Social behavior in primates varies widely within and across species, and growing work in behavioral genetics highlights the value of documenting sequence variation in neurobiologically relevant genes. However, for great apes, knowledge of individual genetic variation for behavior-associated loci remains limited. We characterized variation in the MAOA promoter VNTR and the OXTR SNP rs35062132 in 12 western lowland gorillas (Gorilla gorilla gorilla) and incorporated an exploratory comparison between genotypes and individual sociability. Sociability was quantified from 25 10-min focal follows per subject, including proximity, affiliative, and agonistic behaviors. We identified multiple MAOA VNTR genotypes, including a 0-repeat allele not previously reported in gorillas, indicating greater regulatory-region diversity than has been described for this species. No polymorphism was detected at OXTR rs35062132, although several fixed differences from other great ape species were identified at nearby nucleotide positions. Behavioral observations revealed individual differences in sociability; however, the presence of multiple previously undescribed MAOA VNTR genotypes with unknown functional consequences limited interpretability of genotype-behavior associations. We provide the first detailed description of MAOA promoter variation in gorillas and demonstrate sequence conservation in the OXTR region analyzed. These data underscore the importance of future research on gorilla social variation and comparative primate genomics.

Multimodal coordination of group departures in western gorillas

The distribution of African great apes has remained unconfirmed regarding their southern limit, particularly on the western side of the continent. IUCN maps include the Mayombe forest of Angola as part of the estimated distribution of western lowland gorillas (Gorilla gorilla gorilla) and central chimpanzees (Pan troglodytes troglodytes). However, until now, there were no records confirming the continued presence of both species. The Mayombe forest is a key biodiversity hotspot and a potentially important stronghold for the conservation of great ape populations in Africa. Here, we report the first systematic evidence of both species in the Mayombe National Park, Cabinda, Angola. In 2023, a grid of camera traps was systematically deployed, producing the first visual records of gorillas and chimpanzees. Building on these findings, in 2024, a pilot survey including ad libitum field observations was carried out along exploratory trails to maximise data collection. The combination of these records identified a hotspot of great ape activity where six transects were established, and systematic direct and indirect evidence was documented. Chimpanzees were recorded more times across a broader range of evidence categories, while gorillas appeared less and seemed more spatially restricted. Notably, both species were detected at overlapping sites but never simultaneously, indicating sympatric coexistence with spatio-temporal partitioning. These findings confirm the southernmost predicted distribution of both species for this part of Africa, filling critical gaps in the understanding of great ape evolution and biogeography, and providing a baseline for the first demographic and ecological census of great apes in Angola.

Understanding how ecological variation shapes skeletal morphology is important for linking observed locomotor behavior to anatomical correlates in extant hominoids, and for the subsequent interpretation of locomotor behavior in extinct taxa. In this study, we investigate ecomorphological variation in the metacarpals and phalanges across all five manual rays within Gorilla, focusing particularly on differences between western lowland gorilla (Gorilla gorilla gorilla) and the Rwandan (Volcanoes National Park) and Ugandan (Bwindi Impenetrable National Park) populations of mountain gorilla (Gorilla beringei beringei). This work incorporates the first substantial set of skeletal measurements from the Bwindi mountain gorilla population, derived from individuals recovered by the Mountain Gorilla Skeletal Project between 2018 and 2025. By comparing these data with samples from low and high-elevation Grauer's gorillas (Gorilla beringei graueri), we assess how variation in arboreality correlates with digit element lengths, demonstrating that the Bwindi mountain gorillas exhibit intermediate metacarpal and phalangeal lengths between the more arboreal western lowland gorillas and the more terrestrial Virunga mountain gorillas. These findings indicate a correlation between longer digital rays in more arboreal populations, even within the same species, which may enhance grasping and stability on arboreal substrates. We show a population-specific relationship between ecology and hand morphology in Gorilla and emphasize the value of documenting localized skeletal responses to environmental and behavioral variation to better interpret patterns in the hominoid fossil record.

