Mountain Gorillas Research Articles

Correction: Mountain gorillas maintain strong affiliative biases for maternal siblings despite high male reproductive skew and extensive exposure to paternal kin

Correction: Mountain gorillas maintain strong affiliative biases for maternal siblings despite high male reproductive skew and extensive exposure to paternal kin

Cumulative early-life adversity does not predict reduced adult longevity in wild gorillas

Extensive research across fields has repeatedly confirmed that early-life adversity (ELA) is a major selective force for many taxa, in part via its ties to adult health and longevity.1,2,3 Negative effects of ELA on adult outcomes have been documented in a wide range of species, from fish to birds to humans.4 We used 55 years of long-term data collected on 253 wild mountain gorillas to examine the effects of six putative sources of ELA on survival, both individually and cumulatively. Although cumulative ELA was associated with high mortality in early life, we found no evidence that it had detrimental consequences for survival later in life. Experiencing three or more forms of ELA was associated with greater longevity, with a 70% reduction in the risk of death across adulthood, driven specifically by greater longevity in males. Although this higher survival in later life is likely a consequence of sex-specific viability selection5 during early life due to the immediate mortality consequences of adverse experiences, patterns in our data also suggest that gorillas have significant resilience to ELA. Our findings demonstrate that the detrimental consequences of ELA on later life survival are not universal, and indeed largely absent in one of humans' closest living relatives. This raises important questions about the biological roots of sensitivity to early experiences and the protective mechanisms that contribute to resiliency in gorillas, which could be critical for understanding how best to encourage similar resiliency to early-life shocks in humans.

Projecting the impact of an ebola virus outbreak on endangered mountain gorillas

Ebola virus is highly lethal for great apes. Estimated mortality rates up to 98% have reduced the global gorilla population by approximately one-third. As mountain gorillas (Gorilla beringei beringei) are endangered, with just over 1000 individuals remaining in the world, an outbreak could decimate the population. Simulation modeling was used to evaluate the potential impact of an Ebola virus outbreak on the mountain gorilla population of the Virunga Massif. Findings indicate that estimated contact rates among gorilla groups are high enough to allow rapid spread of Ebola, with less than 20% of the population projected to survive at 100 days post-infection of just one gorilla. Despite increasing survival with vaccination, no modeled vaccination strategy prevented widespread infection. However, the model projected that survival rates greater than 50% could be achieved by vaccinating at least half the habituated gorillas within 3 weeks of the first infectious individual.

Revisiting the baby schema by a geometric morphometric analysis of infant facial characteristics across great apes

Infants across species are thought to exhibit specific facial features (termed the “baby schema”, such as a relatively bigger forehead and eyes, and protruding cheeks), with an adaptive function to induce caretaking behaviour from adults. There is abundant empirical evidence for this in humans, but, surprisingly, the existence of a baby schema in non-human animals has not been scientifically demonstrated. We investigated which facial characteristics are shared across infants in five species of great apes: humans, chimpanzees, bonobos, mountain gorillas, and Bornean orangutans. We analysed eight adult and infant faces for each species (80 images in total) using geometric morphometric analysis and machine learning. We found two principal components characterizing infant faces consistently observed across species. These included (1) relatively bigger eyes located lower in the face, (2) a rounder and vertically shorter face shape, and (3) an inverted triangular face shape. While these features are shared, human infant faces are unique in that the second characteristic (round face shape) is more pronounced, whereas the third (inverted triangular face shape) is less pronounced than other species. We also found some infantile features only found in some species. We discuss future directions to investigate the baby schema using an evolutionary approach.

