

Applying best practice to feasibility assessment and strategic planning for great ape translocation: A case study of Grauer's gorilla (Gorilla beringei graueri)

We outline the feasibility and risk assessments that are essential prerequisites to conservation translocation of great apes, while upholding the precautionary principle to avoid harms to conspecifics, sympatric taxa and ecosystems. As part of a strategic planning process, we addressed key questions on the costs and benefits of a translocation of Grauer's gorillas in Democratic Republic of Congo. We reviewed published and gray literature to compile data on Grauer's gorilla ecology and potential release sites in the subspecies' geographic range. Taking into account ecological dimensions of the habitats, impacts on conspecifics, sympatric great apes and other wildlife, and existing threats, we formulated recommendations on whether and where translocation could benefit conservation of this taxon. We concluded that one site assessed is compatible with key IUCN criteria. At Mt. Tshiaberimu in Virunga National Park, the resident Grauer's gorilla population is non-viable, no sympatric great ape species is present and the site is actively protected against poaching and habitat encroachment. Conservation translocations are widely used for species recovery; however, detailed accounts of the analyses and planning required to adhere to IUCN best practice are rare. Our approach enabled evidence-based determination of feasibility despite some initial information gaps. The process is widely applicable and could encourage improved compliance with IUCN guidelines when risks to wild conspecifics might be high, yet ecological knowledge of the target population is limited. The Grauer's Gorilla Conservation and Reinforcement Project is a partnership between the Gorilla Rehabilitation and Conservation Education Center, Virunga National Park and Re:wild.

Evaluating the muscle attachment hypothesis for sagittal cresting in Gorilla and Pongo.

Primate mandibular morphology is often associated with jaw functionality of the masticatory complex in the context of variation in diets. Recent research into the disparities between the diet and jaw functionality in male and female hominoids is inconclusive and suggests that sexual dimorphism in the mandible may be influenced by external factors such as temporalis and masseter muscle morphology, which in turn may be influenced by sexual selection. As the muscles associated with mastication (i.e., the type of chewing exhibited by primates and other mammals) encompass the mandible as well as the neurocranium, including the sagittal crest among some individuals, this study investigates sex-specific associations between regions of the mandibular ramus and neurocranium associated with mastication in a dentally mature sample of Gorilla and Pongo. A total of four cranial and mandibular variables were measured in two Gorilla taxa (Gorilla gorilla gorilla and Gorilla beringei graueri) and one Pongo taxon (Pongo pygmaeus pygmaeus) (n = 220). For all three taxa, we investigate (a) whether the degree of sexual dimorphism in cranial regions associated with sagittal cresting (sagittal crest size (SCS) and temporalis muscle attachment area (TMAA)) is proportional to the degree of mandibular ramus area (MRA) and coronoid process height (CPH) sexual dimorphism, (b) whether there are sex differences in scaling relationships between TMAA and MRA, and (c) whether there are sex differences in the strength of association between TMAA and CPH. We show that for G. g. gorilla, variables associated with sagittal cresting show higher sexual dimorphism values than our two mandibular ramus variables, which is not the case for G. b. graueri or for P. p. pygmaeus. All three taxa show similar sex-specific scaling relationships between TMAA and MRA, where for males this relationship does not diverge from isometry, and for females there is a negative allometric relationship. Our findings also show intraspecific sex differences in allometric slopes between MRA and TMAA for all three taxa. Only G. g. gorilla shows a significant association between TMAA and CPH, which is observed in both sexes. Although there are some statistical associations between the cranial and mandibular regions associated with mastication, our results show that among male gorillas and orangutans, patterns of variation in the sagittal crest, TMAA, mandibular ramus and the coronoid process cannot be explained by the muscle attachment hypothesis alone. These findings have implications surrounding the associations between social behaviour and the morphology of the craniofacial complex.

Group structure and individual relationships of sanctuary-living Grauer's gorillas (Gorilla beringei graueri).

