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Extant great apes are characterized by a wide range of locomotor, postural and manipulative behaviours that each require the limbs to be used in different ways. In addition to external bone morphology, comparative investigation of trabecular bone, which (re‐)models to reflect loads incurred during life, can provide novel insights into bone functional adaptation. Here, we use canonical holistic morphometric analysis (cHMA) to analyse the trabecular morphology in the distal femoral epiphysis of Homo sapiens (n = 26), Gorilla gorilla (n = 14), Pan troglodytes (n = 15) and Pongo sp. (n = 9). We test two predictions: (1) that differing locomotor behaviours will be reflected in differing trabecular architecture of the distal femur across Homo, Pan, Gorilla and Pongo; (2) that trabecular architecture will significantly differ between male and female Gorilla due to their different levels of arboreality but not between male and female Pan or Homo based on previous studies of locomotor behaviours. Results indicate that trabecular architecture differs among extant great apes based on their locomotor repertoires. The relative bone volume and degree of anisotropy patterns found reflect habitual use of extended knee postures during bipedalism in Homo, and habitual use of flexed knee posture during terrestrial and arboreal locomotion in Pan and Gorilla. Trabecular architecture in Pongo is consistent with a highly mobile knee joint that may vary in posture from extension to full flexion. Within Gorilla, trabecular architecture suggests a different loading of knee in extension/flexion between females and males, but no sex differences were found in Pan or Homo, supporting our predictions. Inter‐ and intra‐specific variation in trabecular architecture of distal femur provides a comparative context to interpret knee postures and, in turn, locomotor behaviours in fossil hominins. [ABSTRACT FROM AUTHOR]

Three male Western lowland gorillas (Gorilla gorilla gorilla) were given the opportunity to select their own or conspecific photos on a touchscreen to indicate whether they wished the experimenter to deliver a food reward only to them or to them and the selected conspecific(s). This is only the second symbolic test of prosocial preferences with apes using a touchscreen, and the first with gorillas. The use of self and other photographs as symbols of prosocial choices was intuitive while controlling for the distraction of visible food rewards, and allowing for tests of transfer to further validate apparent prosocial intentions. Gorillas rapidly learned to avoid selecting a photograph of an empty enclosure that resulted in no rewards for any of the gorillas and transferred this learning to a novel photograph. The gorillas did not behave in a consistently self‐interested or prosocial manner but they clearly rejected the opportunity to choose spitefully. Their preferences for certain photographs did not necessarily reflect a preference to be prosocial toward that particular individual because these preferences did not transfer to novel photographs of the same individuals. The results call into question whether gorillas recognize themselves and conspecifics in photographs but cannot conclusively speak to whether gorillas have prosocial preferences. They do stress the importance of carefully probing alternative explanations when inferring intentions from observable behaviors. Highlights: This is the first study of prosocial preferences where subjects selected photographs of recipients on a touchscreen.Gorillas did not make primarily self‐interested or spiteful choices but they did not make consistently prosocial choices.Gorillas had preferences for particular photographs but preferences to reward particular recipients did not transfer across photographs.Gorillas may not have recognized their own images in photographs. [ABSTRACT FROM AUTHOR]

Balantioides coli (=Balantidium coli), a large ciliated protozoan, is reported in multiple free‐ranging and captive primate species, often in association with a clinical presentation that requires medical intervention. This report describes the clinical effectiveness of paromomycin sulfate against B.coli in zoo‐kept mandrill monkeys (Mandrillus sphinx, at orally doses of 8–31 mg/kg, once daily (SID) for 7 days) and gorillas (Gorilla gorilla gorilla, at orally doses of 1.4–3.1 mg/kg, SID for 5 days). [ABSTRACT FROM AUTHOR]

Ranging dynamics are physical and behavioral representations of how different socioecological factors affect an organism's spatial decisions and space use strategies. Western lowland gorillas (Gorilla gorilla gorilla) are a model species to investigate the drivers of spatial dynamics based on both the natural variation in socioecological factors within the species and compared with their mountain gorilla counterparts. In this study, we evaluate the influences of resource seasonality and social dynamics on variation in home range size, utilization, and intergroup overlap among multiple gorilla groups over an 8‐year study period in the northern Republic of Congo. This study shows that western lowland gorillas can have small home ranges comparable to mountain gorillas, rather than universally larger home ranges as previously supposed, and that home ranges are stable through time. The largest source of variation in space use was the degree of intergroup home range overlap. The study groups did not demonstrate intraspecific variation in range size nor changes in intergroup overlap with respect to seasonality of fruit resources, but all groups demonstrated expansion of monthly range and core area with group size, matching predictions of intragroup feeding competition. These findings highlight the potential impact of intergroup relationships on space use and prompt further research on the role of social dynamics in ranging strategies. In this study, we reveal a greater degree of variability and flexibility in gorilla ranging behavior than previously realized which is relevant to improving comparative studies and informing conservation strategies on behalf of these endangered primates. Research Highlights: Groups in this study had relatively smaller home range sizes than previous investigations on western lowland gorilla groups, with home range sizes more comparable to that of mountain gorilla groups.Western lowland gorilla home ranges were consistent with proposed foraging strategies but did not shift in size with the seasonality of fruit resources.Neighboring gorilla groups varied in degree of spatial overlap depending on the dyad of interest, with relationships in spatial overlap and utilization remaining consistent with the availability of fruit resources. [ABSTRACT FROM AUTHOR]

The anatomical underpinnings of primate facial expressions are essential to exploring their evolution. Traditionally, it has been accepted that the primate face exhibits a "scala natura" morphocline, ranging from primitive to derived characteristics. At the primitive end, the face consists of undifferentiated muscular sheets, while at the derived end there is greater complexity with more muscles and insertion points. Among these, the role of the human modiolus ("knoten" in German) has been emphasized. Recent studies have challenged this view by revealing significant complexity in the faces of several non‐human primates, thereby rejecting the linear notion of facial evolution. However, our knowledge of the facial architecture in gorillas, the second closest living relatives to modern humans, remains a significant gap in the literature. Here, we present new findings based on dissection and histological analysis of one gorilla craniofacial specimen, alongside 30 human hemifaces. Our results indicate that while the number and overall arrangement of facial muscles in the gorilla are comparable to those of chimpanzees and modern humans, several orofacial features distinguish the gorilla's anatomy from that of hominins. Among these are the absence of a modiolus, the continuity of muscular fibers over the region of the mouth corner, the flat (uncurving) sheet of the orbicularis oris muscle, and the insertion of direct labial tractors both anterior and posterior to it. Collectively, the anatomical characteristics observed in the gorilla suggest that the complex anatomy of the hominin face should be considered synapomorphic (shared‐derived) within the Pan‐Homo clade. [ABSTRACT FROM AUTHOR]

Objectives: Several theories have been proposed to explain the impact of ecological conditions on differences in life history variables within and between species. Here we compare female life history parameters of one western lowland gorilla population (Gorilla gorilla gorilla) and two mountain gorilla populations (Gorilla beringei beringei). Materials and Methods: We compared the age of natal dispersal, age of first birth, interbirth interval, and birth rates using long‐term demographic datasets from Mbeli Bai (western gorillas), Bwindi Impenetrable National Park and the Virunga Massif (mountain gorillas). Results: The Mbeli western gorillas had the latest age at first birth, longest interbirth interval, and slowest surviving birth rate compared to the Virunga mountain gorillas. Bwindi mountain gorillas were intermediate in their life history patterns. Discussion: These patterns are consistent with differences in feeding ecology across sites. However, it is not possible to determine the evolutionary mechanisms responsible for these differences, whether a consequence of genetic adaptation to fluctuating food supplies ("ecological risk aversion hypothesis") or phenotypic plasticity in response to the abundance of food ("energy balance hypothesis"). Our results do not seem consistent with the extrinsic mortality risks at each site, but current conditions for mountain gorillas are unlikely to match their evolutionary history. Not all traits fell along the expected fast‐slow continuum, which illustrates that they can vary independently from each other ("modularity model"). Thus, the life history traits of each gorilla population may reflect a complex interplay of multiple ecological influences that are operating through both genetic adaptations and phenotypic plasticity. [ABSTRACT FROM AUTHOR]

