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Mountain gorillas (Gorilla beringei beringei) are one of the most critically endangered great apes in the world. The most common cause of mountain gorilla morbidity and mortality is trauma (e.g., injury from conspecifics or snare entrapment). We conducted a retrospective case-control study of free-ranging, human-habituated mountain gorillas to evaluate factors associated with snare entrapment and the results of clinical intervention. Data were collected from clinical records on all clinical intervention cases (n=132) in Volcanoes National Park, Rwanda, conducted between 1995–2015. Wildlife veterinarians treated 37 gorillas entrapped in snares and 95 gorillas for other clinical conditions (including trauma and respiratory illness). Multivariate statistical analyses revealed that young gorillas (<8 yr old) were more likely than older gorillas to become snared; that comorbidities delayed times to intervention (≥3 d); and that severity of wounds at the time of intervention were associated with increased risk of lasting impairment (including loss of limb or limb function, or death) within 1 mo after intervention. Our results may influence decisions for gorilla health monitoring and treatment to most effectively conserve this critically endangered species. [ABSTRACT FROM AUTHOR]

ABSTRACT Objectives Ecological factors have a dramatic effect on tooth wear in primates, although it remains unclear how individual age contributes to functional crown morphology. The aim of this study is to determine how age and individual diet are related to tooth wear in wild mountain gorillas ( Gorilla beringei beringei) from Volcanoes National Park, Rwanda. Material and Methods We calculated the percent of dentine exposure (PDE) for all permanent molars (M1-M3) of known-age mountain gorillas ( N = 23), to test whether PDE varied with age using regression analysis. For each molar position, we also performed stepwise multiple linear regression to test the effects of age and percentage of time spent feeding on different food categories on PDE, for individuals subject to long-term observational studies by the Dian Fossey Gorilla Fund International's Karisoke Research Center. Results PDE increased significantly with age for both sexes in all molars. Moreover, a significant effect of gritty plant root consumption on PDE was found among individuals. Our results support prior reports indicating reduced tooth wear in mountain gorillas compared to western gorillas, and compared to other known-aged samples of primate taxa from forest and savanna habitats. Discussion Our findings corroborate that mountain gorillas present very low molar wear, and support the hypothesis that age and the consumption of particular food types, namely roots, are significant determinants of tooth wear variation in mountain gorillas. Future research should characterize the mineral composition of the soil in the Virunga habitat, to test the hypothesis that the physical and abrasive properties of gritty foods such as roots influence intra- and interspecific patterns of tooth wear. Am J Phys Anthropol 159:457-465, 2016. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

ABSTRACT Gorillas include separate eastern ( Gorilla beringei) and western ( Gorilla gorilla) African species that diverged from each other approximately 2 million years ago. Although anatomical, genetic, behavioral, and socioecological differences have been noted among gorilla populations, little is known about variation in their brain structure. This study examines neuroanatomical variation between gorilla species using structural neuroimaging. Postmortem magnetic resonance images were obtained of brains from 18 captive western lowland gorillas ( Gorilla gorilla gorilla), 15 wild mountain gorillas ( Gorilla beringei beringei), and 3 Grauer's gorillas ( Gorilla beringei graueri) (both wild and captive). Stereologic methods were used to measure volumes of brain structures, including left and right frontal lobe gray and white matter, temporal lobe gray and white matter, parietal and occipital lobes gray and white matter, insular gray matter, hippocampus, striatum, thalamus, each hemisphere and the vermis of the cerebellum, and the external and extreme capsules together with the claustrum. Among the species differences, the volumes of the hippocampus and cerebellum were significantly larger in G. gorilla than G. beringei. These anatomical differences may relate to divergent ecological adaptations of the two species. Specifically, G. gorilla engages in more arboreal locomotion and thus may rely more on cerebellar circuits. In addition, they tend to eat more fruit and have larger home ranges and consequently might depend more on spatial mapping functions of the hippocampus. Am J Phys Anthropol 156:252-262, 2015. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Understanding the life history correlates of ontogenetic differences in hominoid brain growth requires information from multiple species. At present, however, data on how brain size changes over the course of development are only available from chimpanzees and modern humans. In this study, we examined brain growth in wild Virunga mountain gorillas using data derived from necropsy reports ( N = 34) and endocranial volume (EV) measurements ( N = 86). The youngest individual in our sample was a 10-day-old neonatal male with a brain mass of 208 g, representing 42% of the adult male average. Our results demonstrate that Virunga mountain gorillas reach maximum adult-like brain mass by 3-4 years of age; adult-sized EV is reached by the time the first permanent molars emerge. This is in contrast to the pattern observed in chimpanzees, which despite their smaller absolute brain size, reportedly attain adult brain mass approximately 1 year later than Virunga mountain gorillas. Our findings demonstrate that brain growth is completed early in Virunga mountain gorillas compared to other great apes studied thus far, in a manner that appears to be linked with other life history characteristics of this population. Am. J. Primatol. 75:450-463, 2013. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Mountain gorillas are an endangered great ape subspecies and a prominent focus for conservation, yet we know little about their genomic diversity and evolutionary past. We sequenced whole genomes from multiple wild individuals and compared the genomes of all four Gorilla subspecies. We found that the two eastern subspecies have experienced a prolonged population decline over the past 100,000 years, resulting in very low genetic diversity and an increased overall burden of deleterious variation. A further recent decline in the mountain gorilla population has led to extensive inbreeding, such that individuals are typically homozygous at 34% of their sequence, leading to the purging of severely deleterious recessive mutations from the population. We discuss the causes of their decline and the consequences for their future survival. [ABSTRACT FROM AUTHOR]

The microanatomy of enamel and dentine records important information about the rate and duration of tooth development, and the timing of key developmental milestones and stress events occurring during an individual's life. While much attention has focused on relationships between dental development and life history in great apes, opportunities to examine individuals from well-documented wild populations are exceptionally rare. Further, many taxa remain poorly known. We report on a histological examination of dental development in a young juvenile female mountain gorilla from Volcanoes National Park, Rwanda. This individual died an early death; associated records document the last several months of her life. In first and second mandibular permanent molars, we used histological methods to reconstruct cuspal formation times, daily secretion rates, and age at death, providing the first such data for mountain gorillas. Following a blind protocol, we also charted the timing of stress as recorded by accentuated growth increments. Calculated age at death of this individual was 3.10 years, at which time mandibular M1s were partially erupted through the gingiva. From analyses of daily and long-period growth increments, M1 mesiobuccal cusp calcification initiated 87 days before birth and total cuspal formation time was 2.27 years. Periodicity of long period growth increments was 6 days. A prominent stress line was determined to have formed four months before death, corresponding closely in time to a documented poaching event that left this individual orphaned. Subsequent to this, accentuated increments record repeated incidence of stress during a period of documented reintroduction attempts, injury resulting from aggression by other gorillas and a follow-up surgery. Our observations are consistent with accelerated dental development reported previously for a captive juvenile western gorilla (Schwartz et al. 2006), and demonstrate the value of dental histology for revealing aspects of individual life history and stress in wild great apes. [ABSTRACT FROM AUTHOR]