Assessing the drivers of illegal resource use to improve wildlife conservation interventions

Strategies to reduce illegal resource collection vary depending on the assumptions made about the underlying drivers of resource use. Interventions to reduce illegal resource use commonly include law enforcement, integrated conservation and development projects, and environmental education. Despite using a mixture of strategies, illegal activities continue to threaten the endangered mountain gorilla (Gorilla beringei beringei) in Volcanoes National Park (VNP), Rwanda. For conservation interventions to work effectively, it is important to understand the drivers of and motivations behind illegal resource use. To assess the drivers of, motivations behind, and deterrents to illegal resource use, we combined interviews of suspected illegal resource users with a larger household survey, indirect questioning (unmatched count technique), and focus groups. Overall, illegal resource use was most common among large households with lower well-being scores. Illegal resource users were more likely to report a problem from living near VNP and tended to be from households whose primary form of income was part-time labor. Although poverty was associated with illegal resource use overall, we found that several illegal resource users came from locally wealthy households and were motivated primarily by profit. Demand for forest products, like wild meat, highlights the structural factors likely behind illegal resource use and warrants further investigation. Because the drivers of illegal resource use varied between households, we find that neither law enforcement nor livelihood projects alone will decrease illegal resource use. Instead, effective conservation interventions require a multipronged approach to address the complex motivations of illegal resource use.

Past Connectivity but Recent Inbreeding in Cross River Gorillas Determined Using Whole Genomes from Single Hairs.

The critically endangered western gorillas (Gorilla gorilla) are divided into two subspecies: the western lowland (G. g. gorilla) and the Cross River (G. g. diehli) gorilla. Given the difficulty in sampling wild great ape populations and the small estimated size of the Cross River gorilla population, only one whole genome of a Cross River gorilla has been sequenced to date, hindering the study of this subspecies at the population level. In this study, we expand the number of whole genomes available for wild western gorillas, generating 41 new genomes (25 belonging to Cross River gorillas) using single shed hairs collected from gorilla nests. By combining these genomes with publicly available wild gorilla genomes, we confirm that Cross River gorillas form three population clusters. We also found little variation in genome-wide heterozygosity among them. Our analyses reveal long runs of homozygosity (>10 Mb), indicating recent inbreeding in Cross River gorillas. This is similar to that seen in mountain gorillas but with a much more recent bottleneck. We also detect past gene flow between two Cross River sites, Afi Mountain Wildlife Sanctuary and the Mbe Mountains. Furthermore, we observe past allele sharing between Cross River gorillas and the northern western lowland gorilla sites, as well as with the eastern gorilla species. This is the first study using single shed hairs from a wild species for whole genome sequencing to date. Taken together, our results highlight the importance of implementing conservation measures to increase connectivity among Cross River gorilla sites.

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.

The impact of tourist visits on mountain gorilla behavior in Uganda

ABSTRACT Tourism can play a significant role in the conservation of mountain gorillas (Gorilla beringei beringei) by financing the protection of their habitat, but few systematic studies have focused on the impacts of tourist presence on gorilla behavior. We assessed stress-coping mechanisms (Prosocial behaviors), behavioral indicators of stress (Self-scratching), and Human-directed behavior, in the presence and absence of tourist groups visiting one group of mountain gorillas living in Bwindi Impenetrable National Park, Uganda. Generalized linear mixed models were used to analyse differences in gorilla behavior as a function of (a) presence vs. absence of tourists and (b) proximity to tourists (3 m). Contrary to guidelines, tourists spent 60% of their viewing time within 3 m of the gorillas, and 96% of the tourist groups had more than 8 people. During tourist visits, gorillas increased time spent in Prosocial behavior and in rates of Self-scratching and Human-directed behavior. When tourists approached gorillas within 3 m, Prosocial and Human-directed behavior increased while Feeding decreased, but only adult males increased Self-scratching rates. We conclude that tourists are influencing gorilla behavior. We recommend following and enforcing the IUCN guidelines by keeping a minimum 7 m distance when viewing gorillas.

