Dataset Information

Infant survival in western lowland gorillas after voluntary dispersal by pregnant females.

ABSTRACT: In many social species, after the alpha male has been replaced or the group disintegrates, a female's infant is at risk of infanticide by a male. Female gorillas have developed the rare strategy of secondary dispersal in which they transfer between reproductive groups during the limited time period between weaning an infant and conceiving the next one (voluntary dispersal). By doing so they leave a weaker silverback near the end of his tenure and join a stronger silverback at an earlier stage of his own tenure, thereby mitigating the risk of infanticide if the former dies. If females are pregnant or have unweaned offspring when the only male in the group dies, their offspring are vulnerable to infanticide by the new silverback that they join (via involuntary dispersal). In the few known cases of female gorillas transferring when pregnant (mainly after group disintegration), their offspring were killed. We report here on three adult females that transferred voluntarily while pregnant multiple times between two groups yet their offspring were not killed by the new group's silverback. The gorillas were observed from 1995 to 2015 at the Mbeli Bai research site in northern Republic of the Congo. The females gave birth 5-6 months (gestation period 8.5 months) after their last transfer. To our knowledge, these observations are the first to show that wild female western lowland gorillas can transfer voluntarily while pregnant without incurring infanticide by a new silverback. These observations highlight the behavioural plasticity shown by female gorillas in response to sexual coercion by males.

SUBMITTER: Manguette ML

PROVIDER: S-EPMC7599133 | biostudies-literature | 2020 Nov

REPOSITORIES: biostudies-literature

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Infant survival in western lowland gorillas after voluntary dispersal by pregnant females.

Manguette Marie L ML Breuer Thomas T Robeyst Jana J Kandza Vidrige H VH Robbins Martha M MM

Primates; journal of primatology 20200727 6

In many social species, after the alpha male has been replaced or the group disintegrates, a female's infant is at risk of infanticide by a male. Female gorillas have developed the rare strategy of secondary dispersal in which they transfer between reproductive groups during the limited time period between weaning an infant and conceiving the next one (voluntary dispersal). By doing so they leave a weaker silverback near the end of his tenure and join a stronger silverback at an earlier stage of ...[more]

PMID: 32720106

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Project description:The trabecular bone morphology of adult extant primates has been shown to reflect mechanical loading related to locomotion. However, ontogenetic studies of humans and other mammals suggest an adaptive lag between trabecular bone response and current mechanical loading patterns that could result in adult trabecular bone morphology reflecting juvenile behaviours. This study investigates ontogenetic changes in the trabecular bone structure of the third metacarpal of mountain gorillas (Gorilla beringei beringei; n = 26) and western lowland gorillas (Gorilla gorilla gorilla; n = 26) and its relationship to expected changes in locomotor loading patterns. Results show that trabecular bone reflects predicted mechanical loading throughout ontogeny. Bone volume fraction, trabecular thickness and trabecular number are low at birth and increase with age, although degree of anisotropy remains relatively stable throughout ontogeny. A high concentration of bone volume fraction can be observed in the distopalmar region of the third metacarpal epiphysis in early ontogeny, consistent with the high frequency of climbing, suspensory and other grasping behaviours in young gorillas. High trabecular bone concentration increases dorsally in the epiphysis during the juvenile period as terrestrial knuckle-walking becomes the primary form of locomotion. However, fusion of the epiphysis does not take place until 10-11 years of age, and overall trabecular structure does not fully reflect the adult pattern until 12 years of age, indicating a lag between adult-like behaviours and adult-like trabecular morphology. We found minimal differences in trabecular ontogeny between mountain and western lowland gorillas, despite presumed variation in the frequencies of arboreal locomotor behaviours. Altogether, ontogenetic changes in Gorilla metacarpal trabecular structure reflect overall genus-level changes in locomotor behaviours throughout development, but with some ontogenetic lag that should be considered when drawing functional conclusions from bone structure in extant or fossil adolescent specimens.

Dataset Information

Infant survival in western lowland gorillas after voluntary dispersal by pregnant females.

Publications

Infant survival in western lowland gorillas after voluntary dispersal by pregnant females.

Similar Datasets

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