Craniofacial fluctuating asymmetry (FA) in gorillas has been linked to environmental and/or genetic stress. Prolonged population declines increase levels of inbreeding, leading to developmental instability, which can manifest as FA. Among gorillas studied to date, craniofacial FA levels are highest in mountain gorillas (G. beringei beringei) and lowest in western lowland gorillas (G. gorilla gorilla), reflecting known levels of genetic diversity and inbreeding in these subspecies. This study assessed craniofacial FA in Cross River gorillas (G. gorilla diehli), a little-known subspecies with high levels of inbreeding due to a recent genetic bottleneck. Thirty fixed landmarks of the craniofacial skeleton were used to assess FA in 30 Cross River gorillas using Procrustes ANOVA. Principal component analysis assessed variation in both symmetric and asymmetric components. Differences in FA magnitudes between Cross River gorillas and published data for other Gorilla subspecies were assessed using permutation tests. Craniofacial FA accounts for 9.9% of shape variation in Cross River gorillas, whereas directional asymmetry accounts for 0.5%. Allometry accounts for 14.1% of shape variation in the symmetric component and 3.8% in the asymmetric component. Craniofacial FA magnitudes are higher in Cross River gorillas than in western lowland gorillas and lower than in mountain gorillas. High FA in Cross River gorillas aligns with known levels of inbreeding, supporting the link between genetic stress and craniofacial FA in gorillas. Persistent inbreeding and the loss of genetic diversity may decrease population fitness, further increasing the risk of extinction.

ABSTRACT Ecotourism based on animal habituation to human observers is an effective means for primate conservation while promoting local development. This may be difficult in areas with a history of poaching, as primates may still fear humans after poaching removal. Our study investigated the effectiveness of an ecotourism program involving the habituation of a group of 12 western gorillas ( Gorilla gorilla ) on Dipikar Island, Campo Ma'an National Park, Cameroon. During the habituation (2015–2022), we investigated the behavioural responses of gorillas to contact with observers in this geographically isolated area. This area had previously been exposed to consistent levels of poaching, today drastically reduced thanks to ongoing consistent anti‐poaching patrols. Aggressivity and fear decreased over time, while curiosity and visual time increased. Although the patterns of the gorillas' responses were similar to those observed in gorillas living in continuous forest without a history of poaching, habituation (> 8 years) lasted longer, as did the aggressive and avoidance responses. This was likely due to the past presence of poaching, rather than to its current low level: Habituation led to increased protection as the rare occurrence of poaching signs decreased with time. Our findings suggest the feasibility of ecotourism programs in areas previously affected by high anthropogenic pressure, provided this has been alleviated by continuous anti‐poaching protection.

ABSTRACT The current range of African great apes includes countries with some of the world’s highest incidence rates of human tuberculosis (TB). Non-human primates (NHPs) living in their natural habitats are expected to be free of TB. However, TB represents a known threat to captive NHP communities. We applied a non-invasive sponge-based environmental DNA (eDNA) sampling to run a cross-sectional survey at the human-animal interface in a challenging setting: the East of the Democratic Republic of Congo (DRC). The study sites included a primate rehabilitation centre, the local health area, and a nearby national park with critically endangered Eastern Lowland Gorillas (Gorilla beringei graueri). Sponge samples were tested for two PCR targets, IS6110 and mpb70. Positive samples were further characterized by spoligotyping, species identification and detection of molecular resistance against rifampicin and isoniazid. We detected Mycobacterium tuberculosis eDNA in 26% of the samples from all three sites including samples linked to humans, wild gorillas and captive NHPs. The spoligotype could be identified in 18 cases. Spoligotype SIT130 was detected in all sites including human and gorilla environment samples. These findings are strongly suggestive of epidemiological links between human and NHP TB in equatorial Africa.

Outbreaks of human respiratory syncytial virus in wild gorillas highlight the importance of prevention measures and integrated surveillance for risk mitigation

ABSTRACT Genetic diversity is a fundamental component of biodiversity and a conservation priority. Genetic studies on captive populations, vulnerable to genetic erosion, are therefore needed for long‐term conservation of threatened species. The western lowland gorilla ( Gorilla gorilla gorilla ) is considered Critically Endangered, but no major conservation genetic studies have been published on the captive gorilla population in the European Ex situ Programme (EEP). Here, using 10 microsatellite loci and mitochondrial DNA (mtDNA), we investigated the genetic diversity, genetic structure, signatures of inbreeding and taxonomic affinities of captive gorillas at Howletts and Port Lympne (HPL), conservation zoos holding ~10% of the EEP population and compared this with historical wild gorillas from the Powell‐Cotton Museum. High heterozygosity values and similar allelic richness were found in contemporary captive and historical wild populations, with no evidence of nuclear genetic diversity loss or inbreeding. However, contemporary captive gorillas had lower effective population size and mtDNA diversity than the historical wild population, and weak genetic differentiation from historical wild gorillas. All HPL gorillas showed expected taxonomic affinities to the subspecies G. g. gorilla . Our results demonstrate that captive breeding has successfully maintained heterozygosity and allelic richness (i.e., genetic diversity) as compared with a historical wild population, crucial for the evolutionary potential of this endangered primate. However, genetic differentiation between contemporary captive and historical wild gorillas likely reflects ~50 years of captive breeding starting from a small founder population sourced from various locations. The HPL population is genetically well placed to sustain future generations in captivity and the wild through conservation translocations, contributing to biodiversity goals.