The study of individual social relationships and group structure provides insights into a species' natural history and can inform management decisions for animals living in human care. The Gorilla Rehabilitation and Conservation Education (GRACE) center provides permanent sanctuary for a group of 14 Grauer's gorillas (Gorilla beringei graueri), a critically endangered and poorly studied subspecies of the genus gorilla, in the Democratic Republic of the Congo. We monitored the association patterns of the gorillas at GRACE over eight months and here describe their individual relationships and group structure via multiple social network statistics. The group was highly connected but associations between individuals were weak on average. Social network metrics describe that an adult female was the most gregarious and socially central individual within the group. In fact, adult females were the most gregarious and socially central on average. Group level association patterns were significantly correlated over the study period and across observation types, suggesting the group was socially stable during the eight month study period. The data collected in this study were done so by GRACE caregivers as part of their daily husbandry routine and provided important insights into this group's behavior, ultimately informing on their care, welfare and future release considerations. The methodological approaches implemented here are easily scalable to any primate sanctuary or care facility seeking to use data to inform husbandry and management procedures. Lastly, our study is the first social network analysis to be conducted on Grauer's gorillas and provides tentative insights into the behavior of this poorly studied subspecies. Though more research is needed to evaluate if the findings here are reflective of this subspecies' natural history or the idiosyncrasies of the group.

Sexual dimorphism in the cranium and endocast of the eastern lowland gorillas (Gorilla beringei graueri)

Sexual dimorphism of the nervous system has been reported for a wide range of vertebrates. However, understanding of sexual dimorphism in primate cranial structures and soft tissues, and more particularly the brain, remains limited. In this study, we aimed to investigate the external and internal (i.e., endocast) cranial differences between male and female eastern lowland gorillas (Gorilla beringei graueri). We examined the differences in the size, shape, and disparity with the aim to compare how sexual dimorphism can impact these two structures distinctively, with a particular focus on the endocranium. To do so, we reconstructed gorilla external crania and endocasts from CT scans and used 3D geometric morphometric techniques combined with multivariate analyses to assess the cranial and endocranial differences between the sexes. Our results highlighted sexual dimorphism for the external cranium and endocast with regard to both size and shape. In particular, males display an elongated face accompanied by a pronounced sagittal crest and an elongated endocast along the rostroposterior axis, in contrast to females who are identified by a more rounded brain case and endocast. Males also show a significantly larger external cranium and endocast size than females. In addition, we described important differences for the posterior cranial fossae (i.e., the position of the cerebellum within the brain case) and olfactory bulb between the two sexes. Particularly, our results highlighted that, relatively to males, females have larger posterior cranial fossae, whereas males have been characterized by a larger and rostrally oriented olfactory bulb.

Ghost admixture in eastern gorillas

Archaic admixture has had a substantial impact on human evolution with multiple events across different clades, including from extinct hominins such as Neanderthals and Denisovans into modern humans. In great apes, archaic admixture has been identified in chimpanzees and bonobos but the possibility of such events has not been explored in other species. Here, we address this question using high-coverage whole-genome sequences from all four extant gorilla subspecies, including six newly sequenced eastern gorillas from previously unsampled geographic regions. Using approximate Bayesian computation with neural networks to model the demographic history of gorillas, we find a signature of admixture from an archaic ‘ghost’ lineage into the common ancestor of eastern gorillas but not western gorillas. We infer that up to 3% of the genome of these individuals is introgressed from an archaic lineage that diverged more than 3 million years ago from the common ancestor of all extant gorillas. This introgression event took place before the split of mountain and eastern lowland gorillas, probably more than 40 thousand years ago and may have influenced perception of bitter taste in eastern gorillas. When comparing the introgression landscapes of gorillas, humans and bonobos, we find a consistent depletion of introgressed fragments on the X chromosome across these species. However, depletion in protein-coding content is not detectable in eastern gorillas, possibly as a consequence of stronger genetic drift in this species.

