Behavioral Ecology and Sociobiology

, Volume 54, Issue 4, pp 329–339 | Cite as

Female dispersal and reproductive success in wild western lowland gorillas (Gorilla gorilla gorilla)

  • Emma J Stokes
  • Richard J ParnellEmail author
  • Claudia Olejniczak
Original Article


This paper presents data on the dispersal patterns and reproductive success of western lowland gorilla females from a long-term study at Mbeli Bai in the Nouabalé-Ndoki National Park, Republic of Congo. We find that female natal and secondary transfer is common. Female immigration rates are negatively related to group size, and emigration rates are positively related to group size, with the net result that larger groups are losing females and smaller groups are gaining females. Furthermore, females transferring between known groups show a preference for significantly smaller groups. However, there is no effect of group size on female reproductive success. Male protection and male quality are considered important in determining female transfer decisions. The case for infanticide is argued and females exhibit strategies that appear to minimise the probability of infanticide following the death of the silverback. Exclusively single-male groups and group formation through female acquisition by solitary males may bias female transfer to lone silverbacks and small groups. The effects of group size on female dispersal and reproductive success are not wholly consistent with an argument for increased foraging costs, and group size effects are more parsimoniously explained by demographic factors. Male protection from intra-group aggression is the most likely factor underlying grouping patterns across gorilla taxa, but differences in population structure and male reproductive strategies may account for inter-specific variation. We stress the need for intra-specific comparisons and more complete data sets on western lowland gorilla feeding behaviour.


Western lowland gorilla Female Reproductive success Infanticide 



We acknowledge the Ministère de l'Enseignement Primaire, Secondaire et Supérieur Charge de la Recherche Scientifique in the Republic of Congo for permission to work in Congo and the Ministère de l'Economie Forestière and the Nouabalé-Ndoki Project of the Wildlife Conservation Society for permission to work in the Nouabalé-Ndoki National Park. We further thank the staff of the Wildlife Conservation Society and the Nouabalé-Ndoki Project for logistical and administrative support. We also thank Yako Valentine, David Morgan, Tina Goody, Angela Nowell, Mary Kerr, Aimee Tsama and Taryn Farrelly for assistance with data collection. Financial support was provided by Columbus Zoo, Busch Gardens, Leakey Foundation, Wenner-Gren, Brookfield Zoo, the Zoological Society of Milwaukee, Primate Conservation Inc., the Boise Fund, Lincoln Park Zoo and a Fulbright Fellowship (C.O.). Fiona Maisels and three anonymous reviewers gave helpful comments on earlier drafts of this manuscript.