Spatial parameters and design of overnight housing spaces can have significant influences on both nocturnal and diurnal behaviors of western lowland gorillas (Gorilla gorilla gorilla) in captivity. This is especially true for bachelor groups, as adult males have demonstrated a greater tendency to separate from conspecifics overnight. Additionally, previous studies have suggested that the social needs of individuals in bachelor units may shift over time. The bachelor unit at the Detroit Zoo is managed in a unique hybrid strategy in which the group is housed socially for three nights (either indoors or indoors with outdoor access), then separately on the fourth. A 2016 study of this group (n = 3) suggested that individuals had better welfare following social overnight housing as compared to solitary overnight housing. We aimed to reassess how overnight housing conditions affect individual welfare several years later. We revised a previously developed qualitative behavioral assessment tool that included 13 behavioral items spanning both positive and negative indicators of welfare. Animal care staff completed the assessment and collected a fecal sample every day for each gorilla for a period of 3 months. We used Kruskal–Wallis tests to analyze variation in behavioral items and FGMs between conditions. We then used generalized linear mixed models to identify whether overnight housing condition or other potentially confounding variables were driving observed variation in welfare indicators. We found significant variation demonstrating significantly better welfare indicators after being housed separately as compared to being socially housed indoors overnight. Although separate housing appears to be the ideal condition for this group at this point in time, if seasonality permits, social housing with outdoor access may be a feasible alternative to consistent overnight separation for these gorillas. RESEARCH HIGHLIGHTS: All individuals in this case study demonstrated significantly better welfare indicators after being housed separately overnight as compared to being socially housed indoors overnight.A 2016 study of these gorillas suggested that individuals had better welfare following social overnight housing as compared to solitary overnight housing. This suggests that both ideal welfare conditions and the overnight social needs of male western lowland gorillas living in bachelor units may change over time.Most comparisons between being separately housed or socially housed with outdoor access overnight were nonsignificant, indicating that if seasonality permits, social housing with outdoor access may offer the same welfare benefits as overnight separation. [ABSTRACT FROM AUTHOR]

For regularly cycling primates in captivity, chemical contraceptives can be used to reduce the likelihood of unintentional offspring, but the effects on cyclic progesterone and sexual behavior have not been well studied in gorillas (Gorilla gorilla gorilla). As zoos are invested in maintaining naturalistic behaviors and physiology, this is an important aspect of gorilla physical and mental health. We examined how exposure to combination and progestin‐only oral birth control pills altered cyclic progesterone and timing of sexual behaviors in four female gorillas at four institutions compared to cycling controls. Hormonal data were collected using fecal steroid metabolites as detected by enzyme immunoassay. Behavioral data were collected via one‐zero sampling done by keeper staff. All methods of oral contraceptive eliminated the ovarian cycle, with fecal progestogens being maintained below baselines in cycling control individuals. There was also no evidence of any cyclic patterning in endogenous progesterone, suggesting that the methods tested do not allow for detection of a recovery of endogenous progesterone during a short no‐pill period. We also found that the oral contraceptives altered the timing of behavioral displays when compared to cycling control individuals but was not directly related to any fluctuations in endogenous progesterone. This study reveals a need for additional research on contraceptive use in gorillas and reinforces that sexual behavior in gorillas is both hormonally and socially mediated. Research Highlights: Captive housed female Western lowland gorillas were maintained on either combination or progestin‐only oral contraceptives.Progesterone metabolites were assessed in fecal materials and sexual behaviors were observed using a 1‐0 calendar.Oral contraceptive use eliminated any cyclicity in progesterone and altered timing of sexual behaviors in the gorillas. [ABSTRACT FROM AUTHOR]

Objectives: 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. Materials and Methods: 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. Results: 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. Conclusion: 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. [ABSTRACT FROM AUTHOR]

Great apes are threatened by many factors including habitat loss, forest degradation and disease. Despite the improved understanding of the distribution of gorillas in Cameroon, there is a lack of fine‐scale knowledge about their habitat use. We used the Kernel Density Estimate method combined with grid cell counting to assess gorilla distribution, habitat use and human disturbance on one of the least studied gorilla populations in Cameroon. Proportions of different habitat types in the landscape were quantified using classification and regression tree approach applied to Landsat‐8 and digital elevation model data. We found that the distribution of gorillas was restricted to the central band of the site (~22 km2). Although the area was dominated by mature forest, the goodness‐of‐fit test showed that gorillas used grassland areas more frequently. Intensive human activities were noted across the gorilla range, with used cartridge shells being the most evidence hunting sign. Our results can be used to guide conservation and sustainable development stakeholder decisions in the area. With increasing anthropogenic threats throughout the landscape, we recommend the implementation of noninvasive research activities focusing on threat monitoring, nesting and dietary ecology, and the promotion of community‐led conservation initiatives to reduce pressure on the gorilla habitat. [ABSTRACT FROM AUTHOR]

Recommendations for the successful management and maintenance of bachelor groups of western lowland gorillas (Gorilla gorilla gorilla) in zoological settings have been an increasingly prevalent focus within the zoological community. Over the past two decades, studies have examined the impact of various environmental factors on the stability of bachelor groups, proposed management strategies for bachelor groups, and compared behavioral trends between bachelor and mixed‐sex groups. These studies have clearly demonstrated that bachelor groups are complex social units that require specialized management approaches. In this study, we aimed to assess the extent to which bachelor group management across North American zoos accredited by the Association of Zoos and Aquariums aligns with established recommendations. We distributed a comprehensive survey broadly encompassing habitat and housing, aggression and wounding, group demographics, feeding, and training to the 22 zoos housing bachelor groups as of 2019. We received completed surveys from 19 zoos, representing a total of 21 social units and 59 individual gorillas. We used descriptive statistics to represent the range of current management strategies across the surveyed population and ANOVAs to assess significant variation in key demographic variables. Our results demonstrate that a majority of zoos have adopted the best practices for the formation of social groups established by Stoinski et al. in 2004. However, there is much less standardization across zoos in protocols surrounding training and feeding. Additionally, important variables in the assessment of wounding, such as time of day and location, are often unknown or not observed by animal care professionals. We highlight these two areas as being of particular focus in developing and adhering to consistent protocols across institutions. Highlights: A significant majority of current bachelor groups have followed the best practices for group formation and maintenance suggested by Stoinski et al. in 2004.While frequency and variety of feedings follow recommendations established within the Gorilla Care Manual, it may be beneficial to investigate schedule variability and its impact on group behavior.In light of the number of comprehensive wounding studies over the past five years, location and context offer future directions for investigation and may provide new management recommendations.The large degree of adherence to recommendations both from the AZA and scientific literature speaks to the efficacy of said recommendations, the continuous communication between institutions and the SSP, and the success of bachelor group management. [ABSTRACT FROM AUTHOR]

Rating scales, such as Likert scales, are incredibly flexible and intuitive tools for measuring individuals' rating of agreement with or relative preference for many types of stimuli. For humans, this typically involves ratings of agreement between end points representing distinct attitudes or beliefs; For example, strongly disagree to strongly agree. Nonverbal versions of Likert scales have also been presented to children, allowing them to indicate their degree of preference, pain, or happiness. However, before the current study, no known efforts had been made to develop a nonverbal rating scale for use with nonhuman animals. Such a scale would be a useful welfare tool, allowing nonverbal individuals to indicate not just relative preferences between pairs of items but their degree of liking for individual items. I present an outline of the steps taken to create such a scale for use with three zoo‐housed gorillas. Two gorillas succeeded in associating preferred and less preferred foods with different response buttons but none of the gorillas were able to effectively use the neutral response button. It is possible that limits in gorillas' capacity for conditional discriminations and/or conceptualization of constructs as abstract as "liking" impeded training. These data are relevant for understanding gorilla cognition and can inform continued efforts to create a tool for nonhumans to communicate their preferences to human caregivers in a more nuanced way than is currently possible. Research Highlights: I attempted to develop a nonverbal Likert scale for use with three zoo‐housed male gorillas using a conditional discrimination task.Two gorillas learned to use response buttons appropriately that denoted their individual preferred and less preferred food items.The gorillas did not learn to use the neutral button to denote food items that they did not strongly prefer.The conditional discrimination task based on abstract categories of preference was challenging for the gorillas to learn but shows promise for future development. [ABSTRACT FROM AUTHOR]

Western lowland gorillas (Gorilla gorilla gorilla) are Critically Endangered and show continued population decline. Consequently, pressure is mounting to better understand their conservation threats and ecology. Gastrointestinal symbionts, such as bacterial and eukaryotic communities, are believed to play vital roles in the physiological landscape of the host. Gorillas host a broad spectrum of eucaryotes, so called parasites, with strongylid nematodes being particularly prevalent. While these communities are partially consistent, they are also shaped by various ecological factors, such as diet or habitat type. To investigate gastrointestinal symbionts of wild western lowland gorillas, we analysed 215 faecal samples from individuals in five distinct localities across the Congo Basin, using high‐throughput sequencing techniques. We describe the gut bacterial microbiome and genetic diversity of strongylid communities, including strain‐level identification of amplicon sequence variants (ASVs). We identified strongylid ASVs from eight genera and bacterial ASVs from 20 phyla. We compared these communities across localities, with reference to varying environmental factors among populations, finding differences in alpha diversity and community compositions of both gastrointestinal components. Moreover, we also investigated covariation between strongylid nematodes and the bacterial microbiome, finding correlations between strongylid taxa and Prevotellaceae and Rikenellaceae ASVs that were consistent across multiple localities. Our research highlights the complexity of the bacterial microbiome and strongylid communities in several gorilla populations and emphasizes potential interactions between these two symbiont communities. This study provides a framework for ongoing research into strongylid nematode diversity, and their interactions with the bacterial microbiome, among great apes. [ABSTRACT FROM AUTHOR]