Viability analysis for population reinforcement of Grauer's gorillas at Mount Tshiaberimu, Democratic Republic of the Congo

AbstractReintroduction and translocation programs have been sparingly used for the management of endangered primate populations. Mount Tshiaberimu in eastern Democratic Republic of the Congo (DRC) contains 6 Grauer's gorillas (Gorilla beringei graueri) with only 2 adult females. Without intervention, this population is at high risk of extinction. We designed population viability analysis models to compare different release scenarios of wild‐born captive female gorillas housed at the Gorilla Rehabilitation and Conservation Education (GRACE) Center in the DRC. We identified the minimum number of females needed to maintain a viable population in this habitat. We used a stochastic Leslie matrix model and a more complex individual‐based model to project population growth. We used published demographic parameters for mountain gorillas (Gorilla b. beringei) corresponding to a 3.2% annual growth rate, and then applied a correction factor to female fertility to obtain parameters consistent with 1% and 2% growth rates. We ran each scenario over a 50‐year time period (1,000 simulations) to determine the final population size and risk of local extinction. Results from our optimistic (3.2% growth) and conservative (1% growth) individual‐based model projections indicated that the extinction risk dropped below 1% with the release of at least 2 or 3 females, respectively. Both approaches predicted similar extinction risks for all scenarios; however, the variance in final population size was higher with the individual‐based model. For long‐lived mammals like primates, we recommend the use of individual‐based models, which can incorporate life‐history parameters such as long gestation and nursing periods. Our analysis suggests a translocation of ≥3 females to rescue the Tshiaberimu gorilla population in the short term. Factors such as inbreeding depression, habitat quality, disease risks, and anthropogenic pressures will need to be evaluated in later stages of population reinforcement planning.

Ecology, Not Host Phylogeny, Shapes the Oral Microbiome in Closely Related Species.

Host-associated microbiomes are essential for a multitude of biological processes. Placed at the contact zone between external and internal environments, the little-studied oral microbiome has important roles in host physiology and health. Here, we investigate the roles of host evolutionary relationships and ecology in shaping the oral microbiome in three closely related gorilla subspecies (mountain, Grauer's, and western lowland gorillas) using shotgun metagenomics of 46 museum-preserved dental calculus samples. We find that the oral microbiomes of mountain gorillas are functionally and taxonomically distinct from the other two subspecies, despite close evolutionary relationships and geographic proximity with Grauer's gorillas. Grauer's gorillas show intermediate bacterial taxonomic and functional, and dietary profiles. Altitudinal differences in gorilla subspecies ranges appear to explain these patterns, suggesting a close connection between dental calculus microbiomes and the environment, likely mediated through diet. This is further supported by the presence of gorilla subspecies-specific phyllosphere/rhizosphere taxa in the oral microbiome. Mountain gorillas show a high abundance of nitrate-reducing oral taxa, which may promote adaptation to a high-altitude lifestyle by modulating blood pressure. Our results suggest that ecology, rather than evolutionary relationships and geographic distribution, shape the oral microbiome in these closely related species.

Ecological divergence and calcaneal‐cuboid morphology in gorillas

AbstractObjectivesGorillas are diverse behaviorally and ecologically with higher frequencies of arboreality and frugivory observed in populations living at lower altitudes compared to those living at higher altitudes. Previous studies have shown that the more arboreal western lowland gorilla has hallucial tarsometatarsal and talocrural joint morphologies associated with enhanced hallucial abduction and foot inversion capabilities whereas the more terrestrial eastern gorilla does not. Here we examine how known ecological and behavioral differences among gorillas relate to variation in calcaneal and cuboid morphology. Specifically, we test whether gorillas that climb more frequently (i.e., western lowland and lowland grauer gorillas) have cuboid‐metatarsal and calcaneocuboid morphologies that facilitate increased foot mobility compared to those that climb less often (i.e., mountain and highland grauer gorillas).MethodsWe quantify the relative areas of articular and nonarticular surfaces, angles between articular surfaces, articular surface curvatures, the relative length and depth of the calcaneocuboid joint, and the relative size of the calcaneal tuber using three‐dimensional models of gorilla calcanei and cuboids (n = 90 and 81, respectively).ResultsOur results, based on univariate and multivariate analyses, show that western and eastern gorillas follow our predicted arboreal‐terrestrial morphocline in terms of their calcaneal and cuboid morphology; however, highland and lowland grauer gorilla populations do not.ConclusionsThis study has implications for understanding gorilla foot function and the evolutionary processes responsible for producing the morphological patterns among living gorilla populations. Future studies of gorilla morphological diversity may provide a useful comparative model for studies of locomotor evolution in extinct clades.