The Quality of Life and Perceived Human-Wildlife Conflicts among Forest Communities around the Mountain Gorilla’s Virunga Landscape in Africa

This article examines the relationships between human perceptions of conflict with wildlife and satisfaction with the quality of life in the Virunga landscape in Africa where mountain gorillas live. In addition, it explores how determinants of quality of life may indirectly influence the perceptions of conflict between people and wildlife. Using the bottom-up spillover theory of life satisfaction, it is hypothesized that quality of life is determined by access to critical livelihood resources, such as food, healthcare, and income. Furthermore, socio-psychological conditions, such as emotional and psychological strength, may mediate the relationship between access to resources and quality of life. This study revealed that life satisfaction positively predicts perceptions of conflict between humans and wildlife. The findings also indicated that health and psychological conditions were the strongest predictors of life satisfaction compared to food and financial security. However, the findings revealed variations by country. For example, food security predicts life satisfaction in Rwanda but not in Uganda. Health security predicts emotional wellbeing in Rwanda but not in Uganda. These results indicate that the nature of the relationship between wellbeing indicators and perceived Human-Wildlife conflict is likely country-specific. Therefore, efforts to strengthen the quality of life to indirectly advance wildlife conservation goals may need to be different in Uganda and Rwanda. The findings also suggest that investing in improving the quality of life of forest communities may incentivize increased perceptions of Human-Wildlife conflict. This is likely a result of pervasive consequences of increased funding for community development programs to incentivize conservation, which risks associating conflict with funding. Additional implications for practice and research are discussed in the paper.

Modularity of the wrist in extant hominines.

Wrist shape varies greatly across primates and previous studies indicate that the numerous morphological differences among them are related to a complex mixture of phylogeny and function. However, little is known about whether the variation in these various anatomical differences is linked and to what extent the wrist bones vary independently. Here, we used 3D geometric morphometrics on a sample of extant hominines (Homo sapiens, Pan troglodytes, Gorilla gorilla, and Gorilla beringei), to find the model that best describes the covariation patterns among four of the eight carpals (i.e., capitate, lunate, scaphoid, and trapezium). For this purpose, 15 modular hypotheses were tested using the Covariance Ratio. Results indicate that there is a covariation structure common to all hominines, which corresponds to stronger covariation within each carpal as compared to the covariation between carpals. However, the results also indicate that that there is a degree of codependence in the variation of some carpals, which is unique in humans, chimpanzees, and gorillas, respectively. In humans there is evidence of associated shape changes between the lunate and capitate, and between the scaphoid and trapezium. This covariation between lunate and capitate is also apparent in gorillas, while chimpanzees display the greatest disassociation among carpals, showing low covariation values in all pairwise comparisons. Our analyses indicate that carpals have an important level of variational independence which might suggest a high degree of independent evolvability in the wrists of hominines, and that although weak, the structure of associated changes of these four carpals varies across genera. To our knowledge this is the first report on the patterns of modularity between these four wrist bones in the Homininae and future studies might attempt to investigate whether the anatomical shape associations among carpals are functionally related to locomotion and manipulation.

Tourist expectations and satisfaction in mountain gorilla tourism in Bwindi Impenetrable National Park, Uganda

ABSTRACT Sustainable tourism plays a pivotal role in the conservation of endangered mountain gorillas (Gorilla beringei beringei); however, few studies have investigated tourist expectations and satisfaction from a tourism management perspective. We conducted a questionnaire survey (N = 303) from December 2019 to January 2020 in Bwindi, Uganda, and measured tourists’ expectations and satisfaction of 21 specific aspects on 5-point Likert scale. We also collected socio-demographic data and measured the overall satisfaction, recommendations to their friends and/or relatives, and the willingness to revisit on 10-point Likert scale. Tourists had high expectations, especially regarding observation experience, conservation, and education, while they had high satisfaction levels for most items, but with large variances in several aspects such as the costs and easiness of tracking. Mean satisfaction levels outweighed mean expectations in most items except for the sense of crowdedness and observation manner. The overall satisfaction and recommendation levels were very high but the willingness to revisit varied among tourists (negatively correlated with age), suggesting gorilla tourism is once in a lifetime experience for many tourists. The results indicated that mountain gorilla tourism performed well, but also highlighted implications for maintaining a sustainable tourism-conservation balance.

