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Primates

, Volume 50, Issue 4, pp 293–303 | Cite as

Infanticide and social flexibility in the genus Gorilla

  • Juichi YamagiwaEmail author
  • John Kahekwa
  • Augustin Kanyunyi Basabose
Review Article Special contributions to commemorate the 60th anniversary of Japanese primatology

Abstract

Based on the cases of infanticide by male mountain gorillas reported from the Virunga volcanic region, the socioecological and life history features of gorillas satisfy the conditions for which infanticide may be expected. However, there are considerable variations in the occurrence of infanticide between habitats. We analyze the recent reports of infanticides that were directly observed or are suspected based on field evidence in two populations of eastern and western lowland gorillas (Kahuzi and Mbeli Bai, respectively) along with previous reports on mountain gorillas, and consider which social features are linked with and which factors influence the occurrence of infanticide in the gorilla populations. All victims were suckling infants and most of them were killed by males who seemed unrelated to them. Dependent infants are most vulnerable to infanticide when the protector male (its putative father in most cases) is absent, and so male protection ability seems to be important in determining female transfer decisions. Two cases observed in Kahuzi suggest that the infanticidal male may discriminate between infants to accept and those to kill according to his previous interactions with their mothers. Mating for a prolonged period prior to parturition is necessary for immigrant females to avoid infanticide by the new male of the group that they join. Infanticide was usually associated with female transfer, and the patterns of female association at transfer may shape variations in social structure between populations. Female mountain gorillas prefer large groups with multiple males and tend to transfer alone in order to seek more protection against infanticide in Virunga. By contrast, female eastern and western lowland gorillas tend to transfer with other females to small groups or solitary males, and maturing silverbacks take females to establish new groups through group fission in Kahuzi and Mbeli Bai. These differences may result in more multi-male and larger groups in the Virungas than in Kahuzi and Mbeli Bai. Rapid changes in density of gorilla social units and their relations following drastic environmental changes caused by recent human disturbances may also increase the probability of infanticide.

Keywords

Gorilla Infanticide Male reproductive tactics Multi-female transfer Social structure Environmental changes 

Notes

Acknowledgments

This study was financed in part by Grants-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science, and Technology, Japan (No. 162550080 and No. 19107007 to J. Yamagiwa), the Global Environmental Research Fund from the Japanese Ministry of the Environment (F-061 to T. Nishida, Japan Monkey Centre), and the Kyoto University Global COE Program “Formation of a Strategic Base for Biodiversity and Evolutionary Research.” It was conducted in cooperation with the Centre de Recherches en Sciences Naturelles, Democratic Republic of Congo. We thank the Institut Congolais pour Conservation de la Nature of the Congolese government for supporting our research project. We are also greatly indebted to all field assistants in Kahuzi-Biega National Park and the people living in the villages next to the parks for their kind support and hospitality throughout the fieldwork.

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Copyright information

© Japan Monkey Centre and Springer 2009

Authors and Affiliations

  • Juichi Yamagiwa
    • 1
    Email author
  • John Kahekwa
    • 2
  • Augustin Kanyunyi Basabose
    • 3
  1. 1.Laboratory of Human Evolution Studies, Graduate School of ScienceKyoto UniversitySakyoJapan
  2. 2.Parc National de Kahuzi-BiegaInstitut Congolais pour Conservation de la NatureBukavuDemocratic Republic of Congo
  3. 3.Centre de Recherche en Sciences Naturelles, LwiroD.S. BukavuDemocratic Republic of Congo

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