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Behavioral Ecology and Sociobiology

, Volume 61, Issue 6, pp 919–931 | Cite as

Socioecological influences on the reproductive success of female mountain gorillas (Gorilla beringei beringei)

  • Martha M. Robbins
  • Andrew M. Robbins
  • Netzin Gerald-Steklis
  • H. Dieter Steklis
Original Paper

Abstract

Over the past few decades, socioecological models have been developed to explain the relationships between the ecological conditions, social systems, and reproductive success of primates. Feeding competition, predation pressures, and risk of infanticide are predicted to influence how female reproductive success (FRS) depends upon their dominance rank, group size, and mate choices. This paper examines how those factors affected the reproductive success of female mountain gorillas (Gorilla beringei beringei) of the Virunga Volcanoes, Rwanda from 1967–2004. Reproductive success was measured through analyses of interbirth intervals, infant survival, and surviving infant birth rates using data from 214 infants born to 67 females. Mountain gorillas were predicted to have “within-group scramble” feeding competition, but we found no evidence of lower FRS in larger groups, even as those groups became two to five times larger than the population average. The gorillas are considered to have negligible “within-group contest” competition, yet higher ranked mothers had shorter interbirth intervals. Infant survival was higher in multimale groups, which was expected because infanticide occurs when the male dies in a one-male group. The combination of those results led to higher surviving birth rates for higher ranking females in multimale groups. Overall, however, the socioecological factors accounted for a relatively small portion of the variance in FRS, as expected for a species that feeds on abundant, evenly distributed foliage.

Keywords

Mountain gorilla Female reproductive success Dominance rank Group size Feeding competition Socioecological model 

Notes

Acknowledgment

We appreciate the long-term commitment of Rwanda National Office of Tourism (ORTPN) for supporting the research activities at the Karisoke Research Center. We are greatly indebted to the many researchers and field assistants, who are too numerous to mention here, for the contributions to the long-term demographic and behavioral databases of Karisoke. We thank Maryke Gray, the International Gorilla Conservation Program, and the Ranger Based Monitoring program for the use of the demographic data from the Susa Group. We thank Daniel Stahl for statistical advice and suggestions to improve the manuscript. We also thank Christophe Boesch, Oliver Schülke, Tara Stoinski, and David Watts for comments. We thank the various public and private agencies, foundations, and individuals that have provided support for the Karisoke Research Center over the last four decades. Max Planck Society provided support for data analysis and write up of the project.

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Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  • Martha M. Robbins
    • 1
  • Andrew M. Robbins
    • 1
  • Netzin Gerald-Steklis
    • 2
  • H. Dieter Steklis
    • 2
  1. 1.Max Planck Institute for Evolutionary AnthropologyLeipzigGermany
  2. 2.Dian Fossey Gorilla Fund InternationalAtlantaUSA

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