The Western Lowland Gorilla, G. gorilla gorilla (Primate: Hominidae) is one of the largest living primates, maintained at Sri Chamarajendra Zoological Gardens, Mysuru (Latitude: 12.3028 N, Longitude: 76.6552 E).It is an exotic species, kept in a well maintained enclosure for public display for creating awareness among the public and for education, conservation and scientific studies.During the present study, after obtaining the permission from the higher authority, Sri Chamarajendra Zoological Gardens, Mysuru, proper planning

The prominent canine tooth of the large ape species western lowland gorilla (WLG; Gorilla gorilla gorilla), chimpanzee (CH; Pan troglodytes), bonobo (BO; Pan paniscus), and orangutan (ORG; Pongo pygmaeus spp.) is vulnerable to injury. Specialty consultation is often sought for severe dental fractures to optimize care. Although several options are possible (none, medical, endodontic, extraction), treatment by type of fracture for this tooth has not been well documented in apes. A retrospective review by survey was performed to assess the frequency of canine dental fracture in large apes that were managed in Association of Zoos and Aquariums Species Survival Plan© (SSP) holding institutions during 2004-2017. From 40 participating institutions, 13 facilities reported no canine tooth fractures in 96 individual apes (WLG, n = 40; CH, n = 18; BO, n = 0; ORG, n = 38). In the remaining 27 institutions, 108 individual apes (WLG, n = 55; CH, n = 45; BO, n = 6; ORG, n = 2) were reported with canine fractures. In these latter apes, 179 canine fractures were described; more than 1 canine was involved in 26 individual apes, contributing to 66% (n = 118) of the total fractures. The cause of these fractures was frequently unknown, but when identified, the most frequent cause was conspecific trauma. Dental fracture descriptions were standardized and then assessed in the context of the initial treatment selected. Classifications included fractures of the enamel (16%, n = 29), enamel-dentin (21%, n = 38), enamel-dentin-pulp (15%, n = 27), crown root (36%, n = 64), and root (9%, n = 17), or avulsion (2%, n = 4). Treatment categories included none (58%, n = 103), medical treatment (4%, n = 8), endodontic procedure (21%, n = 38), or extraction (17%, n = 30), which varied by initial presentation and species. From this retrospective review, understanding of canine dental fractures in large apes has been improved. The data collected inform veterinarians on prevalence and type of dental injury in large apes and support prospective improvement of their dental care.

The​‍​‌‍​‍‌​‍​‌‍​‍‌ Congo Basin, a globally significant forest with immense biodiversity, is gradually losing its continuous habitat due to the cutting down of trees, in addition to forest clearance, illegal logging, farming, and road and bridge construction activities. Over the last several decades, the Congo Basin has had a staggering loss of forest cover, with a rough estimate of 10 million hectares of forest being cleared between the year 2000 and 2025. The fragmentation interferes with natural processes and poses substantial difficulties to animal populations. Therefore, it is important to know how animals adjust and behave in fragmented areas so as to be able to conserve this ecosystem. This is research that makes use of Agent-Based Modeling (ABM) to investigate the behavioral changes of the key species in the Congo Basin, such as the western lowland gorilla, forest elephant, okapi, and chimpanzee, and to determine the effects that fragmentation has on the ecosystem's functionality. The present study will utilize an Agent-Based Approach (ABA) to simulate how habitat fragmentation will impact the daily routine, foraging behaviour, social interaction, reproductive success, The initial results reveal that fragmentation causes the movement range of forest elephants to be limited by 40%, group cohesion in gorillas reduced by 25%, and that breeding success in okapi has drastically gone down due to their being isolated. Additionally, the conservation model explores the impact of such conservation measures as wildlife corridors and protected areas to mitigate the harmful effects of fragmentation. The outcome of this research will be instrumental in improving the understanding of the intricate relationship between the animals and fragmented habitats in the Congo Basin. This knowledge serves as the foundation for conservation policy, making and planning to protect the rich biodiversity of one of the most vital ecosystems on the planet while tackling the escalating problem of habitat ​‍​‌‍​‍‌​‍​‌‍​‍‌fragmentation.

After gorillas were scientifically identified in the mid-19th century, it led to a ‘race’ to collect them for museums via colonial exploitative systems of nature for profit. Gorillas were hunted, dismembered, and forcibly brought to colonizing countries as ‘scientific specimens’. This paper documents a male gorilla who suffered at least two acts of violence for science, which ultimately resulted in his death. His remains were sold to an American museum in 1955, where they remain to this day. This individual testifies to the traumatic role museums played in the lives of gorillas. Besides the killing of gorillas, hunting may also disrupted the social structure and well-being of the surviving troop. The continuous retention of gorilla remains in the Europe and North America perpetuates colonialism, and thus, this paper urges the need for further decolonization among natural history museums.