Objectives: This study examines the sensitivity of the development of the dorsal metacarpal ridge (DMR) to the frequency of knuckle‐walking during ontogeny in chimpanzees, and compares the prevalence and prominence of the DMR in hominoids and baboons. Materials and Methods: We characterized the type and frequency of quadrupedalism of wild chimpanzees of different ages from the Ngogo community, Uganda. Using museum specimens, we quantified third metacarpal DMR angle and height in Pan individuals of different developmental stages, and in adult Gorilla, Pongo, Hylobates, and Papio. Results: When terrestrial, all quadrupedalism consisted of knuckle‐walking, although older individuals knuckle‐walked more than younger. The total amount of quadrupedalism engaged in by different age groups while arboreal was consistent; however, knuckle usage while arboreally quadrupedal increased with age. The DMR ridge did not emerge in Pan until older infancy, after the onset of knuckle‐walking, and reached prominence by the juvenile stage. The DMR angle increased significantly after juvenility but relative height did not. Adult Pan and Gorilla have more prevalent and prominent DMRs than Papio; the DMR was rare in Pongo and absent in Hylobates. Discussion: The timing of development of the DMR in chimpanzees supports it as a knuckle walking character, as does its occurrence in gorillas, and virtual absence in suspensory orangutans and gibbons. The DMR in baboons differs in appearance and frequency from DMRs in African apes, and so differentiates knuckle‐walking from digitigrady in catarrhines. The relationship between the DMR and loading of a vertical hand while terrestrial deserves further study. [ABSTRACT FROM AUTHOR]

Objectives: Limb length and trunk proportions are determined in a large, taxonomically and environmentally diverse sample of gorillas and related to variation in locomotion, climate, altitude, and diet. Materials and methods: The sample includes 299 gorilla skeletons, 115 of which are infants and juveniles, distributed between western lowland (G. gorilla gorilla), low and high elevation grauer (G. beringei graueri), and Virunga mountain gorillas (G. b. beringei). Limb bone and vertebral column lengths scaled to body mass are compared between subgroups by age group. Results: All G. beringei have relatively short 3rd metapodials and manual proximal phalanges compared to G. gorilla, and this difference is apparent in infancy. All G. beringei also have shortened total limb lengths relative to either body mass or vertebral column length, although patterns of variation in individual skeletal elements are more complex, and infants do not display the same patterns as adults. Mountain gorillas have relatively long clavicles, present in infancy, and a relatively long thoracic (but not lumbosacral) vertebral column. Discussion: A variety of environmental factors likely contributed to observed patterns of morphological variation among extant gorillas. We interpret the short hand and foot bones of all G. beringei as genetic adaptations to greater terrestriality in the last common ancestor of G. beringei; variation in other limb lengths to climatic adaptation, both genetic and developmental; and the larger thorax of G. b. beringei to adaptation to reduced oxygen pressure at high altitudes, again as a product of both genetic differences and environmental influences during development. [ABSTRACT FROM AUTHOR]

The aims of this study were to determine the current prevalence of regurgitation and reingestion (R/R) and gain an insight on the occurrence of coprophagy in the Association of Zoos & Aquariums (AZA) gorilla (Gorilla gorilla gorilla) population. To do this, an online survey was sent to all AZA accredited gorilla institutions in 2018. This survey collected information on the severity of R/R at the individual level and the occurrence of coprophagy at the zoo level. Previous research suggests more than half of zoo‐housed gorillas in the North American population engaged in R/R and coprophagy to some extent. The current study had a 100% response and completion rate; data were collected on all 296 noninfant gorillas in the population. Responses indicated that 60% of the AZA gorilla population engages in R/R to some degree and 24% of the population are observed exhibiting coprophagy on a weekly basis. With this preliminary information on coprophagy, and the realization that the Zoo community has been unsuccessful at eliminating R/R over the past 30 years, the next steps should be aimed at empirically assessing the potential drivers of these behaviors. Continuing efforts to further understand and eliminate R/R and coprophagy in zoo‐housed primates is important not only because these behaviors are unsightly to visitors, but more importantly, R/R and coprophagy may signal deficiencies in current practices surrounding animal care. RESEARCH HIGHLIGHTS: Approximately two‐thirds of the AZA gorilla population engaged in regurgitation and reingestion (R/R) to some degree.Nearly a quarter of the AZA gorilla population were observed exhibiting coprophagy on a weekly basis.The Zoo community has been unsuccessful at eliminating R/R over the past 30 years, the next steps should be aimed at empirically assessing the potential drivers of the behavior. [ABSTRACT FROM AUTHOR]

Species distributions are influenced by processes occurring at multiple spatial scales. It is therefore insufficient to model species distribution at a single geographic scale, as this does not provide the necessary understanding of determining factors. Instead, multiple approaches are needed, each differing in spatial extent, grain, and research objective. Here, we present the first attempt to model continent‐wide great ape density distribution. We used site‐level estimates of African great ape abundance to (1) identify socioeconomic and environmental factors that drive densities at the continental scale, and (2) predict range‐wide great ape density. We collated great ape abundance estimates from 156 sites and defined 134 pseudo‐absence sites to represent additional absence locations. The latter were based on locations of unsuitable environmental conditions for great apes, and on existing literature. We compiled seven socioeconomic and environmental covariate layers and fitted a generalized linear model to investigate their influence on great ape abundance. We used an Akaike‐weighted average of full and subset models to predict the range‐wide density distribution of African great apes for the year 2015. Great ape densities were lowest where there were high Human Footprint and Gross Domestic Product values; the highest predicted densities were in Central Africa, and the lowest in West Africa. Only 10.7% of the total predicted population was found in the International Union for Conservation of Nature Category I and II protected areas. For 16 out of 20 countries, our estimated abundances were largely in line with those from previous studies. For four countries, Central African Republic, Democratic Republic of the Congo, Liberia, and South Sudan, the estimated populations were excessively high. We propose further improvements to the model to overcome survey and predictor data limitations, which would enable a temporally dynamic approach for monitoring great apes across their range based on key indicators. Highlights: We identified the Human Footprint and Gross Domestic Product as important indicators predicting African great ape density at the continental scale.Using site‐level abundance data, we predicted density and distribution for African great apes across their entire range. [ABSTRACT FROM AUTHOR]

Although individuals in some species refuse foods they normally accept if their partner receives a more preferred one, this is not true across all species. The cooperation hypothesis proposes that this species‐level variability evolved because inequity aversion is a mechanism to identify situations in which cooperation is not paying off, and that species regularly observed cooperating should be more likely to be averse to inequity. To rule out other potential explanations of inequity aversion, we need to test the converse as well: species rarely observed cooperating, especially those phylogenetically close to more cooperative species, should be less likely to be inequity averse. To this end, we tested eight zoo‐housed Western lowland gorillas (Gorilla gorilla gorilla) on a token exchange task in which subjects received either the same food reward or a less‐preferred reward for the same or more effort than their partner, recording both refusals to participate in the exchange and refusals to accept the reward. Supporting the cooperation hypothesis, even with procedural differences across sessions, gorillas were significantly more likely to refuse in all conditions in which they received a low‐value food reward after completing an exchange, regardless of what their partner received, suggesting that gorillas were not inequity averse, but instead would not work for a low‐value reward. Additionally, gorillas were more likely to refuse later in the session; while the pattern of refusals remained unchanged after accounting for this, this suggests that species should be tested on as many trials as is practical. Research Highlights: We tested Western lowland gorillas, a species that is rarely observed cooperating in the wild, on a token exchange paradigm in which reward and effort differed between the subject and the conspecific partner.Gorillas did not respond negatively to inequitable outcomes, but instead refused to participate in all conditions where they must put in effort to receive a low‐value reward. We also found that gorillas were more likely to refuse to participate later in a session.We discuss the implications for the cooperation hypothesis of the evolution of inequity aversion, as well as interesting future directions for research in responses to inequity. [ABSTRACT FROM AUTHOR]