  1. Altmann S, Altmann J (1977) On the analysis of rates of behaviour. Anim Behav 25:364–372PubMedGoogle Scholar
  2. Barton R, Byrne R, Whiten A (1996) Ecology, feeding competition and social structure in baboons. Behav Ecol Sociobiol 38:321–329CrossRefGoogle Scholar
  3. Bermejo M (1997) Study of western lowland gorillas in the Lossi Forest of North Congo and a pilot gorilla tourism plan. Gorilla Conserv News 11:6–7Google Scholar
  4. Bermejo M (1999) Status and conservation of primates in Odzala National Park, Republic of Congo. Oryx 33:323–331CrossRefGoogle Scholar
  5. Blake S (1994) A pilot study of western lowland gorilla social organization at the Mbeli Bai, Nouabalé-Ndoki National Park, Northern Congo., Nouabale-Ndoki ProjectGoogle Scholar
  6. Boinski S (1999) The social organization of squirrel monkeys: implications for ecological models of social organization. Evol Anthropol 8:101–111CrossRefGoogle Scholar
  7. Boinski S, Mitchell C (1994) Male residence and association patterns in Costa Rican squirrel monkeys (Saimiri oerstedi). Am J Primatol 34:157–169Google Scholar
  8. Byrne R, Whiten A, Henzi S (1990) Social relationships of mountain baboons: leadership and affiliation in a non-female-bonded monkey. Am J Primatol 20:313–329Google Scholar
  9. Caraco T (1979) Time budgeting and group size: a test of theory. Ecology 60:618–627Google Scholar
  10. Cohen J (1971) Casual groups of monkeys and men: stochastic models of elemental social systems. Harvard University Press, Cambridge, Mass.Google Scholar
  11. Doran DM, McNeilage A (1998) Gorilla ecology and behaviour. Evol Anthropol 6:120–131CrossRefGoogle Scholar
  12. Doran DM, McNeilage A (2001) Subspecific variation in gorilla behaviour: the influence of ecological and social factors. In: Robbins MM, Sicotte P, Stewart KJ (eds) Mountain gorillas: three decades of research at Karisoke. Cambridge Studies in Biological and Evolutionary Anthropology 27. Cambridge University Press, CambridgeGoogle Scholar
  13. Dunbar RIM (1988) Primate social systems. Cornell University Press, Ithaca, N.Y.Google Scholar
  14. Fay JM (1997) The ecology, social organization, populations, habitat and history of the western lowland gorilla (Gorilla gorilla gorilla Savage and Wyman 1847). Graduate School of Arts and Sciences, St Louis, Washington UniversityGoogle Scholar
  15. Fossey D (1984) Infanticide in mountain gorillas (Gorilla gorilla beringei) with comparative notes on chimpanzees. In: Hausfater G, SB Hrdy (eds) Infanticide: comparative and evolutionary perspectives. Aldine, New York, pp 217–236Google Scholar
  16. Fossey D, Harcourt AH (1977) Feeding ecology of free-ranging mountain gorillas (Gorilla gorilla beringei). In: Clutton-Brock TH (ed) Primate ecology. Academic, London, pp 415–477Google Scholar
  17. Gerard-Steklis N, Steklis HD (2001) Reproductive benefits for female mountain gorillas in multi-male groups. Am J Primatol 54:60Google Scholar
  18. Goldsmith ML (1996) Ecological influences on the ranging and grouping behavior of western lowland gorillas at Bai Hokou, Central African Republic. Anthropological Sciences. State University of New York at Stony Brook, New York Google Scholar
  19. Harcourt AH (1978) Strategies of emigration and transfer by female primates with special reference to mountain gorillas. Z Tierpsychol 48:401–420PubMedGoogle Scholar
  20. Harcourt AH, Fossey D, Sabater-Pi J (1981) Demography of Gorilla gorilla. J Zool (Lond) 195:215–233Google Scholar
  21. Janson CH, Goldsmith ML (1995) Predicting group size in primates: foraging costs and predation risks. Behav EcolSociobiol 6:326–336Google Scholar
  22. Kappeler P (1999) Primate socioecology: new insights from males. Naturwissenschaften 85:18–29CrossRefGoogle Scholar
  23. Koenig A, Beise J, Chalise M, Ganzhorn J (1998) When females should contest for food: testing hypotheses about resource density, distribution, size and quality with hanuman langurs. Behav Ecol Sociobiol 42:225–237CrossRefGoogle Scholar
  24. Kuroda S, Nishihara T, Suzuki S, Oko R (1996) Sympatric chimpanzees and gorillas in the Ndoki Forest, Congo. In: McGrew W, Marchant L, Nishida T (eds) Great ape societies. Cambridge University Press, Cambridge, pp 71–81Google Scholar
  25. Magliocca F, Querouil S, Gautier-Hion A (1999) Population structure and group composition of western lowland gorillas in North-Western Republic of Congo. Am J Primatol 48:1–14CrossRefPubMedGoogle Scholar
  26. Malenky R, Kuroda S, Vineberg E, Wrangham R (1994) The significance of terrestrial herbaceous foods for bonobos, chimpanzees and gorillas. In: Wrangham R, McGrew W, Waal Fd, Heltne P (eds) Chimpanzee cultures. Harvard University Press, Cambridge, Mass., pp 59–75Google Scholar