Kahuzi-Biega National Park, in the eastern Democratic Republic of the Congo, currently hosts only 3,815 eastern lowland gorillas (Grauer’s gorillas) according to a recent survey conducted by the Wildlife Conservation Society (WCS) led by Dr. Andrew Plumptre. At higher altitudes, there are approximately 170 individuals of Grauer’s gorilla (Gorilla beringei graueri, Hominidae, Primates), including 143 regularly monitored as follows: 10 adult males, 58 adult females, 9 blackbacks, 20 sub-adults, 17 juveniles, and 29 infants, grouped into 9 semi-habituated families and 2 habituated families (the Chimanuka family and the Banonane family). The Chimanuka family consists of 1 dominant silverback male, adult females, blackbacks, sub-adults, juveniles, and infants. Visitor satisfaction also results from observing fresh nests built by the gorillas before their visit. Grauer’s gorillas build nests every night on the site. Our study aims to: (i) identify fresh nests built by Grauer’s gorillas in the different sectors of high altitude areas; (ii) characterize the dominant vegetative materials by layer and by season that show preference in the construction of nest types; (iii) determine the part of vegetative material most used in nest construction; (iv) assess the regenerative aspect of fruit trees at terrestrial nest sites by season; (v) identify the heights used in constructing different types of aerial nests and their pattern of habitat use by season. Using the method of reconnaissance walks, direct observation, and measuring the height of nests built on trees with a measuring tape by climbing the trees with a rope to assess the vertical distance between the base and the nests. EXCEL software was used to represent diagrams of nest types and the averages of the strata. The study was able to identify the areas visited by the Chimanuka family gorillas by season, with more areas visited during the rainy season than in the dry season. The categories of terrestrial and aerial nests showed that there were more terrestrial nests in the rainy season than in the dry season. Herbaceous strata were more visited during the rainy season, while in the dry season, gorillas more frequently slept in the shrub strata. Terrestrial nests are built in several categories; during the rainy season, they are mostly constructed from grasses (59%), and in the dry season, they are mostly made from shrub foliage (50%). 55% of ground nests are built by a dominant species, Mimulopsis solmsii, during the rainy season, and in the dry season, it is the species Chassalia subochreata (60%). Air nests are also built during both seasons: In the rainy season, gorillas construct nests at heights of 6 to 10 m, accounting for 55% of nests, and 40% of nests are built at heights of 1 to 5 m. The species Dombeya torrida is the most used tree for constructing aerial nests, followed by the shrub Galiniera coffeoides. In the dry season, 55% of nests are built at heights of 4 to 6 m and 40% at heights of 1 to 3 m. The shrub species Xymalos monospora is the most used, followed by Chassalia subochreata and the tree Trichilia volkensis.

Klinefelter's syndrome is the most prevalent sex chromosomal disorder in humans and has been observed in various mammalian species. This article documents the case of a 25-year-old western lowland gorilla (Gorilla gorilla gorilla) at Longleat Safari Park who was diagnosed with Klinefelter's syndrome. The study encompasses their diagnosis, behavioral assessment, and management strategies over twelve years. The behavioral profile includes neophobia, sensitivity to sounds, impaired problem-solving abilities, mood swings, and atypical social interactions. Management practices tailored to his condition involved establishing a consistent daily routine, mitigating exposure to sudden noises, and pre-emptive medical interventions at early signs of illness. These approaches have effectively addressed his unique needs and reduced stress-related behaviours. This case study underscores the necessity for individualized care plans for nonhuman primates with Klinefelter's syndrome, providing a guide for future management of similar cases in captivity. The findings contribute to the limited knowledge of Klinefelter's syndrome in gorillas and highlight the importance of personalized and consistent management strategies to enhance the welfare of affected individuals.