Aim: Modelling African great ape distribution has until now focused on current or past conditions, while future scenarios remain scarcely explored. Using an ensemble forecasting approach, we predicted changes in taxon‐specific distribution under future scenarios of climate, land use and human populations for (1) areas outside protected areas (PAs) only (assuming complete management effectiveness of PAs), (2) the entire study region and (3) interspecies range overlap. Location: Tropical Africa. Methods: We compiled occurrence data (n = 5,203) on African apes from the IUCN A.P.E.S. database and extracted relevant climate‐, habitat‐ and human‐related predictors representing current and future (2050) conditions to predict taxon‐specific range change under a best‐ and a worst‐case scenario, using ensemble forecasting. Results: The predictive performance of the models varied across taxa. Synergistic interactions between predictors are shaping African ape distribution, particularly human‐related variables. On average across taxa, a range decline of 50% is expected outside PAs under the best scenario if no dispersal occurs (61% in worst scenario). Otherwise, an 85% range reduction is predicted to occur across study regions (94% worst). However, range gains are predicted outside PAs if dispersal occurs (52% best, 21% worst), with a slight increase in gains expected across study regions (66% best, 24% worst). Moreover, more than half of range losses and gains are predicted to occur outside PAs where interspecific ranges overlap. Main Conclusions: Massive range decline is expected by 2050, but range gain is uncertain as African apes will not be able to occupy these new areas immediately due to their limited dispersal capacity, migration lag and ecological constraints. Given that most future range changes are predicted outside PAs, Africa's current PA network is likely to be insufficient for preserving suitable habitats and maintaining connected ape populations. Thus, conservation planners urgently need to integrate land use planning and climate change mitigation measures at all decision‐making levels both in range countries and abroad. [ABSTRACT FROM AUTHOR]

The benzimidazole anthelmintic drug albendazole becomes metabolized to chiral albendazole sulfoxide, albendazole sulfone, albendazole 2‐aminosulfone, and other metabolites. High‐performance liquid chromatography with UV absorbance and fluorescence detection, liquid chromatography with mass spectrometry, and chiral electrokinetic chromatography were used to analyze albendazole metabolites in extracts of western lowland gorilla (Gorilla gorilla gorilla) plasma of patients with alveolar echinococcosis and the data are compared to those obtained with human patient samples and to those reported for other species in the literature. The data revealed that the albendazole sulfoxide to albendazole sulfone concentration ratio in gorilla plasma is significantly smaller compared to that in samples of men, rats, dogs, and cattle. It is, however, similar to what was observed in sheep and goats. The (+)‐albendazole sulfoxide to (−)‐albendazole sulfoxide enantiomeric ratio in gorilla blood determined by chiral electrokinetic chromatography was found to be >1 which is comparable to what was observed in humans, dogs, sheep, goats, and cattle but different to mice and rats. Furthermore, the electrokinetic chromatography data suggest that small amounts of albendazole 2‐aminosulfone may be present in plasma of gorillas and humans. The data gathered with the various separation‐based assays illustrate the value of technology featuring different analyte separation and detection principles. This is the first account describing aspects of the albendazole metabolism in gorillas. [ABSTRACT FROM AUTHOR]

Objectives: Weaning is a key life history milestone for mammals that represents both the end of nutritional investment from the perspective of mothers and the start of complete nutritional independence for the infants. The age at weaning may vary depending on ecological, social, and demographic factors experienced by the mother and infant. Bwindi mountain gorillas live in different environmental conditions and have longer interbirth intervals than their counterparts in the Virunga Volcanoes, yet other life history characteristics of this population remain less well known. We use long‐term data from Bwindi Impenetrable National Park, Uganda to examine factors related to weaning age. Materials and methods: We analyzed data on infants born in four mountain gorilla groups in Bwindi to quantify their age of weaning (defined as last nipple contact) and to test if the sex of offspring, parity, and dominance rank of mother influences age of weaning. We also compared the age at weaning and time to conception after resumption of mating in Bwindi and Virunga gorillas. Results: Bwindi gorillas were weaned at an average age of 57.5 months. No difference was found between age of weaning for primiparous and multiparous mothers, nor did maternal dominance rank influence age of weaning, but sons were weaned at a later age than daughters. The majority of Bwindi mothers were still suckling when they resumed mating and mothers generally conceived before they weaned their previous offspring. The age of weaning was significantly later in Bwindi than in Virunga gorillas. After mothers resumed mating, the time to conceiving the next offspring was not significantly longer for Bwindi females than Virungas females (6 vs. 4 months). Discussion Later weaning age for sons than daughters is similar to findings of other studies of great apes. Bwindi mountain gorillas are weaned at approximately the same age as western gorillas and chimpanzees, which is more than a year later than Virunga mountain gorillas. The results of this study suggest that variation in ecological conditions of populations living in close geographic proximity can result in variation in life history patterns, which has implications for understanding the evolution of the unique life history patterns of humans. [ABSTRACT FROM AUTHOR]

To determine the effectiveness of conservation strategies, not only should we monitor biological variables, such as population size and levels of illegal activity, but also we should examine changes in attitudes and behavior of local community members. Here, I use semistructured interviews of employees at two field sites, in Bwindi Impenetrable National Park, Uganda and Loango National Park, Gabon, to understand if their employment influenced their attitude towards gorillas and conservation and led to behavior change. In contrast to western views of gorillas as "gentle giants," staff viewed gorillas as dangerous animals before working for these projects. Overall, employment leads to viewing conservation and gorillas more positively, and in many cases, viewing the gorillas as kin. The most common value attributed to the gorillas was economic, yet intrinsic and non‐use existence values were frequently mentioned. Loango staff, but not Bwindi staff, reported behavior change related to hunting and bushmeat consumption, which likely is related to bushmeat consumption being commonplace in Gabon but not in Uganda. The Bwindi staff seemed to have a more positive and broader outlook toward conservation than the Loango staff, possibly because they had more years of formal education, they worked with gorillas longer, there is more history of conservation activities in Bwindi, and/or they have been less directly affected by negative consequences of conservation (e.g., crop raiding). This study shows the importance of explaining that gorillas are not dangerous if not provoked and using their human‐like characteristics as a means to change conservation values and interest of local communities, while concurrently recognizing that providing economic benefits and reducing negative effects of wildlife are a reality for conservation buy‐in. Research Highlights: Interviewing local employees of research projects can be useful because they are trained and work in a framework of science and conservation, yet have grown up in and live in local communities.Employment led to viewing conservation and gorillas more positively after working with gorillas directly.Explaining that gorillas are not dangerous and using their human‐like characteristics as a means to change conservation values and interest of local communities are important.Concurrently it is important to recognize that providing economic benefits and reducing the negative effects of wildlife are a reality for conservation buy‐in. [ABSTRACT FROM AUTHOR]

Objectives: Gorilla diets are characterized by large amounts of fruit and tough fibrous plant material. Hard‐object feeding is not generally associated with this genus as the high crests on their molar teeth would be at risk of damage from the mechanically challenging woody endocarp. This study aims to demonstrate that at least one population of western lowland gorillas are seasonal hard‐object feeders, orally processing the seeds of Coula edulis. Materials and methods: Feeding behavior of habituated western lowland gorillas and phenology of fruiting trees was observed over a 4‐year period to determine the extent they exploited the seeds of C. edulis. Additionally, the endocarps of C. edulis were subjected to testing to determine their mechanical properties. Results: Our results demonstrate that during the fruiting season (January, February, and December) gorillas consistently opened the seeds of C. edulis using their postcanine dentition. The protective endocarp is composed of a very stiff material, presenting a substantial mechanical challenge to a gorilla. However, the high ratio between elastic modulus and toughness will facilitate brittle, cataclysmic fracture of the seed shell given a high enough load. Discussion: Although a rich energy source, C. edulis likely tax gorilla dentitions to their upper limit. The rarity of such behavior at sites where it could be observed may indicate a degree of social learning or culture driving its occurrence. This shows a greater breadth of gorilla diets than previously described and suggests gorillas may be a useful model for interpreting the dietary mechanics that necessitated robust craniodental morphology in australopiths. [ABSTRACT FROM AUTHOR]

