Abstract
Understanding the principles that underly primate social evolution depends on integrated analysis of data on behavioral ecology, demography, life history tactics, and social organization. In this paper, data on the behavioral ecology of gorillas are reviewed and comparisons made among the three subspecies. Gorillas are selective feeders; and, their patterns of food choice are consistent with models of feeding by large generalist herbivores. They rely heavily on terrestrial herbaceous vegetation, which provides an abundant supply of densely distributed food. Availability of this food varies little in space and time; and, gorilla foraging activity can maintain its productivity. The level of frugivory and the extent of seasonal variation in diet and habitat use vary among and within populations. Low variability in food distribution patterns makes cooperative defense of foraging areas not worthwhile; but, it also means that ecological costs associated with gregariousness are low. However, demographic and life history data on mountain gorillas show that these costs may be sufficient to reduce female reproductive success as group size increases. Advantages to being with high quality males apparently can outweigh these costs. The implications of these data for the evolution of the mountain gorilla social system, and the possible roles of male protection, predation, and female/female competition in this regard, are discussed.
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Bate-Smith, E. C. (1972). Attractants and repellents in higher animals. In Harborne, J. H. (ed.),Phytochemical Ecology, Academic Press, London, pp. 43–56.
Bradbury, J. W., and Vehrencamp, S. L. (1977). Social organization and foraging in emballonurid bats, II: A model for the determination of group size.Behav. Ecol. Sociobiol. 1: 383–404.
Bullock, S. H. (1981). Dynamics of vegetative shoots of three species ofAfromamum (Zingiberaceae) in Cameroon.Adansonia 2(20): 383–392.
Butynski, T. (1987). The Impenetrable Forest project, Uganda.Gorilla Conservation News 1:5.
Calvert, J. J. (1985). Food selection by western gorillas (G. g. gorilla) in relation to food chemistry.Oecologia (Berlin) 65:236–246.
Caro, T. M. (1976). Observations on the ranging behaviour and daily activity of lone silverback mountain gorillas (Gorilla gorilla beringei)Anim. Behav. 24: 889–897.
Casimir, M. J. (1975). Feeding ecology and nutrition of an eastern gorilla group in the Mt. Kahuzi region (Republique du Zaire).Folia Primatol. 24:290–308.
Casimir, M. J., and Butenandt, E. (1973). Migration and core area shifting in relation to some ecological factors in a mountain gorilla group (G. g. beringei) in the Mt. Kahuzi region (Republique du Zaire).Z. Tierpsychol. 33: 514–522.
Cooper, S. M., and Owen-Smith, N. (1985). Condensed tannins deter feeding by browsing ruminants in a South African savannah.Oecologia (Berlin) 67: 142–146.
Dunbar, R. I. M. (1984).Reproductive Decisions: An Economic Analysis of Gelada Baboon Social Strategies, Princeton, Princeton University Press.
Dunbar, R. I. M. (1988).Primate Social Systems, Columbia University Press, New York.
Fay, M. (1987). Dzanga-Sangha Gorilla Project (Central African Republic).Gorilla Conservation News 1: 3.
Fossey, D. (1974). Observations on the home range of one group of mountain gorillas (Gorilla gorilla beringei).Anim. Behav. 22: 568–581.
Fossey, D. (1984). Infanticide in mountain gorillas (Gorilla gorilla beringei) with comparative notes on chimpanzees. In Hausfater, G., and Hrdy, S. B. (eds.),Infanticide: Comparative and Evolutionary Perspectives, Aldine, New York, pp. 217–235.
Fossey, D., and Harcourt, A. H. (1977). Feeding ecology of free-ranging mountain gorilla (Gorilla gorilla beringei). In Clutton-Brock, T. H. (ed.),Primate Ecology: Studies of Feeding and Ranging Behaviour in Lemurs, Monkeys, and Apes, Academic Press, London, pp. 415–447.