Mountain gorillas benefit from social distancing too: Close proximity from tourists affects gorillas' sociality

AbstractGorilla tourism supports the protection of its ecosystem, benefiting humans and wildlife populations living therein. Assessing to what degree the presence and proximity of tourists affect wildlife aids long‐term benefits. Because wild animals might see human activities as stressors, we hypothesized that the increased presence and proximity of tourists leads to immediate changes in gorilla social cohesion. We constructed social networks from association rates before, during, and after tourist visits, and when tourists were very close (≤3 m) or close (>3 m) to them. Our analysis focused on this distance threshold (≤3 m and >3 m) because the 7 m rule, enforced by the national park, was violated 84% of the time. We showed that gorillas spent more time in closer association after tourists arrived and when tourists were <3 m away from gorillas. Immediate changes were detected in the number of individuals close to each other, the time they spent together and the distance of an individual to all others, indicating that gorillas might increase social cohesion because they perceive tourists as a risk. These results highlight the need to enforce the tourism guidelines (maximum of eight people per group, including park staff; minimum distance of 7 m) to ensure the sustainable success of gorilla tourism.

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.

Association patterns of female gorillas.

Social interactions ultimately impact health and fitness in gregarious mammals. However, research focusing on the strength of affiliative interactions has primarily been conducted on female philopatric species. Gorillas provide an interesting counterpoint to previous research as females emigrate multiple times throughout their lives. We compare female-female association strength, duration and consistency in wild mountain (Gorilla beringei beringei) and western gorillas (Gorilla gorilla gorilla). Additionally, we examine whether the alpha male influences female association strength and if these associations are an artefact of both females concurrently in spatial proximity of the alpha male. In this between-species comparison, female gorillas had differentiated association patterns that were consistent on average for 2 years. The alpha males did not influence female association strength, with associations being similar in his presence or absence. Finally, we found more variability in association patterns among mountain gorillas with higher average association scores and higher proportion of 'preferred associates' than western gorillas. The rare dispersal pattern in the Gorilla genus may lead to greater flexibility in female association patterns than in species exhibiting female philopatry and strong kinship bonds. This may echo ancestral human society and provide new evidence to help us understand the evolution of modern human society. This article is part of the theme issue 'Cooperation among women: evolutionary and cross-cultural perspectives'.

Dominance in human (Homo sapiens) personality space and in hominoid phylogeny.

Unlike nonhuman primates, individual differences between humans in dominance do not appear as broad personality factors. This may be attributable to differences between the questionnaires used to study human and nonhuman primate personality. Alternatively, this may reflect differences in the organization of personality in humans and nonhuman primates. To determine which of these possibilities was most likely, 1,147 participants were recruited and asked to rate their personality and/or that of somebody else on the Hominoid Personality Questionnaire (HPQ), which has been used to study nonhuman primate personality. A large subset of these participants (~80%) also completed self- and/or rater reports of one of three questionnaires used to measure human personality. Exploratory factor analyses of HPQ rater report data yielded five factors. These factors correlated mostly in expected ways with scales from questionnaires used to study human personality. Exploratory factor analyses of HPQ self-report data yielded no clear number of factors and no consistent evidence with respect to the presence of a dominance factor. Subsequent analyses compared HPQ scales that represented dominance factors in chimpanzees, bonobos, mountain gorillas, and orangutans to scales derived from the Revised NEO Personality Inventory, including Fearless Dominance, which combined Neuroticism, Agreeableness, Conscientiousness, and Extraversion facets, Emotional Stability (the inverse of Neuroticism), and Extraversion's Assertiveness facet. Fearless Dominance and Assertiveness were most like the great ape dominance factors. The absence of human dominance factors, therefore, appears to reflect present or past social conditions of our species. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Exploring the Gorilla Trekking Safari and the Tourism Industry in Rwanda