Simian homologues of human herpesviruses and implications for novel viral introduction to free-living mountain gorillas.

The endangered mountain gorilla (Gorilla beringei beringei) in Rwanda, Uganda, and the Democratic Republic of Congo is frequently in contact with humans through tourism, research activities, and illegal entry of people into protected gorilla habitat. Herpesviruses, which are ubiquitous in primates, have the potential to be shared in any setting where humans and gorillas share habitat. Based on serological findings and clinical observations of orofacial ulcerated lesions resembling herpetic lesions, an alpha-herpesvirus resembling human herpes simplex virus type 1 (HSV-1) has long been suspected to be present in human-habituated mountain gorillas in the wild. While the etiology of orofacial lesions in the wild has not been confirmed, HSV-1 has been suspected in captively-housed mountain gorillas and confirmed in a co-housed confiscated Grauer's gorilla (Gorilla beringei graueri). To better characterize herpesviruses infecting mountain gorillas and to determine the presence/absence of HSV-1 in the free-living population, we conducted a population-wide survey to test for the presence of orally shed herpesviruses. DNA was extracted from discarded chewed plants collected from 294 individuals from 26 groups, and samples were screened by polymerase chain reaction using pan-herpesvirus and HSV-1-specific assays. We found no evidence that human herpesviruses had infected free-ranging mountain gorillas. However, we found gorilla-specific homologs to human herpesviruses, including cytomegaloviruses (GbbCMV-1 and 2), a lymphocryptovirus (GbbLCV-1), and a new rhadinovirus (GbbRHV-1) with similar characteristics (i.e., timing of primary infection, shedding in multiple age groups, and potential modes of transmission) to their human counterparts, human cytomegalovirus, Epstein-Barr virus and Kaposi's sarcoma-associated herpesvirus, respectively.

Isolated Grauer's gorilla populations differ in diet and gut microbiome.

The animal gut microbiome has been implicated in a number of key biological processes, ranging from digestion to behaviour, and has also been suggested to facilitate local adaptation. Yet studies in wild animals rarely compare multiple populations that differ ecologically, which is the level at which local adaptation may occur. Further, few studies simultaneously characterize diet and gut microbiome from the same sample, despite their probable interdependence. Here, we investigate the interplay between diet and gut microbiome in three geographically isolated populations of the critically endangered Grauer's gorilla (Gorilla beringei graueri), which we show to be genetically differentiated. We find population- and social group-specific dietary and gut microbial profiles and covariation between diet and gut microbiome, despite the presence of core microbial taxa. There was no detectable effect of age, and only marginal effects of sex and genetic relatedness on the microbiome. Diet differed considerably across populations, with the high-altitude population consuming a lower diversity of plants compared to low-altitude populations, consistent with plant availability constraining dietary choices. The observed pattern of covariation between diet and gut microbiome is probably a result of long-term social and environmental factors. Our study suggests that the gut microbiome is sufficiently plastic to support flexible food selection and hence contribute to local adaptation.

Facial asymmetry tracks genetic diversity among Gorilla subspecies.

Mountain gorillas are particularly inbred compared to other gorillas and even the most inbred human populations. As mountain gorilla skeletal material accumulated during the 1970s, researchers noted their pronounced facial asymmetry and hypothesized that it reflects a population-wide chewing side preference. However, asymmetry has also been linked to environmental and genetic stress in experimental models. Here, we examine facial asymmetry in 114 crania from three Gorilla subspecies using 3D geometric morphometrics. We measure fluctuating asymmetry (FA), defined as random deviations from perfect symmetry, and population-specific patterns of directional asymmetry (DA). Mountain gorillas, with a current population size of about 1000 individuals, have the highest degree of facial FA (explaining 17% of total facial shape variation), followed by Grauer gorillas (9%) and western lowland gorillas (6%), despite the latter experiencing the greatest ecological and dietary variability. DA, while significant in all three taxa, explains relatively less shape variation than FA does. Facial asymmetry correlates neither with tooth wear asymmetry nor increases with age in a mountain gorilla subsample, undermining the hypothesis that facial asymmetry is driven by chewing side preference. An examination of temporal trends shows that stress-induced developmental instability has increased over the last 100 years in these endangered apes.