  27. Marsh CW (1979) Female transference and mate choice among Tana River red colobus. Nature 281:568–586PubMedGoogle Scholar
  28. Mitani M, Yamagiwa J, Oko RA, Moutsambote JM, Yumoto T, Maruhashi T (1993) Approaches in density estimates and reconstruction of social groups in the Ndoki forest, northern Congo. Tropics 2:219–229Google Scholar
  29. Mitchell C, Boinski S, Schaik C v (1991) Competitive regimes and female bonding in two species of squirrel monkeys (Saimiri oerstedi and S. sciureus). Behav Ecol Sociobiol 28:5–60Google Scholar
  30. Moore J (1984) Female transfer in primates. Int J Primatol 5:537–589Google Scholar
  31. Morell V (1994) Will primate genetics split one gorilla into two? Science 265:1661Google Scholar
  32. Olejniczak C (1994) Report on a pilot study of western lowland gorillas at Mbeli Bai, northern Congo. Gorilla Conserv News 8:9–11Google Scholar
  33. Parnell RJ (2002a) Group size and structure in western lowland gorillas (Gorilla gorilla gorilla) at Mbeli Bai, Republic of Congo. Am J Primatol 56:193–206CrossRefPubMedGoogle Scholar
  34. Parnell RJ (2002b) The social structure and behaviour of western lowland gorillas (Gorilla gorilla gorilla) at Mbeli Bai, Republic of Congo. PhD thesis, Department of Psychology, University of StirlingGoogle Scholar
  35. Pusey AE, Packer C (1987) Dispersal and philopatry. In: Smuts BB, Cheney DL, Seyfarth RM, Wrangham RW, Struhsaker TT (eds) Primate societies. University of Chicago Press, Chicago, pp 250–266Google Scholar
  36. Remis MJ (1993) A preliminary analysis of nesting behaviour of lowland gorillas in the Central African republic: implications for estimates of population density and understanding group dynamics. Tropics 2:245–255Google Scholar
  37. Remis MJ (1997a) Western lowland gorillas (Gorilla gorilla gorilla) as seasonal frugivores: use of variable resources. Am J Primatol 43:87–109CrossRefPubMedGoogle Scholar
  38. Remis MJ (1997b) Ranging and grouping patterns of a western lowland gorilla group at Bai Hokou, Central African Republic. Am J Primatol 43:111–133CrossRefPubMedGoogle Scholar
  39. Robbins M (1995) A demographic analysis of male life history and social structure of mountain gorillas. Behaviour 132:21–47Google Scholar
  40. Robbins M (1999) Male mating patterns in wild multi-male mountain gorilla groups. Anim Behav 57:1013–1020CrossRefPubMedGoogle Scholar
  41. Rogers E, Williamson E (1987) Density of herbaceous plants eaten by gorillas in Gabon: some preliminary data. Biotropica 19:278–281Google Scholar
  42. Ruvolo M, Pan D, Zehr S, Goldberg T, Disotell T, Dornum Mv (1994) Gene trees and hominoid phylogeny. Proc Natl Acad Sci USA 91:8900–8904PubMedGoogle Scholar
  43. Sabater-Pi J (1977) Contribution to the study of the alimentation of lowland gorillas in the natural state in Rio Muni, Republic of Equatorial Guinea (West Africa). Primates 18:183–204Google Scholar
  44. Schaik C van (1983) Why are diurnal primates living in groups? Behaviour 87:120–144Google Scholar
  45. Schaik C van (1989) The ecology of social relationships among female primates. In: Foley V (ed) Comparative socioecology. Blackwell, London, pp 195–218Google Scholar
  46. Schaik C van (1996) Social evolution in primates: the role of ecological factors and male behaviour. Proc Br Acad 99:9–31Google Scholar
  47. Schaik C van, Kappeler K (1997) Infanticide risk and the evolution of male-female association in primates. Proc R Soc Lond 264:1687–1694CrossRefPubMedGoogle Scholar
  48. Schaller G (1963) The mountain gorilla. University of Chicago Press, ChicagoGoogle Scholar
  49. Sicotte P (1993) Inter-group encounters and female transfer in mountian gorillas: influence of group composition on male behavior. Am J Primatol 30:21–36Google Scholar
  50. Sicotte P (2001) Female mate choice in mountain gorillas. In: Robbins MM, Sicotte P, Stewart KJ (eds) Mountain gorillas: three decades of research at Karisoke. Cambridge Studies in Biological and Evolutionary Anthropology 27. Cambridge University Press, CambridgeGoogle Scholar
  51. Smuts B, Cheney D, Seyfarth R, Wrangham R, Struhsaker T (eds) (1987) Primate societies. Chicago University Press, ChicagoGoogle Scholar
  52. Steenbeek R (1999) Tenure related changes in wild Thomas's langurs. I. Between-group interactions. Behaviour 136:595–625CrossRefGoogle Scholar
  53. Steenbeek R, Assink P, Wich S (1999) Tenure related changes in wild Thomas's langurs. II. Loud calls. Behaviour 136:627–650CrossRefGoogle Scholar
