Gorilla society: What we know and don't know

Harcourt, Alexander H.; Stewart, Kelly J.

doi:10.1002/evan.20142

Cited by 41 publications

(44 citation statements)

References 81 publications

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“…Further, availability of subordinate males as coalition partners does not occur until natal males mature (Robbins, ; Sicotte, ; Stoinski et al, ; Watts, ). Thus, dispersing males face a long period where they alone must defend their newly‐formed groups in interunit encounters, during which rates of aggression are higher than within groups (Robbins, ) and may lead to injury and infanticide (also see Fossey, ; Harcourt & Stewart, ; Rosenbaum, Vecellio, & Stoinski, ).…”

Section: Discussionmentioning

confidence: 99%

Body growth and life history in wild mountain gorillas (Gorilla beringei beringei) from Volcanoes National Park, Rwanda

Galbany

Abavandimwe

Vakiener

et al. 2017

American J Phys Anthropol

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While comparable data are scarce, our findings provide preliminary support for the prediction that mountain gorillas reach maximum body size at earlier ages compared to more frugivorous western gorillas. Data from other wild populations are needed to better understand comparative great ape development, and investigate links between trajectories of physical, behavioral, and reproductive maturation.

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Section: Discussionmentioning

confidence: 99%

Body growth and life history in wild mountain gorillas (Gorilla beringei beringei) from Volcanoes National Park, Rwanda

Galbany

Abavandimwe

Vakiener

et al. 2017

American J Phys Anthropol

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“…If male tenure length is shorter than a male's age to mature, age-graded groups are unlikely to develop. This scenario could provide an alternative explanation for the lack of multimale (kin) groups in western gorillas compared with mountain gorillas [see alternative explanation in Harcourt & Stewart, 2007].…”

Section: Implications For Life-history Theory Social Organization Anmentioning

confidence: 99%

Physical maturation, life‐history classes and age estimates of free‐ranging western gorillas—insights from Mbeli Bai, Republic of Congo

Breuer

Hockemba

Olejniczak

et al. 2008

American J Primatol

156

138

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Physical maturation and life-history parameters are seen as evolutionary adaptations to different ecological and social conditions. Comparison of life-history patterns of closely related species living in diverse environments helps to evaluate the validity of these assumptions but empirical data are lacking. The two gorilla species exhibit substantial differences in their environment, which allows investigation into the role of increased frugivory in shaping western gorilla life histories. We present behavioral and morphological data on western gorilla physical maturation and life-history parameters from a 12.5-year study at Mbeli Bai, a forest clearing in the Nouabalé-Ndoki National Park in northern Congo. We assign photographs of known individuals to different life-history classes and propose new age boundaries for life-history classes in western gorillas, which can be used and tested at other western gorilla research sites. Our results show that western gorillas are weaned at a later age compared with mountain gorillas and indicate slower physical maturation of immatures. These findings support the risk-aversion hypothesis for more frugivorous species. However, our methods need to be applied and tested with other gorilla populations. The slow life histories of western gorillas could have major consequences for social structure, mortality patterns and population growth rates that will affect recovery from population crashes of this critically endangered species. We emphasize that long-term studies can provide crucial demographic and life-history data that improve our understanding of life-history evolution and adaptation and help to refine conservation strategies.

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“…This is most marked in chimpanzees and bonobos, which show multimale-multifemale mating structures in which females mate with most of the unrelated males in their communities. In gorillas, which show primarily polygynous mating structures in which a single dominant male fathers most of the offspring, females commonly disperse when they mature, whereas males either leave or remain until they have an opportunity to attain dominant status in the group (Harcourt and Stewart 2007). These observations have suggested that male philopatry may be an ancestral feature of African apes and humans (Wrangham 1987).…”

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confidence: 99%

Great ape Y Chromosome and mitochondrial DNA phylogenies reflect subspecies structure and patterns of mating and dispersal

et al. 2016

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The distribution of genetic diversity in great ape species is likely to have been affected by patterns of dispersal and mating. This has previously been investigated by sequencing autosomal and mitochondrial DNA (mtDNA), but large-scale sequence analysis of the male-specific region of the Y Chromosome (MSY) has not yet been undertaken. Here, we use the human MSY reference sequence as a basis for sequence capture and read mapping in 19 great ape males, combining the data with sequences extracted from the published whole genomes of 24 additional males to yield a total sample of 19 chimpanzees, four bonobos, 14 gorillas, and six orangutans, in which interpretable MSY sequence ranges from 2.61 to 3.80 Mb. This analysis reveals thousands of novel MSY variants and defines unbiased phylogenies. We compare these with mtDNA-based trees in the same individuals, estimating time-to-most-recent common ancestor (TMRCA) for key nodes in both cases. The two loci show high topological concordance and are consistent with accepted (sub)species definitions, but time depths differ enormously between loci and (sub)species, likely reflecting different dispersal and mating patterns. Gorillas and chimpanzees/bonobos present generally low and high MSY diversity, respectively, reflecting polygyny versus multimale-multifemale mating. However, particularly marked differences exist among chimpanzee subspecies: The western chimpanzee MSY phylogeny has a TMRCA of only 13.2 (10.8-15.8) thousand years, but that for central chimpanzees exceeds 1 million years. Cross-species comparison within a single MSY phylogeny emphasizes the low human diversity, and reveals speciesspecific branch length variation that may reflect differences in long-term generation times.

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Gorilla society: What we know and don't know

Cited by 41 publications

References 81 publications

Body growth and life history in wild mountain gorillas (Gorilla beringei beringei) from Volcanoes National Park, Rwanda

Body growth and life history in wild mountain gorillas (Gorilla beringei beringei) from Volcanoes National Park, Rwanda

Physical maturation, life‐history classes and age estimates of free‐ranging western gorillas—insights from Mbeli Bai, Republic of Congo

Great ape Y Chromosome and mitochondrial DNA phylogenies reflect subspecies structure and patterns of mating and dispersal

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