Diversity and diel activity patterns of terrestrial mammals in the Nkuba Conservation Area, Democratic Republic of the Congo

AbstractThe Congo basin forests have vast conservation potential but because of their inaccessibility and periodic insecurity there is little formal protection or ecological research occurring there. Community-based conservation efforts in the unprotected forest corridor separating Kahuzi-Biega and Maiko National Parks in eastern Democratic Republic of the Congo aim to protect a unique forest ecosystem and facilitate the development of ecological research. To support this process, we obtained baseline data on the occurrence of terrestrial mammals in the Nkuba Conservation Area by conducting camera-trap (2014–2018) and transect (2013–2018) surveys. From camera-trap images we also extracted diel activity patterns and estimated overlap in these patterns between selected pairs of species. We identified 29 mammal species weighing > 1 kg using camera traps and 22 species in transect surveys, with a total of 33 mammal species, of which seven are categorized as threatened on the IUCN Red List. Among this mammalian community, we recorded nocturnal and diurnal species with short core activity periods, and several cathemeral species with long activity periods, with various degrees of temporal separation of diel activity between species. The presence of threatened species, including the Critically Endangered Grauer's gorilla Gorilla beringei graueri, suggests that the Nkuba Conservation Area harbours a forest community that requires continuous monitoring, further research and investment in protection from the ongoing deforestation and resource exploitation occurring in the surrounding region.

The complex Y-chromosomal history of gorillas.

Studies of the evolutionary relationships among gorilla populations using autosomal and mitochondrial sequences suggest that male-mediated gene flow may have been important in the past, but data on the Y-chromosomal relationships among the gorilla subspecies are limited. Here, we genotyped blood and noninvasively collected fecal samples from 12 captives and 257 wild male gorillas of known origin representing all four subspecies (Gorilla gorilla gorilla, G. g. diehli, G. beringei beringei, and G. b. graueri) at 10 Y-linked microsatellite loci resulting in 102 unique Y-haplotypes for 224 individuals. We found that western lowland gorilla (G. g. gorilla) haplotypes were consistently more diverse than any other subspecies for all measures of diversity and comprised several genetically distinct groups. However, these did not correspond to geographical proximity and some closely related haplotypes were found several hundred kilometers apart. Similarly, our broad sampling of eastern gorillas revealed that mountain (G. b. beringei) and Grauer's (G. b. graueri) gorilla Y-chromosomal haplotypes did not form distinct clusters. These observations suggest structure in the ancestral population with subsequent mixing of differentiated haplotypes by male dispersal for western lowland gorillas, and postisolation migration or incomplete lineage sorting due to short divergence times for eastern gorillas.

Changes in Grauer's gorilla ( Gorilla beringei graueri ) and other primate populations in the Kahuzi‐Biega National Park and Oku Community Reserve, the heart of Grauer's gorilla global range

Changes in Grauer's gorilla ( Gorilla beringei graueri ) and other primate populations in the Kahuzi‐Biega National Park and Oku Community Reserve, the heart of Grauer's gorilla global range

Changes in Grauer's gorilla (Gorilla beringei graueri) and other primate populations in the Kahuzi-Biega National Park and Oku Community Reserve, the heart of Grauer's gorilla global range.