Goodall, A. G. (1977). Feeding and ranging behavior of a mountain gorilla group (Gorilla gorilla beringei) in the Tshiabinda-Kahuzi region (Zaire). In Clutton-Brock, T. H. (ed.),Primate Ecology: Studies of Feeding and Ranging Behaviour in Lemurs, Monkeys, and Apes, Academic Press, London, pp. 449–479.
Harbourne, J. B. (1982).Introduction to Ecological Biochemistry, Academic Press, London.
Harcourt, A. H. (1978). Strategies of emigration and transfer by primates, with particular reference to gorillas.Z. Tierpsychol. 48: 401–420.
Harcourt, A. H. (1979a). Social relationships among adult female mountain gorillas.Anim. Behav. 27: 251–264.
Harcourt, A. H. (1979b). Social relationships between adult male and female mountain gorillas in the wild.Anim. Behav. 27: 325–342.
Harcourt, A. H. (1981). Intermale competition and the reproductive behaviour of the great apes. In Graham, C. E. (ed.),Reproductive Biology of Great Apes, Academic Press, New York, pp. 301–318.
Harcourt, A. H. (1987). Dominance and fertility among female primates.J. Zool., Lond. 213:
Harcourt, A. H., and Harcourt, S. A. (1984). Insectivory by gorillas.Folia primatol. 43: 229–233.
Harcourt, A. H., and Stewart, K. J. (1984). Gorillas' time spent feeding: Aspects of methodology, body size, competition, and diet.Afr. J. Ecol. 22: 207–215.
Harcourt, A. H., and Stewart, K. J. (1987). The influence of help in contests on dominance rank in primates: Hints from gorillas.Anim. Behav. 35: 182–190.
Harcourt, A. H., Fossey, D., Stewart, K. J., and Watts, D. P. (1980). Reproduction of wild gorillas and some comparisons with chimpanzees.J. Reprod. Fertil., Suppl. 28: 59–70.
Harcourt, A. H., Fossey, D., and Sabater Pi, J. (1981). Demography ofGorilla gorilla.J. Zool., Lond. 195: 215–233.
Jones, C., and Sabater Pi, J. (1971). Comparative ecology ofGorilla gorilla (Savage and Wyman) andPan troglodytes (Blumenbach) in Rio Muni, West Africa.Bibliotheca Primatol. 13: 1–96.
Milton, K. (1980).The Foraging Strategy of Howler Monkeys, Columbia University Press, New York.
Milton, K. (1984). The role of food processing factors in primate food choice. In Rodman, P. S., and Cant, J. G. H. (eds.),Adaptations for Foraging in Nonhuman Primates, Columbia University Press, New York, pp. 249–279.
Moore, J. (1984). Female transfer in primates.Int. J. Primatol. 5: 537–590.
Parra, R. (1978). Comparison of foregut and hindgut fermentation in herbivores. In G. G. Montgomery (ed.),The Ecology of Arboreal Folivores, Smithsonian Institution Press, Washington, D.C., pp. 205–230.
Rogers, M. E., and Williamson, E. A. (1987). Density of herbaceous food plants eaten by gorillas in Gabon: Preliminary results.Biotropica 19: 278–281.
Sabater Pi, J. (1977). Contribution to the study of alimentation of lowland gorillas in the natural state in Rio Muni, Republic of Equatorial Guinea (West Africa).Primates 18: 183–204.
van Schaik, C. P. (1983). Why are diurnal primates living in groups?Behaviour 87: 120–144.
van Soest, P. J. (1982).Nutritional Ecology of the Ruminant. O and B Books, Corvallis, Washington.
Schaller, G. S. (1963).The Mountain Gorilla, University of Chicago Press, Chicago.
Stewart, K. J., and Harcourt, A. H. (1987). Gorillas: Variation in female relationships. In Smuts, B. B., Cheney, D. L., Seyfarth, R. M., Wrangham, R. W., and Struhsaker, T. T. (eds.),Primate Societies, University of Chicago Press, Chicago, pp. 155–164.
Tutin, C. E. J., and Fernandez, M. (1983a) Gorillas feeding on termites in Gabon, West Africa.Mammal. 64: 530–531.