Many adenovirus (AdV) species have been isolated from human and non-human primates. Here we describe the isolation of a new AdV from a western lowland gorilla held captive in a zoo. Analysis of the genome sequence demonstrated that this virus is a member of the Mastadenovirus genus, but markedly distinct from all previously described species. The new virus, AdV-lumc014, has a relatively low DNA sequence identity (<90%) compared to other human and simian AdVs. The virus is most related to the HAdV-B and HAdV-E species, of which isolates were previously obtained from humans and apes (i.e. bonobos, chimpanzees, and western lowland gorillas). Phylogenetic analyses of the amino-acid sequences of the hexon, penton-base, fiber knob, protein IIIa, AdV polymerase, single-stranded DNA-binding protein, AdV protease, and protein IX confirmed the relationship with HAdV-B and HAdV-E. The phylogenetic distances exceed the value of 0.05 often used to separate distinct AdV species. In addition, we found evidence for recombination events between the AdV-lumc014 and HAdV-D. Almost no neutralizing immunity was detected in pooled human immunoglobulins, demonstrating that the virus is scarce or absent in the human population and that there is limited cross-reacting neutralizing immunity. This new AdV species may be a valuable expansion of the arsenal of AdVs that can be used for gene therapy, viral oncolysis, and as a vaccine carrier.

Abstract We examined the use of a paired stimulus preference assessment (PSPA) to identify preferred items of two adult male western lowland gorillas (Gorilla gorilla gorilla). Subsequently, we validated the most preferred items as reinforcers by assessing the gorillas’ participation in cooperative care-related daily training (also known as husbandry training) where these items were used. Frequency data were collected for the number of times each item was selected during preference assessments and the number of correct short-latency responses from the gorillas during the validation. Results indicate that items identified as preferred in the PSPA functioned as reinforcers for previously learned behaviors during training sessions. We describe the use of the PSPA as an efficient means of identifying potential reinforcers for husbandry training in the zoological setting and demonstrate an embedded methodology to validate the value of items selected frequently in a PSPA.

Abstract Central African great ape populations are in serious decline as a result of poaching, habitat loss and disease. Reliable estimates of population size are urgently needed for informed management action. We estimate the abundance and distribution of central chimpanzee Pan troglodytes troglodytes and western lowland gorilla Gorilla gorilla gorilla populations in the c. 11,000 km2 Dja-Ngoyla Complex in Cameroon, a critical component of the Tri National Dja-Odzala-Minkébé (TRIDOM) transboundary landscape, which covers 178,000 km2. We compare our results with previous site estimates and with other population estimates from the region. We completed 1,096.64 km of line transects (n = 559) in 2021 using the standing-crop nest counts method. The Dja-Ngoyla Complex supported c. 11,787 great apes. Chimpanzee abundance was significantly higher in Dja, and Ngoyla-Mintom supported 71% of the gorilla population. Thirty-seven per cent of the gorilla population and 17% of the chimpanzee population occurred in logging concessions. There was no significant change in the species’ abundance in Dja Faunal Reserve compared to our 2018 estimate using the same methodology. The chimpanzee population density was much higher in Dja and Ngoyla Faunal Reserves compared to other protected areas in the region. There was large variation in great ape densities across logging concessions, and those with implemented management certification schemes supported higher densities. This study also highlights the high risk of Dja’s great ape population becoming isolated. Promoting forest management certification to strengthen wildlife and habitat protection in all logging concessions in the Complex is urgently needed and will also allow local communities to benefit from these forests.

In primates, mothers are crucial for the survival and integration of young offspring into their social group. Usually, mothers adjust their behaviour to the offspring’s age and needs, but maternal experience might modulate developmental changes in such allocation. In this study, we conducted behavioural observations on 7 mother-offspring dyads of captive western lowland gorillas (Gorilla gorilla gorilla) to assess whether multiparous mothers adjusted to the changing requirements of their offspring differently from primiparous mothers, and better facilitated their social integration into the group. Our results showed that, compared to primiparous mothers, multiparous mothers were more likely in body contact with younger offspring and less with older offspring. However, maternal experience neither predicted nor mediated how likely mothers were to start or end body contact, nor did it mediate developmental changes in the offspring’s social behaviour toward other group members. Our study provides preliminary evidence of some limited differences in how primiparous and multiparous mothers allocate maternal behaviour in western lowland gorillas.

This case describes successful expectant management of pre-term pre-labor rupture of fetal membranes (PPROM) in a 20-year-old female western lowland gorilla (Gorilla gorilla gorilla). Rupture of fetal membranes occurred at estimated day 231 of gestation, prior to the birthing window (days 237-285) for this species. Expectant management consisted of broad-spectrum antibiotics, corticosteroids, and monitoring of the dam and fetus via serial ultrasonography, vital signs, and behavioral observation. The pregnancy was supported to term and completed with unassisted parturition of a healthy neonate at estimated day 250 of gestation. PPROM is a common complication reported in human pregnancy but has not been reported previously in gorillas in managed care. Expectant management was successful in this case and underscores the importance of operant conditioning which allowed for maternal and fetal monitoring. This case may serve as a reference for future management of similar conditions, benefiting breeding goals for this species.