Grauer's gorillas (Gorilla beringei graueri) have declined drastically across their range in eastern Democratic Republic of Congo (DRC). Survey data analysed in 2016 estimated a 77% decline in numbers between the mid- 1990s and 2016 and predicted that Kahuzi-Biega National Park (KBNP), and the contiguous Oku Community Reserve (OCR) held much of the global population. An estimate of 3800 Grauer's gorillas was made across its range at that time. Here, we publish the most extensive survey of Grauer's gorilla numbers to date, using nest counts from 230 line transects across KBNP and OCR to derive more accurate estimates of both gorilla and chimpanzee numbers. Gorilla numbers were estimated from line transects at 1,571 (95% confidence interval [CI]: 824-2,993) within KBNP and at 2,244 (95% CI: 1,471-3,422) in OCR. Eastern chimpanzee (Pan troglodytes schweinfurthii) numbers were estimated at 2,500 (95% CI: 1,804-3,462) in KBNP and 687 (95% CI: 472-999) in OCR. Estimates of total numbers for the survey area were 5,252 (95% CI: 3,687-7,481) Grauer's gorillas and 4,275 (95% CI: 3,322-5,502) eastern chimpanzees. Chimpanzee numbers were not significantly different from the estimates in the mid-1990s but the gorillas had significantly declined, mostly in KBNP. Modeled densities of these apes indicated that distances to mines, villages, or roads significantly explained part of the distribution of these apes, with higher densities also found in more rugged and remote sites. Other primates have all declined in this region, likely due to bushmeat hunting, especially the Endangered Ulindi River Red Colobus Piliocolobus lulindicus. These results confirm the negative impact of insecurity on Grauer's gorilla but indicate that the population declines may not be as great as previously feared. Using our revised gorilla density estimate we revise the original estimate of global numbers from 3,800 to 6,800 individuals.

A case study of improved cook stoves in primate conservation from Democratic Republic of Congo.

Human communities living near nonhuman primate habitats often depend on wood from forests for their energy needs. Improving the efficiency of local cook stoves is a potential "win-win" solution that is commonly promoted to protect forests and improve human health and development. Despite the popularity of improved stove projects in primate conservation, few outcomes have been formally published. As a result, it is currently unclear whether this approach is a wise investment of limited conservation funds. This paper describes a pilot study conducted by the Gorilla Rehabilitation and Conservation Education Center to evaluate the potential for using improved stoves for the conservation of an important habitat for Grauer's gorillas and chimpanzees in eastern Democratic Republic of Congo. Community surveys and observations of human forest use revealed a heavy local reliance on forest-derived wood. Wood was the main source of fuel used in households, the most highly valued forest resource, and the primary resource extracted during forest observations. It was primarily collected by women and children. The use of traditional, inefficient three-stone hearths for cooking was also widespread. A 2-year campaign using a community-based social marketing approach resulted in an increase in improved stove installations from 18% to 78% of households in one village. After stove adoption, weekly household wood consumption was reduced by half. Campaign elements that showed promise include promotion using women's networks and intensive follow-up assessment and support. We conclude that, if scaled up, improved stoves may be a useful strategy for reducing encroachment into our target protected area but that successful implementation will require a significant long-term commitment with evaluation and oversight. It is recommended that before investing in improved stoves, primate conservation projects take long-term and evaluation requirements into consideration.

DIFFUSE IDIOPATHIC SKELETAL HYPEROSTOSIS IN CAPTIVE GORILLAS (GORILLA SPP.): APPEARANCES AND DIAGNOSIS.

Diffuse idiopathic skeletal hyperostosis (DISH) is a disorder of unknown cause, in which new bone forms in soft tissues attached to the skeleton. Originally described in humans, in whom it is quite common, it is usually asymptomatic. New bone may completely bridge across joints, especially in the spine. However, it can be difficult to distinguish from diseases such as spondyloarthritis and spondylosis. With safer and increased use of radiography in diagnosis, the unfamiliar skeletal changes of asymptomatic DISH may now be coincidentally revealed during investigation of other disorders and result in misdiagnosis and unnecessary treatment. There have been case reports of its occurrence in great apes, but this is the first study to illustrate its appearances in a series of 11 skeletons of western and eastern lowland gorillas (Gorilla gorilla gorilla and Gorilla beringei graueri) from zoos in Europe and the United States. The study combines a review of available clinical and postmortem records with examination of the skeletons and radiologic investigation, such as computed tomography (CT). The results indicate that the disorder is probably common in older (>30 yr) captive gorillas, but that it is asymptomatic. It was not symptomatic during life in any of these animals. Several cases had unexpected features, such as extensive involvement of the thorax and extra-articular sacroiliac and tibiofibular joint fusions that are not typical in humans. By illustrating these skeletons, the study should aid differentiation of DISH from spondylosis (syn spondylosis deformans) and spondyloarhritis. It illustrates those features that are atypical of human DISH. CT scanning is valuable in such cases for examining diagnostically important areas such as sacroiliac joints. Increased awareness of DISH should help with understanding its cause, both in gorillas and humans.