The tourism industry in Rwanda has a high number of visitors each year. The research that is conducted in Rwanda's national parks mostly focuses on gorilla safari trekking, in particular mountain gorilla trekking. Destination scorned Even if there is a strategy in place to preserve the national parks, there are still threats such as poaching, shooting, bamboo gathering, and others. According to research conducted at Volcanoes National Park, Kagera National Park, and Nyungwe Tropical Vegetation, Rwanda has become the gorilla tourism destination of choice in Africa. This is significant when one considers the challenges faced by the critically endangered gorilla. We gathered the opinions of travelers and stakeholders involved in the gorilla tourism industry through the use of an online poll. Concepts about economics, society, culture, and the environment were investigated. Participants in the research were divided into three categories: stakeholders, visitors, and national actors so that stakeholder perspectives could be taken into account. To find out whether or not national citizens are aware of the significance of protecting parks to both the local park and the country as a whole. This paper will attempt to demonstrate how gorilla tourism has benefited the tourism industry in Rwanda. As a result of the efforts of the government to promote gorilla tourism on a global scale, the country has developed into an exciting tourist destination. On the show, the gorilla will be given a name, and Arsenal jerseys will be given their names. Keywords: Gorilla, Trekking, Rwanda tourism, highland, and Lowland gorilla DOI: 10.7176/JTHS/62-04 Publication date: November 30 th 2022

Ape femoral-humeral rigidities and arboreal locomotion.

This study investigates patterns of bone functional adaptations in extant apes through comparing hindlimb to forelimb bone rigidity ratios in groups with varying levels of arboreality. Using CT scans, bone rigidity (J) was calculated at three regions of interest (ROI) along femoral and humeral diaphyses in Homo, Pongo, Pan, and Gorilla with further comparisons made between species and subspecies divisions within Pan and Gorilla. Consistent with previous work on extant hominoids, species exhibited differences in midshaft femoral to humeral (F/H) rigidity ratios. Results of the present study confirm that these midshaft differences extend to 35% and 65% diaphyseal ROIs. Modern humans, exhibiting larger ratios, and orangutans, exhibiting smaller ratios, bracketed the intermediate African apes in comparisons. Within some African apes, limb rigidity ratios varied significantly between taxonomic groups. Eastern gorillas exhibited the highest mean ratios and chimpanzees the lowest at all three ROIs. In posthoc comparisons, chimpanzees and bonobos did not differ in relative limb rigidity ratios at any of the three ROIs. However, western gorillas were more similar to bonobos than eastern gorillas at 50% and 35% ROIs, but not at the 65% ROI. Species, and to a lesser extent subspecies, can be distinguished by F/H limb rigidity ratios according to broad positional behavior patterns at multiple regions of interest along the diaphyses. Similarity of bonobos and western gorillas is in line with behavioral data of bonobos being the most terrestrial of Pan species, and western gorillas the most arboreal of the Gorilla groups.

Cascading effects of social dynamics on the reproduction, survival, and population growth of mountain gorillas

AbstractWhilst the conservation impacts of density‐dependent population effects have been well studied, the impact that socially‐driven changes (e.g. group fissions that increase group density) can have on population growth in social species have only recently come to light. An increase in group density and intergroup encounters in a subpopulation of mountain gorillas Gorilla beringei beringei was shown to have driven a more than fourfold increase in infanticide, slowing population growth. In this study, we delve deeper into the consequences of these socially‐driven changes in group density, examining how patterns of reproduction and survival have changed in this subpopulation across more than 50 years. We show that adult female survival increased with strengthening conservation efforts early in the study, then remained stable, while age at first birth remained stable across the entire study. Interbirth intervals and female reproductive success did not vary significantly across time overall. However, socially‐driven increases in group density since the mid‐2000s appear to have had a cascade of effects. In addition to the increase in infant and adult male mortality from violence during intergroup encounters, higher encounter rates, and mortality were likely responsible for an increase in female transfers, which delayed reproduction. Females faced a 7.5‐month delay when transferring once and a 1.5‐year delay when transferring twice or more between births. We show these changes correspond with a 26.63% reduction in female reproductive success in 2007 to 2018, compared to 1994 to 2006, with females taking more than 2 years longer to produce an offspring that survived infancy. These findings demonstrate that social dynamics can have consequences for population growth beyond the immediate mortality effects of violent encounters. This further highlights the critical importance of social dynamics in the conservation of social species, particularly when populations are restricted to small or fragmented regions of habitat.

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.