, Volume 72, Issue 1, pp 83–91 | Cite as

Food limitation and demography of a migratory antelope, the white-eared kob

  • J. M. Fryxell
Original Papers


Although it is commonly presumed that many populations of large-herbivores are limited by food availability, supporting evidence is scarce. This hypothesis was investigated in a population of over 800,000 white-eared kob in the Boma National Park region of the southern Sudan. Food availability, body condition, and mortality rates of adults and calves were measured during the dry seasons of 1982 and 1983. Sampled age distributions from both the live population and carcasses were used to calculate age-specific rates of mortality. In 1982, food supplies during the dry season were augmented by substantial rainfall, which produced regrowth of grass in areas that ordinarily had little green forage. As a result, fat reserves declined little, and rates of adult mortality showed no increasing trend. Total adult mortality was 5%. In 1983, there was no rainfall during the dry season and food intake was insufficient to meet the estimated energy requirements of kob. As a result, fat reserves declined and adult mortality rates increased fourfold. Total adult mortality was 10% (equivalent to the recruitment rate of yearling into the population). Calf mortality during the dry season was similar in both years (50%), based on field estimates of mortality rates and calf/female ratios. Lactation throughout the dry season possibly provided a buffer for calves against variations in food availability. The age structure of the live population in 1983 suggests that a drought in 1980 reduced kob numbers by 40%. These results suggest that adult survival is influenced strongly by the availability of food during the dry season. However, the duration of the dry season also plays an important role. During the dry season, declining fat reserves make an increasing proportion of the population vulnerable to mortality. As a result, even moderate droughts may lead to substantial changes in population numbers.