Tutin, C. E. J., and Fernandez, M. (1983b). Recensement des Gorilles et des Chimpanzes du Gabon. CIRMF, Franceville, Gabon.
Tutin, C. E. J., and Fernandez, M. (1985). Foods consumed by sympatric populations ofGorilla g. gorilla andPan t. troglodytes in Gabon: Some preliminary data.Int. J. Primatol. 6: 313–336.
Vedder, A. L. (1984). Movement patterns of a group of free-ranging mountain gorillas (Gorilla gorilla beringei) and their relation to food availability.Am. J. Primatol. 7: 73–88.
Waterman, P. G., Choo, G. M., Vedder, A. L., and Watts, D. P. (1983). Digestibility, digestion inhibitors, and nutrients of herbaceous foliage and green stems from an African montane flora and comparison with other flora.Oecologia (Berlin) 47: 244–249.
Watts, D. P. (1983). Foraging Strategy and Socioecology of Mountain Gorillas (Pan gorilla beringei). PhD. Thesis, University of Chicago, Chicago.
Watts, D. P. (1984). Composition and variability of mountain gorilla diets in the central Virungas.Am. J. Primatol. 7: 323–356.
Watts, D. P. (1985). Relations between group size and composition and feeding competition in mountain gorilla groups.Anim. Behav. 33: 72–85.
Watts, D. P. (1987). Effects of mountain gorilla foraging activities on the productivity of their food plant species.Afr. J. Ecol. 25: 155–163.
Watts, D. P. (1988). Environmental influences on mountain gorilla time budgets.Am. J. Primatol. 15: 295–312.
Watts, D. P. (1989a). Ant eating behavior of mountain gorillas.Primates, 30: 121–125.
Watts, D. P. (1989b). Infanticide in mountain gorillas: New cases and a review of the evidence.Ethology, 81: 1–18.
Watts, D. P. (in press). Habitat use strategies of mountain gorillas.Folia primatol.
Watts, D. P., Vedder, A. L., and Waterman, P. G. Nutritional and allelochemical parameters of food selection by the mountain gorilla (Gorilla gorilla beringei). Unpubl. ms.
Westoby, M. (1974). An analysis of diet selection by large generalist herbivores.Am. Nat. 108: 290–304.
Wittenberger, J. (1980). Group size and polygamy in social mammalsAm. Nat. 115: 197–222.
Wrangham, R. W. (1979). On the evolution of ape social systems.Soc. Sci. Information 18: 335–368.
Wrangham, R. W. (1980). An ecological model of female-bonded primate groups.Behaviour 75: 262–300.
Wrangham, R. W. (1982). Mutualism, kinship, and social evolution. In King's College Sociobiology Group (eds.),Current Problems in Sociobiology, Cambridge University Press, Cambridge, pp. 269–289.
Wrangham, R. W. (1986). Ecology and social relationships in two species of chimpanzees. In Rubenstein, D. I., and Wrangham, R. W. (eds.),Ecological Aspects of Social Evolution, Princeton University Press, Princeton, pp. 352–378.
Wrangham, R. W. (1987). Evolution of social structure. In Smuts, B. B., Cheney, D. L., Seyfarth, R. M., Wrangham, R. W., and Struhsaker, T. T. (eds.),Primate Societies University of Chicago Press, Chicago, pp. 282–296.
Yamagiwa, J. (1983). Diachronic changes in two eastern lowland gorilla groups (Gorilla gorilla graueri) in the Mt. Kahuzi region, Zaire.Primates 24: 174–183.
Yamagiwa, J. (1986). Activity pattern and the ranging of a solitary male mountain gorilla (Gorilla gorilla beringei).Primates 27: 273–282.
Zucker, W. V. (1983). Tannins: Does structure determine function? An ecological perspective.Am. Nat. 121: 335–365.
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Watts, D.P. Ecology of gorillas and its relation to female transfer in mountain gorillas. International Journal of Primatology 11, 21–45 (1990). https://doi.org/10.1007/BF02193694
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DOI: https://doi.org/10.1007/BF02193694