Mandibular corpus shape is a taxonomic indicator in extant hominids

The aim of this study is to understand whether the shape of three sub-regions of the mandibular corpus (the alveolar arch, corpus at M1 and posterior symphysis) are useful for making taxonomic assessments at the genus and species levels in extant hominids. We use data taken from 3D surface scans of the mandibular corpus of seven extant hominid taxa: Gorilla gorilla gorilla, Gorilla beringei graueri, Homo sapiens, Pan paniscus, Pan troglodytes schweinfurthii, Pongo abelii, and Pongo pygmaeus pygmaeus to generate four shape variables: alveolar arch shape (AAS), corpus shape at M1 (CSM1 ), posterior symphysis shape at the midline (PSSM), and posterior symphysis shape (PSS). To ascertain how reliable each mandibular shape variable is for assessing taxonomy, we ran canonical discriminant and discriminant function analysis, reporting cross-validated results. Using a combination of three mandibular corpus shape variables, 99% of specimens were classified correctly for genus-level analyses. A maximum of 100% of Pan specimens, 94% of Gorilla specimens and 96% of Pongo specimens were classified correctly at the species level when up to three mandibular shape variables were included in the analyses. When mandibular corpus variables were considered in isolation, posterior symphysis shape yielded the highest overall correct classification results. The high taxonomic classification rates at both the genus and species level, using 3D surface data and advanced quantification techniques, show that the shape of the alveolar arch, corpus at M1 and symphysis can distinguish extant hominid taxa. These findings have implications for assessing the taxonomy of extinct hominid specimens which preserve these mandibular sub-regions.

The Protection of the Gorilla (Gorilla Beringei Graueri) From Itombwe in the Democratic Republic of the Congo (DRC): A Case for Reconciling Environmental and Property Rights

The Protection of the Gorilla (Gorilla Beringei Graueri) From Itombwe in the Democratic Republic of the Congo (DRC): A Case for Reconciling Environmental and Property Rights

Pelvic shape variation among gorilla subspecies: Phylogenetic and ecological signals

Gorillas occupy habitats that range in elevation from 0 to 3850 m. Populations at higher elevations tend to be less arboreal than lowland populations. Variation in habitat-specific behaviors among closely related populations makes gorillas a unique model to study the relationship between locomotion and morphology. The pelvis reflects differences in locomotion in other primates, and thus may also reflect locomotor differences among gorillas. We tested the hypothesis that pelvic morphology exhibits clinal variation across elevation within Gorilla. Using 3D geometric morphometrics and principal components analysis (PCA), we characterized pelvic shape in three gorilla subspecies representing 14 localities across gorillas' full elevation range: western lowland gorillas (Gorilla gorilla gorilla), mountain gorillas (Gorilla beringei beringei), and Grauer's gorillas (Gorilla beringei graueri). We found that the first principal component (PC1) usually reflects differences between western and eastern gorillas in the lateral margin of the ilium and, in males, the obturator foramen. When sexes are considered together, the second principal component (PC2) indicates some separation between G. b. beringei and G. b. graueri, albeit with considerable overlap, corresponding to the shape of the iliac crest. When sexes were analyzed separately, there was no distinction. Phylogenetic generalized least squares regression was used to evaluate the relationship between elevation and pelvic shape under varying phylogenetic assumptions. Models were compared to assess how phylogenetic adjustment affects model fit. Neither of the first two PCs nor overall shape yielded a significant relationship with elevation in any of the pooled-sex and individual-sex samples. This suggests that covariation between pelvic morphology and elevation is sex-specific and dependent on phylogenetic assumptions. Our results find complex interactions between sex, phylogeny, elevation, and pelvic morphology, suggesting that there is not one ecomorphological pattern that characterizes all gorillas.