Objectives: Environmental and ecological factors, such as geographic range, anthropogenic pressure, group identity, and feeding behavior are known to influence the gastrointestinal microbiomes of great apes. However, the influence of individual host traits such as age and sex, given specific dietary and social constraints, has been less studied. The objective of this investigation was to determine the associations between an individual's age and sex on the diversity and composition of the gut microbiome in wild western lowland gorillas. Materials and Methods: Publicly available 16S rRNA data generated from fecal samples of different groups of Gorilla gorilla gorilla in the Central African Republic were downloaded and bioinformatically processed. The groups analyzed included habituated, partially habituated and unhabituated gorillas, sampled during low fruit (dry, n = 28) and high fruit (wet, n = 82) seasons. Microbial community analyses (alpha and beta diversity and analyses of discriminant taxa), in tandem with network‐wide approaches, were used to (a) mine for specific age and sex based differences in gut bacterial community composition and to (b) asses for gut community modularity and bacterial taxa with potential functional roles, in the context of seasonal food variation, and social group affiliation. Results: Both age and sex significantly influenced gut microbiome diversity and composition in wild western lowland gorillas. However, the largest differences were observed between infants and adults in habituated groups and between adults and immature gorillas within all groups, and across dry and wet seasons. Specifically, although adults always showed greater bacterial richness than infants and immature gorillas, network‐wide analyses showed higher microbial community complexity and modularity in the infant gorilla gut. Sex‐based microbiome differences were not evident among adults, being only detected among immature gorillas. Conclusions: The results presented point to a dynamic gut microbiome in Gorilla spp., associated with ontogeny and individual development. Of note, the gut microbiomes of breastfeeding infants seemed to reflect early exposure to complex, herbaceous vegetation. Whether increased compositional complexity of the infant gorilla gut microbiome is an adaptive response to an energy‐limited diet and an underdeveloped gut needs to be further tested. Overall, age and sex based gut microbiome differences, as shown here, maybe mainly attributed to access to specific feeding sources, and social interactions between individuals within groups. [ABSTRACT FROM AUTHOR]

Studies of femoral trabecular structure have shown that the orientation and volume of bone are associated with variation in loading and could be informative about individual joint positioning during locomotion. In this study, we analyse for the first time trabecular bone patterns throughout the femoral head using a whole‐epiphysis approach to investigate how potential trabecular variation in humans and great apes relates to differences in locomotor modes. Trabecular architecture was analysed using microCT scans of Pan troglodytes (n = 20), Gorilla gorilla (n = 14), Pongo sp. (n = 5) and Homo sapiens (n = 12) in medtool 4.1. Our results revealed differences in bone volume fraction (BV/TV) distribution patterns, as well as overall trabecular parameters of the femoral head between great apes and humans. Pan and Gorilla showed two regions of high BV/TV in the femoral head, consistent with hip posture and loading during two discrete locomotor modes: knuckle‐walking and climbing. Most Pongo specimens also displayed two regions of high BV/TV, but these regions were less discrete and there was more variability across the sample. In contrast, Homo showed only one main region of high BV/TV in the femoral head and had the lowest BV/TV, as well as the most anisotropic trabeculae. The Homo trabecular structure is consistent with stereotypical loading with a more extended hip compared with great apes, which is characteristic of modern human bipedalism. Our results suggest that holistic evaluations of femoral head trabecular architecture can reveal previously undetected patterns linked to locomotor behaviour in extant apes and can provide further insight into hip joint loading in fossil hominins and other primates. [ABSTRACT FROM AUTHOR]

Following the first descriptions of culture in primates, widespread agreement has developed that the term can be applied to nonhumans as group-specific, socially learned behaviors. While behaviors such as those involving extractive tool use have been researched intensively, we propose that behaviors that are more subtle, less likely to be ecologically constrained, and more likely to be socially shaped, such as cultural forms of communication, provide compelling evidence of culture in nonhuman primates. Additionally, cultural forms of communication can provide novel insights into animal cognition such as the capacity for conformity, conventionalized meanings, arbitrariness in signal forms, and even symbolism. In this paper we focus on evidence from studies conducted on wild great apes. First, we provide a thorough review of what exactly we do know, and by extension don't know, about great ape cultural communication. We argue that detailed research on both vocal and gestural communication in wild great apes shows a more nuanced and variable repertoire than once assumed, with increasing support for group-specific variation. Second, we discuss the relevance of great ape cultural communication and its potential for illustrating evolutionary continuity for human-like cultural attributes, namely cumulative culture and symbolism. In sum, a concerted effort to examine cultural forms of communication in great apes could reveal novel evidence for cultural capacities that have thus far been heavily debated in the literature and can simultaneously contribute to an improved understanding of the complex minds of our closest living relatives., (© 2023 The Authors. American Journal of Primatology published by Wiley Periodicals LLC.)

Background: Chronic rhinosinusitis is a common disease process in humans; however, in the primate population of gorillas, it has rarely been described. This case describes lifesaving sinus surgery on a critically ill gorilla performed by a human otolaryngology team in collaboration with the gorilla's veterinary medicine team. Methods: The 35‐year‐old western silverback gorilla was treated for 3 months with aggressive medical therapy for a worsening sinus infection. When his condition became severe, a computed tomography (CT) scan was performed showing advanced chronic rhinosinusitis with nasal polyps vs other masses and some bone erosion. As his condition deteriorated further, a tertiary otolaryngology team performed sinus surgery using the latest technology available, including image guidance, steroid‐eluting sinus stents, and balloon sinus dilation. The postoperative course was complicated by subcutaneous infection and eventual fistulization. Fortunately, with culture‐directed antibiotic therapy his condition gradually improved. One year later he required revision sinus surgery. At that point allergy testing was performed followed by appropriate allergy medical therapy. Now, 3 years out from his initial surgery, he continues to do well and has fathered a young female gorilla. Results: This case represents a unique collaboration between human physicians and veterinarians. The combined medical approach was critical to heal this ailing gorilla. This case discusses many of the challenges and offers recommendations for physicians who may be involved with similar care of animals in the future. Conclusion: The success of the surgical and medical treatment of this gorilla's life‐threatening sinus infection required many experts, careful planning, and corporate generosity. The interaction between human and animal medicine would not have been successful without the close and trusting collaborations between human and veterinary health providers. We encourage human healthcare providers to seek volunteer opportunities through their local zoos by engaging in discussions with their local veterinarians. [ABSTRACT FROM AUTHOR]

Objectives: The effects of phylogeny and locomotor behavior on long bone structural proportions are assessed through comparisons between adult and ontogenetic samples of extant gorillas. Materials and Methods: A total of 281 wild-collected individuals were included in the study, divided into four groups that vary taxonomically and ecologically: western lowland gorillas G. g. gorilla), lowland and highland grauer gorillas (G. b. graueri), and Virunga mountain gorillas G. b. beringei). Lengths and articular breadths of the major long bones (except the fibula) were measured, and diaphyseal cross-sectional geometric properties determined using computed tomography. Ages of immature specimens (n = 145) were known or estimated from dental development. Differences between groups in hind limb to forelimb proportions were assessed in both adults and during development. Results: Diaphyseal strength proportions among adults vary in parallel with behavioral/ecological differences, and not phylogeny. The more arboreal western lowland and lowland grauer gorillas have relatively stronger forelimbs than the more terrestrial Virunga mountain gorillas, while the behaviorally intermediate highland grauer gorillas have intermediate proportions. Diaphyseal strength proportions are similar in young infants but diverge after 2 years of age in western lowland and mountain gorillas, at the same time that changes in locomotor behavior occur. There are no differences between groups in length or articular proportions among either adults or immature individuals. Conclusion: Long bone diaphyseal strength proportions in gorillas are developmentally plastic, reflecting behavior, while length and articular proportions are much more genetically canalized. These findings have implications for interpreting morphological variation among fossil taxa. [ABSTRACT FROM AUTHOR]

Case description A 17-year-old female western lowland gorilla presented with bilateral ocular discharge, conjunctivitis, and rhinitis that was investigated and treated over a 34-month period. Clinical findings, diagnostic results, treatment, and follow-up are described. Clinical finding A mild intermittent mucoid ocular discharge was initially noted. 10 months later, conjunctival hyperemia and thickening developed and progressed rapidly to a mass-like lesion covering the right eye. Hematology revealed eosinophilia. Conjunctival cytology revealed eosinophils and neutrophils, and histopathology revealed a chronic proliferative eosinophilic conjunctivitis. 21 months after, the ocular lesions were investigated the gorilla developed masses within both external nares. Histopathology of the nasal lesions revealed chronic-active eosinophilic rhinitis. Treatment and outcome Treatment of the gorilla was based on protocols recommended for human patients. Protocols for mild, moderate, and finally severe disease were used, involving topical and oral combinations of treatments. The gorilla eventually responded to systemic immunosuppressant therapy recommended for severe refractory disease. Clinical significance To the authors' knowledge, this is the first reported case of vernal-like conjunctivitis in a western lowland gorilla. [ABSTRACT FROM AUTHOR]