  54. Sterck EHM (1997) Determinants of female dispersal in Thomas langurs. Am J Primatol 44:235–54CrossRefGoogle Scholar
  55. Sterck E (1998) Female dispersal, social organization, and infanticide in langurs: are they linked to human disturbance? Am J Primatol 44:235–254Google Scholar
  56. Sterck EHM, Watts DP, van Schaik CP (1997) The evolution of female social relationship in nonhuman primates. Behav Ecol Sociobiol 41:291–309CrossRefGoogle Scholar
  57. Stewart KJ, Harcourt AH (1987) Gorillas: variation in female relationships. In: Smuts BB, Cheney DL, Seyfarth RM, Wrangham RW, Struhsaker TT (eds) Primate societies. University of Chicago Press, Chicago, pp 165–177Google Scholar
  58. Tutin CEG (1996) Ranging and social structure of lowland gorillas in the Lope Reserve, Gabon. In: McGrew WC, Marchant LF, Nishida T (eds) Great ape societies. Cambridge University Press, Cambridge, pp 58–70Google Scholar
  59. Tutin CEG, Fernandez M (1983) Composition of the diet of chimpanzees and comparisons with that of sympatric lowland gorillas in the Lope Reserve, Gabon. Int J Primatol 30:195–211Google Scholar
  60. Tutin CEG, Fernandez M, Rogers ME, Williamson EA (1992) A preliminary analysis of the social structure of lowland gorillas in the Lope Reserve, Gabon. In: Itoigawa N, Sugiyama Y, Sackett GP, Thompson RKR (eds) Topics in primatology, vol 2. Behaviour, ecology and conservation.Tokyo University Press, Tokyo, pp 245–254Google Scholar
  61. Tutin CEG, Parnell R, White LJT, Fernandez M (1995) Nest building by western lowland gorillas in the Lope Reserve, Gabon: environmental influences and implications for censusing. Int J Primatol 16:53–76Google Scholar
  62. Uitenbroek D (1997) SISA binomial. Southampton, D.G. Uitenbroek. 2002Google Scholar
  63. Watts DP (1984) Composition and variability of mountain gorilla diets in the central Virungas. Am J Primatol 7:323–356Google Scholar
  64. Watts DP (1985) Relations between group size and composition and feeding competition in mountain gorilla groups. Anim Behav 33:72–85Google Scholar
  65. Watts DP (1988) Environmental influences on mountain gorilla time budgets. Am J Primatol 15:295–312Google Scholar
  66. Watts DP (1989) Infanticide in mountain gorillas: new cases and a reconsideration of the evidence. Ethology 81:1–18Google Scholar
  67. Watts DP (1990a) Ecology of gorillas and its relation to female transfer in mountain gorillas. Int J Primatol 11:21–45.Google Scholar
  68. Watts DP (1990b) Mountain gorilla life histories, reproductive competition, and sociosexual behaviour and some implications for captive husbandry. Zoo Biol 9:185–200Google Scholar
  69. Watts DP (1991) Strategies of habitat use by mountain gorillas. Folia Primatol 56:1–16PubMedGoogle Scholar
  70. Watts DP (1994) The influence of male mating tactics on habitat use in mountain gorillas (Gorilla gorilla beringei). Primates 35:35–47Google Scholar
  71. Watts DP (1996) Comparative socio-ecology of gorillas. In: McGrew WC, Marchant LF, Nishida T (eds) Great ape societies. Cambridge University Press, Cambridge, pp 16–28Google Scholar
  72. Watts D (2000) Causes and consequences of variation in male mountain gorilla life histories and group membership. In: Kappeler P (ed) Primate males.Cambridge University Press, Cambridge, pp 169–179Google Scholar
  73. Williamson E (1988) Behavioural ecology of western lowland gorillas in Gabon. University of Stirling, StirlingGoogle Scholar
  74. Williamson EA, Tutin CE, Rogers ME, Fernandez M (1990) Composition of the diet of lowland gorillas at Lope in Gabon. Am J Primatol 21:265–277Google Scholar
  75. Wrangham RW (1979) On the evolution of ape social systems. Soc Sci Inf 18:334–368Google Scholar
  76. Wrangham RW (1980) An ecological model of female-bonded primate groups. Behaviour 75:262–300Google Scholar
  77. Yamagiwa J, Kahekwa J (2001) Dispersal patterns, group structure and reproductive parameters of eastern lowland gorillas at Kahuzi in the absence of infanticide. In: Robbins MM, Sicotte P, Stewart KJ (eds) Mountain gorillas: three decades of research at Karisoke. Cambridge Studies in Biological and Evolutionary Anthropology 27.Cambridge University Press, CambridgeGoogle Scholar

Copyright information

© Springer-Verlag 2003

Authors and Affiliations

  • Emma J Stokes
    • 1
  • Richard J Parnell
    • 2
    Email author
  • Claudia Olejniczak
    • 3
  1. 1.Wildlife Conservation SocietyNouabalé-Ndoki ProjectBrazzavilleCongo
  2. 2.Department of PsychologyUniversity of StirlingStirlingUK
  3. 3.Department of AnthropologyWashington UniversitySt. LouisUSA

Personalised recommendations