Key words

Kobus Antelope Food-limitation Demography 


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  1. Bayliss P (1985) The population dynamics of red and western grey kangaroos in arid New South Wales, Australia. I. Population trends and rainfall. J Anim Ecol 54:111–25Google Scholar
  2. Berry HH (1981) Abnormal levels of disease and predation as limiting factors for wildebeest in the Etosha National Park. Madoqua 12:242–53Google Scholar
  3. Bobek B (1977) Summer food as the factor limiting roe deer population size. Nature (London) 268:47–9Google Scholar
  4. Buechner HK (1974) Implications of social behavior in the management of Uganda kob. In: Geist V, Walther F (eds) The behaviour of ungulates and its relation to management, Vol. 2, I.U.C.N., Morges, Switzerland, pp 853–70Google Scholar
  5. Caughley G (1966) Mortality patterns in mammals. Ecology 47:906–18Google Scholar
  6. Caughley G (1970) Eruption of ungulate populations with emphasis on Himalayan thar in New Zealand. Ecology 51:53–72Google Scholar
  7. Caughley G (1977) Analysis of vertebrate populations. J Wiley and Sons, New YorkGoogle Scholar
  8. Caughley G, Grigg GC, Caughley J, Hill GJE (1980) Does dingo predation control the densities of kangaroos and emus? Aust Wild Res 7:1–12Google Scholar
  9. Caughley G, Grigg GC, Smith L (1985) The effect of drought on kangaroo populations. J Wildl Manage 49:679–685Google Scholar
  10. Child G (1972) Observations on a wildebeest dieoff in Botswana. Arnoldia 5:1–13Google Scholar
  11. Christian JJ, Flyger V, Davis DE (1960) Factors in the mass mortality of a herd of Sika deer, Cervus nippon. Chesapeake Sci 1:79–95Google Scholar
  12. Clutton-Brock TH, Guiness FE, Albon SD (1982) Red deer: behavior and ecology of two sexes. Edinburgh University Press, EdinburghGoogle Scholar
  13. Coe MJ, Cumming DH, Phillipson J (1976) Biomass and production of large African herbivores in relation to rainfall and primary production. Oecologia (Berlin) 22:341–54Google Scholar
  14. Corfield TF (1973) Elephant mortality in Tsavo National Park, Kenya. East Afr Wildl J 11:339–68Google Scholar
  15. Demment MW, Van Soest PJ (1985) A nutritional explanation for body-size patterns of ruminant and nonruminant herbivores. Am Nat 125:641–72CrossRefGoogle Scholar
  16. Duncan P (1975) Topi and their food supply. Ph.D. dissertation, University of Nairobi, KenyaGoogle Scholar
  17. East R (1984) Rainfall, soil nutrient status and biomass of large African savannah mammals. African Journal of Ecology 22:245–70Google Scholar
  18. Eberhardt LL (1978) Transect methods for population studies. J Wildl Manage 42:1–31Google Scholar
  19. Emlen JT (1971) Population densities of birds derived from transect counts. Auk 88:323–342Google Scholar
  20. Fowler CW (1981) Density dependence as related to life history strategy. Ecology 62:602–10Google Scholar
  21. Fryxell JM (1985) Resource limitation and population ecology of white-eared kob. Ph.D. dissertation, University of British Columbia, CanadaGoogle Scholar
  22. Fryxell JM (1986) Age-specific mortality: an alternative approach. Ecology 67:1687–92Google Scholar
  23. Fryxell JM (1987) Seasonal reproduction of white-eared kob in Boma National Park, Sudan. African Journal of Ecology (in press)Google Scholar
  24. Gasaway WC, Stephenson RO, Davis JL, Shepherd PEK, Burris OE (1983) Interrelationships of wolves, prey, and man in interior Alaska. Wildl Monogr 84:1–50Google Scholar
  25. Geist V (1971) Mountain sheep: a study in behavior and evolution. University of Chicago Press, ChicagoGoogle Scholar
  26. Gross JE (1969) Optimal yield in deer and elk populations. Trans North Am Wildl Conf 34:372–86Google Scholar
  27. Grubb P (1974) Population dynamics of the Soay sheep. In: Jewell PA, Milner C, Boyd JM (eds) Island survivors: the ecology of the Soay sheep of St. Kilda. Athlone Press. Atlantic Highlands, New Jersey, pp 242–72Google Scholar
  28. Hairston NG, Smith FE, Slobodkin LB (1960) Community structure, population control, and competition. Am Nat 94:421–5CrossRefGoogle Scholar
  29. Hanks J (1981) Characterization of population condition. In: Fowler CW, Smith TD (eds) Dynamics of large mammal populations, J Wiley and Sons, New York, pp 47–73Google Scholar
  30. Hillman JC, Hillman AKK (1977) Mortality of wildlife in Nairobi National Park during the drought of 1973–1974. East Afr Wildl J 15:1–18Google Scholar
  31. Houston DB (1982) The northern Yellowstone elk: ecology and management. Macmillan, New YorkGoogle Scholar
  32. Johnson RR, Dehority BA, McClure KE, Parsons JL (1964) A comparison of in vitro fermentation and chemical solubility methods in estimating forage nutritive value. J Anim Sci 23:1124–8Google Scholar
  33. Jolly GM (1969) Sampling methods for aerial census of wildlife populations. East Afr Agric For J 34:46–9Google Scholar
  34. Keep ME (1973) Factors contributing to a population crash in Nduma Game Reserve. The Lammergeyer 19:16–23Google Scholar
  35. Klein DR (1968) The introduction, increase, and crash of reindeer on St. Mathew Island. J Wildl Manage 32:350–367Google Scholar
  36. Leader-Williams N (1980) Population dynamics and mortality of reindeer introduced into South Georgia. J Wildl Manage 44:640–57Google Scholar
  37. Lowe VPW (1969) Population dynamics of the red deer (Cervus elaphus L.) on Rhum. J Anim Ecol 38:425–57Google Scholar
  38. McCullough DR (1979) The George reserve deer herd: population ecology of a K-selected species. University of Michigan Press, Ann ArborGoogle Scholar
  39. Mech LD, Karns PD (1977) Role of the wolf in a deer decline in the Superior National Forest. U.S. Department of Agriculture, Forestry Service Research Paper NC-148. North Central Forestry Experimental Station, St. Paul, MinnesotaGoogle Scholar
  40. Messier F, Crête M (1985) Moose-wolf dynamics and the natural regulation of moose populations. Oecologia (Berlin) 65:503–12PubMedGoogle Scholar
  41. National Research Council (1975) Nutrient requirements of sheep. National Research Council, National Academy of Sciences, Washington, USAGoogle Scholar
  42. Norton-Griffiths M (1978) Counting animals, (Second edition). Handbook no. 1. African Wildlife Leadership Foundation, Nairobi, KenyaGoogle Scholar
  43. Owen-Smith N (1982) Factors influencing the consumption of plant products by large herbivores. In: Huntley BJ, Walker BH (eds) Ecology of tropical savannas. Springer, Berlin Heidelberg New York, pp 359–404Google Scholar
  44. Riney T (1982) Study and management of large mammals. J Wiley and Sons, New YorkGoogle Scholar
  45. Seip D (1983) Foraging ecology and nutrition of Stone's sheep. Ph.D. dissertation. University of British Columbia, CanadaGoogle Scholar
  46. Schoener TW (1982) The controversy over interspecific competition. Am Sci 70:586–95Google Scholar
  47. Sharrow SH, Motazedian (1983) A comparison of three methods for estimating forage disappearance. J Range Mgmt 36:469–471Google Scholar
  48. Sinclair ARE (1975) The resource limitation of trophic levels in tropical grassland ecosystems. J Anim Ecol 44:497–520Google Scholar
  49. Sinclair ARE (1977) The African buffalo. University of Chicago Press, ChicagoGoogle Scholar
  50. Sinclair ARE (1979) The eruption of the ruminants. In: Sinclair ARE, Norton-Griffiths M (eds) Serengeti: dynamics of an ecosystem, University of Chicago Press, Chicago, pp 82–103Google Scholar
  51. Sinclair ARE, Dublin H, Borner M (1985) Population regulation of Serengeti wildebeest: a test of the food hypothesis. Oecologia (Berlin) 65:266–8Google Scholar
  52. Sinclair ARE, Duncan P (1972) Indices of condition in tropical ruminants. East Afr Wildl J 10:143–9Google Scholar
  53. Skogland T (1985) The effects of density-dependent resource limitations on the demography of wild reindeer. J Anim Ecol 54:359–74Google Scholar
  54. Slobodkin LB, Smith FE, Hairston NG (1967) Regulation in terrestrial ecosystems, and the implied balance of nature. Am Nat 101:109–24CrossRefGoogle Scholar
  55. Smuts GL (1978) Interrelations between predators, prey, and their environment. Bioscience 28:316–20Google Scholar
  56. Spinage CA (1976) Incremental cementum lines in the teeth of tropical African mammals. J Zool (London) 178:117–31Google Scholar
  57. Van Valen L (1973) Patterns and the balance of nature. Evolutionary Theory 1:31–49Google Scholar
  58. Western D (1975) Water availability and its influence on the structure and dynamics of a savannah large mammal community. East Afr Wildl J 13:265–86Google Scholar
  59. Woodgerd W (1964) Population dynamics of bighorn sheep on Wildhorse Island. J Wildl Manage 28:381–91Google Scholar

Copyright information

© Springer-Verlag 1987

Authors and Affiliations

  • J. M. Fryxell
    • 1
  1. 1.Department of ZoologyUniversity of British ColumbiaVancouverCanada

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