Applying environmental education in primate range countries is an important long-term activity to stimulate pro-conservation behavior. Within captive settings, mega-charismatic species, such as great apes are often used to increase knowledge and positively influence attitudes of visitors. Here, we evaluate the effectiveness of a short-term video and theater program developed for a Western audience and adapted to rural people living in two villages around Nouabalé-Ndoki National Park, Republic of Congo. We assessed the knowledge gain and attitude change using oral evaluation in the local language ( N = 111). Overall pre-program knowledge about Western gorillas ( Gorilla gorilla) was high. Detailed multivariate analysis of pre-program knowledge revealed differences in knowledge between two villages and people with different jobs while attitudes largely were similar between groups. The short-term education program was successful in raising knowledge, particularly of those people with less pre-program knowledge. We also noted an overall significant attitude improvement. Our data indicate short-term education programs are useful in quickly raising knowledge as well improving attitudes. Furthermore, education messages need to be clearly adapted to the daily livelihood realities of the audience, and multi-variate analysis can help to identify potential target groups for education programs. [ABSTRACT FROM AUTHOR]

Films, as part of a larger environmental education program, have the potential to influence the knowledge and attitudes of viewers. However, to date, no evaluations have been published reporting the effectiveness of films, when used within primate range countries as part of a conservation themed program. The Great Ape Education Project was a year-long environmental education program implemented in Uganda for primary school students living adjacent to Kibale National Park (KNP) and Bwindi Impenetrable National Park (BINP). Students viewed a trilogy of conservation films about great apes, produced specifically for this audience, and participated in complementary extra-curricular activities. The knowledge and attitudes of students participating in the program from KNP, but not BINP were assessed using questionnaires prior to ( N = 1271) and following ( N = 872) the completion of the program. Following the program, students demonstrated a significant increase in their knowledge of threats to great apes and an increase in their knowledge of ways that villagers and students can help conserve great apes. Additionally, student attitudes toward great apes improved following the program. For example, students showed an increase in agreement with liking great apes and viewing them as important to the environment. These data provide evidence that conservation films made specifically to address regional threats and using local actors and settings can positively influence knowledge of and attitudes toward great apes among students living in a primate range country. [ABSTRACT FROM AUTHOR]

Differences in macronutrients between human and ape milks appear relatively small, but variation in other components such as immunoglobulins (Ig) may be greater. This study characterized the macronutrient and secretory (sIgA) profiles in milk from gorillas and orangutans throughout lactation. Fifty-three milk samples from four gorillas and three orangutans were collected throughout 48 and 22 months postpartum (MPP), respectively. Samples were grouped in five stages of lactation (0 to 6 months, more than 6 months to 12 months, more than 12 months to 18 months, more than 18 months to 36 months, and more than 36 months to 48 months). Data were analyzed as a complete randomized design. Concentration of sIgA did not change due to species or its interaction with MPP. Crude protein, regardless of MPP, was greater for gorillas compared with orangutans (1.27 vs. 0.85%). Fat, sugar, and gross energy were affected by the interaction of species × MPP. For gorilla milk, concentrations of sIgA were 43 mg/L at 6 MPP increasing to 79 mg/L at 48 MPP. Protein was highest at 48 MPP. Sugar was lowest at 48 MPP. Values for fat and gross energy were the highest 36 MPP. For orangutan milk, concentrations of sIgA were highest at 6 MPP. Sugar decreased with MPP. Protein, dry matter, or fat were unaffected by MPP. Gross energy content was steady during the first 18 MPP but it tended to decrease by 36 MPP. The results indicate that macronutrients are similar between human, published data, and great ape milk, though gorilla milk has higher protein and human milk higher fat (published data). Concentrations of sIgA in ape milk were about 10-fold lower than human values from the literature. Differences between human and ape milk may lie more in bioactive/immune molecules than nutrients. RESEARCH HIGHLIGHTS Milk macronutrients from great apes differed throughout lactation., Milk macronutrients but not IgA from non-human great apes and humans were quite similar., Milk protein was greater in Gorilla compared with Orangutan. [ABSTRACT FROM AUTHOR]

In this article, I describe a previously unreported maxillary lateral incisor defect (MLID) of the enamel in great apes and evaluate potential general causes (genetic, systemic stress, or localized disturbance), as well as examine differences in prevalence among the represented taxa. This defect occurred only on the labial surface of the maxillary lateral incisor and extended from the cervical-mesial quarter of the crown to the mesial edge of the cementoenamel junction (CEJ). The study sample consisted of 136 great ape specimens, including 41 gorillas, 25 chimpanzees, and 70 orangutans from the Smithsonian's National Museum of Natural History great ape collection. I used logistic regression to assess the prevalence of this defect in the sample and a binomial probability test for bilaterality. This defect of the maxillary lateral incisor is the second most common defect I observed in the study sample (30.1% of individuals affected), and was more likely to occur in individuals with linear enamel hypoplasia (LEH) and pit defects than those without these defects. Among specimens with both maxillary lateral incisors present, the defect was mostly bilateral. Pan and Pongo were significantly more likely to exhibit the defect than Gorilla. Between Pongo species, Pongo pygmaeus was significantly more likely to exhibit the defect than Pongo abelii. Between subspecies of Gorilla, although Gorilla gorilla gorilla exhibited the defect and Gorilla gorilla beringei did not, the difference was not significant. No sex differences were evident in this sample. The prevalence of this defect indicates it is not hereditary. The bilateral trend indicates a systemic cause, although the high inter-tooth specificity suggests a local disturbance and a combination of both is possible. [ABSTRACT FROM AUTHOR]

The ability to accurately measure morphological characteristics of wild primates in the field is challenging, yet critical for understanding fundamental aspects of their biology and behavior. Recent studies have shown that digital photogrammetry can be used to non-invasively measure morphological traits of wild primates, as it allows for the determination of geometric properties of objects remotely from photographic images. We report here on a rare opportunity to test this methodology by comparing measurements obtained directly from living great apes to those obtained from photographs. We test the accuracy and precision of two independent photogrammetric techniques, employing the use of parallel lasers and a distance meter, respectively, for obtaining measurements of static objects and captive western lowland gorillas ( Gorilla gorilla gorilla) ( n = 4) at Zoo Atlanta. For static objects, the mean percent error between corresponding measurements collected by the same observer directly versus using photogrammetry was 0.49-0.74% for the parallel laser method and 0.62-0.76% for the distance meter method. For gorillas, mean percent error between corresponding direct and remote measurements was 2.72-5.20% for the parallel laser method and 2.20-7.51% for the distance meter method. Correlations between direct measurements and corresponding parallel laser and distance meter measurements of gorillas were highly significant with R2 values and slopes approaching 1.0 (parallel lasers: R2 = 0.9989, P < 0.0001; distance-meter: R2 = 0.9990, P < 0.0001). Further, variation between measurements of the same targets collected repeatedly by the same observer, and between different observers, was uniformly low across methods (CV, range = 0.003-0.013). While errors are slightly higher for the distance meter technique, both methods show great promise for addressing a wide range of questions requiring the non-invasive collection of morphological data from wild primates. Am. J. Primatol. 78:418-431, 2016. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Close distance vocalizations are an integral part of primate vocal communication. They exhibit large acoustic variation which has been suggested to constitute flexible responses to the highly variable social setting of group living animals. However, a recent study suggested that acoustic variation in close distance calls of baboons may also arise from acoustic adaptations to environmental factors in order to counteract sound degradation. We tested whether the variation in calling rate and acoustic structure of gorilla close distance vocalizations may serve to counteract distorting effects of vegetation during sound propagation. Using focal animal sampling we recorded the vocal behavior of 15 adult individuals living in two groups: one group of western lowland gorillas Gorilla gorilla gorilla and one group of mountain gorillas Gorilla beringei beringei. We considered the distance between the caller and its nearest neighbor as the minimum transmission distance of calls; while vegetation density was quantified through measures of visibility. Our analysis revealed vocal plasticity in gorilla close calls in relation to changes in visibility and nearest neighbor distance. However, the observed changes in fundamental frequency and calling rate are unlikely to counteract degrading effects of vegetation, but rather seem to reflect reactions to variation in spatial and visual separation from other group members, similar to the audience effects demonstrated in a range of other species. We propose that vocal plasticity to counteract distorting environmental effects may not be prevalent across taxa and perhaps confined to species living in heterogeneous habitats with highly variable transmission conditions. Am. J. Primatol. 77:1239-1252, 2015. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

