Robbins A.M., Gray M., Basabose A., Uwingeli P., Mburanumwe I., Kagoda E., Robbins M.M.
Department of Primatology, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany; International Gorilla Conservation Programme, Kigali, Kigali Province, Rwanda; Parc National des Volcans, Rwanda Development Board, Kigali, Kigali Province, Rwanda; Parc National des Virunga-sud, Institut Congolais Pour la Conservation de la Nature, C/o International Gorilla Conservation Programme, Gisenyi, Western Province, Rwanda; Bwindi Mgahinga Conservation Area, Uganda Wildlife Authority, Kampala, Kampala District, Uganda
Robbins, A.M., Department of Primatology, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany; Gray, M., International Gorilla Conservation Programme, Kigali, Kigali Province, Rwanda; Basabose, A., International Gorilla Conservation Programme, Kigali, Kigali Province, Rwanda; Uwingeli, P., Parc National des Volcans, Rwanda Development Board, Kigali, Kigali Province, Rwanda; Mburanumwe, I., Parc National des Virunga-sud, Institut Congolais Pour la Conservation de la Nature, C/o International Gorilla Conservation Programme, Gisenyi, Western Province, Rwanda; Kagoda, E., Bwindi Mgahinga Conservation Area, Uganda Wildlife Authority, Kampala, Kampala District, Uganda; Robbins, M.M., Department of Primatology, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
Infanticide can be a major influence upon the social structure of species in which females maintain long-term associations with males. Previous studies have suggested that female mountain gorillas benefit from residing in multimale groups because infanticide occurs when one-male groups disintegrate after the dominant male dies. Here we measure the impact of infanticide on the reproductive success of female mountain gorillas, and we examine whether their dispersal patterns reflect a strategy to avoid infanticide. Using more than 40 years of data from up to 70% of the entire population, we found that only 1.7% of the infants that were born in the study had died from infanticide during group disintegrations. The rarity of such infanticide mainly reflects a low mortality rate of dominant males in one-male groups, and it does not dispel previous observations that infanticide occurs during group disintegrations. After including infanticide from causes other than group disintegrations, infanticide victims represented up to 5.5% of the offspring born during the study, and they accounted for up to 21% of infant mortality. The overall rates of infanticide were 2-3 times higher in one-male groups than multimale groups, but those differences were not statistically significant. Infant mortality, the length of interbirth intervals, and the age of first reproduction were not significantly different between one-male versus multimale groups, so we found no significant fitness benefits for females to prefer multimale groups. In addition, we found limited evidence that female dispersal patterns reflect a preference for multimale groups. If the strength of selection is modest for females to avoid group disintegrations, than any preference for multimale groups may be slow to evolve. Alternatively, variability in male strength might give some one-male groups a lower infanticide risk than some multimale groups, which could explain why both types of groups remain common. © 2013 Robbins et al.
age; article; birth; controlled study; female; gorilla; human; infant; infant mortality; infanticide; low risk population; male; population dispersal; population research; progeny; reproductive success; sex difference; social structure; statistical significance; Animal Distribution; Animals; Animals, Newborn; Behavior, Animal; Biological Evolution; Environment; Female; Gorilla gorilla; Male; Population Dynamics; Reproduction; Sex Factors; Social Behavior