ABSTRACT Objectives Analyses of hominine forelimb diaphyseal structure typically employ sections located at midshaft. This study addresses three questions. First, how accurately must midshaft be defined to yield comparable data? Second, does variation in midshaft location due to alternative definitions fall within error ranges such that data gathered using different length measurements are comparable? Third, do error ranges and length metric effects differ between elements or taxa such that certain bones or species are more prone to issues of comparability? Materials and Methods Humeri, radii, and ulnae of Homo, Pan, and Gorilla were CT-scanned at full length and error ranges for three structural parameters (CSA, J, Imax/ Imin) were calculated around midshafts. Results Distances proximally and distally from midshaft where structural values become significantly different from midshaft values vary between elements, taxa, and structural parameters. Error ranges are largest for the humerus and smallest for the ulna. Among taxa, error ranges for gorillas are largest and those for humans are smallest. Among structural parameters, error ranges depend on element and taxon such that no parameter consistently exhibits larger or smaller error ranges across all bones or species. Variation in midshaft locations originating from different length definitions is small and falls within error ranges defined by maximum length across all elements and taxa. Discussion Including fragmentary specimens for which midshaft location is uncertain in comparisons of forelimb diaphyseal structure requires evaluation on a case-by-case basis, with consideration to element, taxon, and structural traits of interest. However, midshaft data for all three structural parameters considered here that are recorded using different length measurements can be reasonably compared. Am J Phys Anthropol 158:386-397, 2015. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

ABSTRACT Objectives In comparative analyses of hominine hind limb diaphyseal structure, homologous cross sections are located according to half bone length (midshaft). Here, we address three questions. First, how accurately must midshaft be defined to yield comparable data? Second, does variation in midshaft location due to different ways of measuring length fall within error ranges such that data gathered using different metrics are comparable? Third, do error ranges and length metric effects differ between elements or taxa such that certain bones or species are more prone to issues of comparability? Materials and Methods Femora and tibiae of Homo, Pan, and Gorilla were CT-scanned longitudinally and error ranges for multiple structural parameters (CSA, J, Imax/ Imin) were calculated around midshafts. Results Distances proximally and distally from midshaft where structural values differ significantly from midshaft values vary between bones, species, and structural traits. Femoral error ranges are typically larger than tibial ranges. In the femur, error ranges are generally largest for chimpanzees and smallest for gorillas. A similar taxonomic pattern is not evident in the tibia. No structural trait consistently displays larger or smaller error ranges across both elements and all species. Variation in midshaft locations stemming from different length definitions is small and falls within observed error ranges defined by any one metric. Discussion Incorporating fragmentary specimens (e.g., fossils) for which midshaft location is unknown in comparisons of diaphyseal structure necessitates evaluation on a case-by-case basis, with thought to element, taxon, and structural traits of interest. Midshaft data recorded from distinct length measurements are generally comparable. Am J Phys Anthropol 158:398-407, 2015. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

ABSTRACT Objectives The premolar sub-cervical region in four non-human extant ape genera are examined to: 1) define a classification scheme for the premolar root system in order to rigorously characterize, quantify and document variation in root and canal, form, number and configuration; 2) compare this variation within and between genera; and 3) test the hypotheses that sex and size (i.e., the 'size/number continuum,' Shields, ) of the premolar are determinants of root/canal form and/or number. Materials and Methods Microtomography and 3D visualization software are utilized to examine a large sample of Hylobates, Pan, Gorilla, and Pongo ( n = 951 teeth). Each premolar root system is examined to ascertain the expected level of variability for each taxon. Cervical surface area (mm2) serves as a metric proxy for tooth size. A Chi-square test of independence is used to assess for variability differences between and within each taxon, and Mann-Whitney U tests are employed to assess the predicted relationship between tooth size and variation within each taxon. Results Our findings indicate that root and canal configurations, non-metric root traits and tooth size can distinguish between extant ape genera. Within the four ape taxa, premolar size variation is generally, but not always, correlated with canal/root number. Our results indicate that males and females within genera differ in tooth size but not in canal/root form and number. Discussion We report previously undocumented variation in the study taxa. Our results are discussed within the context of Miocene Apes as well as the developmental and systematic implications. Am J Phys Anthropol 158:209-226, 2015. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

In North American zoos, male gorillas are often housed in all-male (bachelor) groups to provide socialization for males not managed in breeding groups. These groups exhibit long-term cohesion and stability and males in bachelor groups are no more aggressive than males in mixed-sex groups. Previous studies have shown that aggression in male gorillas is more directly related to age rather than group type, with young silverbacks (YSB; males 14-20 years of age) having higher rates of aggressive behavior than males of other age classes. Despite this, anecdotal reports have persisted that bachelor groups have higher wounding rates than mixed-sex groups. To assess wounding in zoo-housed gorillas, all instances of wounding across 28 zoos (180 gorillas, 45 social groups) were recorded over a 26 months period via a standardized data sheet. Similar to previous reports, we found age to be an important determinant in wounding. Bachelor groups that contained YSB's had significantly more wounds than bachelor groups without YSB's ( U = 14.0, z = −2.193, P = 0.029). There was no difference in wounding rates between mixed-sex and bachelor groups without YSB's ( U = 69.5, z = −0.411, P = 0.689). These data further demonstrate the importance of behavioral management of YSB's in zoos and the viability of bachelor groups as a long-term housing solution for male gorillas. Zoo Biol. 34:296-304, 2015. © 2015 Wiley Periodicals Inc. [ABSTRACT FROM AUTHOR]

In humans, Cryptococcus mainly infects individuals with HIV infection or other types of immunosuppression. Here, we report the first case of disseminated cryptococcosis in a simian immunodeficiency virus-negative 27-year-old female Gorilla gorilla presenting with lethargy, progressive weight loss and productive cough. The diagnosis was confirmed by positive lung biopsy culture, serum cryptococcal antigen, and cerebral histopathology demonstrating encapsulated yeasts. Molecular characterisation of lung culture isolate yielded Cryptococcus neoformans var. grubii. An immune-deficiency could not be demonstrated. [ABSTRACT FROM AUTHOR]

I examined human-animal relationships (HARs) in zoo-housed orangutans ( Pongo abelii) and gorillas ( Gorilla gorilla gorilla) to see if they followed patterns similar to conspecific relationships in great apes and humans. Familiarity and social relationships guide humans' and great apes' behaviors with conspecifics. Inter-individual relationships, based on shared social history, and 'generalized' relationships, based on a history of interactions with relevant classes of individuals, guide behavior with familiar and unfamiliar conspecifics, respectively. I examined whether both familiarity and social relationships similarly guides great apes' cross-species interactions with humans. I used repeated measures MANOVA to compare hourly rates and average durations of ape-initiated human-directed behaviors (HDBs) between familiar and unfamiliar humans and between great ape species. HDB patterns were consistent with familiarity-based HAR predictions, indicating more negative relationships with unfamiliar humans and more positive relationships with familiar humans. Findings for unfamiliar humans are consistent with negative effects of humans on apes' behavior reported in traditional visitor effect studies (VES). However, findings for familiar humans may be overlooked in VES due to pooling across levels of human familiarity or failure to consider humans other than primarily unfamiliar visitors. Additionally, species differences in apes' HDBs suggest that data pooling across species, common in many zoo studies, may mask important differences. These findings have important methodological implications for studies of human-animal interaction as well as for captive animal wellbeing. Am. J. Primatol. 76:942-955, 2014. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine the personality structure of eight male gorillas (five silverbacks and three blackbacks) housed at the Sedgwick County Zoo in Wichita, Kansas and to determine if personality predicts behavior and subjective well-being in male gorillas living in bachelor groups. We used the Hominoid Personality Questionnaire which contains 54 descriptive adjectives with representative items from the human five-factor model. Rates of 12 behaviors that are broadly defined as agonistic or affiliative were independently recorded and calculated. Principal components analysis yielded three reliable personality factors: Dominance, Extraversion/Agreeableness, and Conscientiousness. These results are the first potential quantitative evidence for a Conscientiousness factor in a hominoid other than chimpanzees and humans. This suggests that Conscientiousness originated with the common ancestor of male gorillas and humans around 10 million years ago. These results indicate that humans can reliably assess the personality and subjective well-being of captive male gorillas living in bachelor groups with robust levels of inter-rater reliability and validity. Furthermore, personality can accurately predict behavior ( r = 0.79; n = 13) and subjective well-being ( r = 0.83; n = 5) in gorillas and provide convergent and discriminant validity for the personality factors. The results advocate for the use of personality questionnaires in the captive management of bachelor gorillas over long-term multi-institutional behavioral studies. Am. J. Primatol. 76:879-889, 2014. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The successful management of captive animals requires attention to multiple interconnected factors. One critical aspect of the daily life of a captive animal is the recommended and/or provisioned diet. This study focuses on the diets of zoo-housed gorillas. A national survey of diets among zoo-housed gorillas was conducted to examine diets being offered to captive gorillas in the United States and Canada. This survey serves as a follow-up to a 1995 dietary survey of zoo-housed gorillas and goes further to quantify nutritional profiles at responding institutions. Results are encouraging, as zoos have made clear improvements in dietary nutrient profiles offered over the past 15 years. However, we suggest that zoological and sanctuary institutions follow Gorilla Species Survival Plan (SSP) recommendations and work to continuously improve diets provided, which could improve gorillas' health and well-being. Zoo Biol. 33:419-425, 2014. © 2014 Wiley Periodicals Inc. [ABSTRACT FROM AUTHOR]

Rating scales, such as Likert scales, are incredibly flexible and intuitive tools for measuring individuals' rating of agreement with or relative preference for many types of stimuli. For humans, this typically involves ratings of agreement between end points representing distinct attitudes or beliefs; For example, strongly disagree to strongly agree. Nonverbal versions of Likert scales have also been presented to children, allowing them to indicate their degree of preference, pain, or happiness. However, before the current study, no known efforts had been made to develop a nonverbal rating scale for use with nonhuman animals. Such a scale would be a useful welfare tool, allowing nonverbal individuals to indicate not just relative preferences between pairs of items but their degree of liking for individual items. I present an outline of the steps taken to create such a scale for use with three zoo-housed gorillas. Two gorillas succeeded in associating preferred and less preferred foods with different response buttons but none of the gorillas were able to effectively use the neutral response button. It is possible that limits in gorillas' capacity for conditional discriminations and/or conceptualization of constructs as abstract as "liking" impeded training. These data are relevant for understanding gorilla cognition and can inform continued efforts to create a tool for nonhumans to communicate their preferences to human caregivers in a more nuanced way than is currently possible., (© 2022 Wiley Periodicals LLC.)

ABSTRACT Differences in how the hands of gorillas and chimpanzees contact the ground while knuckle walking have been noted but generally not quantified. It is widely believed that gorillas maintain a pronated arm and contact the ground with digits 2-5 consistently, while chimpanzees have variable arm position and digit contact. To further test these generalizations, distribution of pressure across the manus, peak digital pressures, and hand position were quantified using a pressure mat in eight captive chimpanzees ( Pan troglodytes) and seven gorillas ( Gorilla gorilla). Chimpanzees and gorillas make initial ground contact with the ulnar aspect of the hand and pressure moves radially. They differ in which digit usually makes final contact and receives maximum pressure, and hand position during contact. Gorillas regularly use a palm-back hand position and touch-off with digit 2. They show less variation in pressure application across the digits. Chimpanzees are more variable in hand position and pressure application. In both, hand position plays a key role in determining which digit acts as the final touch-off element. Am J Phys Anthropol 152:44-50, 2013. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Aim To predict the distribution of suitable environmental conditions ( SEC) for eight African great ape taxa for a first time period, the 1990s and then project it to a second time period, the 2000s; to assess the relative importance of factors influencing SEC distribution and to estimate rates of SEC loss, isolation and fragmentation over the last two decades. Location Twenty-two African great ape range countries. Methods We extracted 15,051 presence localities collected between 1995 and 2010 from 68 different areas surveyed across the African ape range. We combined a maximum entropy algorithm and logistic regression to relate ape presence information to environmental and human impact variables from the 1990s with a resolution of 5 × 5 km across the entire ape range. We then made SEC projections for the 2000s using updated human impact variables. Results Total SEC area was approximately 2,015,480 and 1,807,653 km2 in the 1990s and 2000s, respectively. Loss of predicted SEC appeared highest for Cross River gorillas (−59%), followed by eastern gorillas (−52%), western gorillas (−32%), bonobos (−29%), central chimpanzees (−17%) and western chimpanzees (−11%). SEC for Nigeria- Cameroon chimpanzees and eastern chimpanzees was not greatly reduced. Except for Cross River and eastern gorillas, the number of SEC patches did not change significantly, suggesting that SEC loss was caused mainly by patch size reduction. Main conclusions The first continent-wide perspective of African ape SEC distribution shows dramatic declines in recent years. The model has clear limitations for use at small geographic scales, given the quality of available data and the coarse resolution of predictions. However, at the large scale it has potential for informing international policymaking, mitigation of resource extraction and infrastructure development, as well as for spatial prioritization of conservation effort and evaluating conservation effectiveness. [ABSTRACT FROM AUTHOR]

Purpose To describe the pre-surgical, surgical, and post-surgical considerations for phacoemulsification in non-human primates. Methods Records of non-human primates that underwent phacoemulsification by the Ophthalmology Services of FHCV- UAB and HCV- UM, between 2003 and 2009 were reviewed. Results Five primates were represented: one gorilla, one chimpanzee, one pygmy marmoset, one orangutan, and one chacma baboon. Three were males and two females, of a median age of 16.8 years. Four primates presented bilateral cataracts and one unilateral (n = 9 eyes). Cataracts were immature in two eyes, mature in four and hypermature in 3. One-handed phacoemulsification was used in seven eyes and a two-handed technique in 2. Intraocular lenses ( IOLs), with optic powers between +19.0 and +21.5D, were implanted in the four large-sized primates. All the primates were more active and social after the surgery. Conclusion Phacoemulsification in non-human primates is highly successful and associated with an overall good visual outcome. Nevertheless, specific considerations should be applied in these species. [ABSTRACT FROM AUTHOR]

Infant-directed speech is a linguistic phenomenon in which adults adapt their language when addressing infants in order to provide them with more salient linguistic information and aid them in language acquisition. Adult-directed language differs from infant-directed language in various aspects, including speech acoustics, syntax, and semantics. The existence of a 'gestural motherese' in interaction with infants, demonstrates that not only spoken language but also nonvocal modes of communication can become adapted when infants are recipients. Rhesus macaques are so far the only nonhuman primates where a similar phenomenon to 'motherese' has been discovered: the acoustic spectrum of a particular vocalization of adult females may be altered when the addressees are infants. The present paper describes how gorillas adjust their communicative strategies when directing intentional, nonvocal play signals at infants in the sense of a 'nonvocal motherese.' Animals of ages above infancy use a higher rate of repetitions and sequences of the tactile sensory modality when negotiating play with infants. This indicates that gorillas employ a strategy of infant-specific communication. Am. J. Primatol. 74:841-852, 2012. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Three feeding enrichment treatments were tested in an outdoor yard used by six Western lowland gorillas ( Gorilla gorilla gorilla). In 'Yard-toss,' forage was thrown by hand over one third of the yard. In 'Set-up,' forage and browse were hand-scattered throughout the yard. 'Set-up Enriched' was similar with the addition of either a hay- and forage-filled feeder or forage-filled boomer ball(s) suspended from a climbing structure. Each treatment was presented on 5 d. Behavior was recorded for 30 min before (baseline) and 30 min after the start of each treatment. All treatments led to more foraging and less inactivity compared with baseline ( P80.05), but Yard-toss was the least effective, likely because resources were clumped and monopolized by dominant animals. In Set-up Enriched, dominant animals had the greatest increase in foraging ( P=0.03), partly because they generally monopolized the suspended items, but this allowed others to forage at ground level. This separation of the animals likely explains why Set-Up Enriched led to more foraging than all other treatments ( P80.05). Findings show that for these hierarchical animals, enrichment resources are most effective when distributed widely, including vertically, and that enrichment strategies must take social structure into account. Zoo Biol 31: 235-241, 2012. © 2011 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

While all great apes have been documented to use tools, gorillas are arguably the least proficient tool users. In 2009, a Western lowland gorilla ( Gorilla gorilla gorilla) at the Buffalo Zoo was observed using a bucket, which had been provided as part of normal enrichment, as a tool to collect water. We conducted a brief, ad libitum investigation to confirm the validity of the initial observation. We then carried out a systematic investigation of the behavior in 2010. We collected 72 hr of videotaped data and tested the null hypothesis that the gorillas did not differ in their prevalence of engaging in bucket-use behaviors. We documented that all four adult gorillas in the group used buckets as drinking tools; however, there was significant individual variation in frequency and type of use of buckets. Four of the eight behaviors showed significant variation among individuals. The silverback male and the youngest adult female contacted and held the bucket significantly more than the remaining two adult females. The young female carried and drank from the bucket significantly more than any other individual. Furthermore, she was observed to fill the bucket with water four of the six times during which this behavior was observed. These data provide evidence of the ability of gorillas to utilize tools, given the appropriate environmental conditions. We continue to explore the abilities of gorillas to recognize the functionality of buckets as tools. Zoo Biol 31: 260-266, 2012. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]