Oecologia

, Volume 140, Issue 3, pp 523–532

What limits the Serengeti zebra population?

  • Sophie Grange
  • Patrick Duncan
  • Jean-Michel Gaillard
  • Anthony R. E. Sinclair
  • Peter J. P. Gogan
  • Craig Packer
  • Heribert Hofer
  • Marion East
Population Ecology

DOI: 10.1007/s00442-004-1567-6

Cite this article as:
Grange, S., Duncan, P., Gaillard, J. et al. Oecologia (2004) 140: 523. doi:10.1007/s00442-004-1567-6

Abstract

The populations of the ecologically dominant ungulates in the Serengeti ecosystem (zebra, wildebeest and buffalo) have shown markedly different trends since the 1960s: the two ruminants both irrupted after the elimination of rinderpest in 1960, while the zebras have remained stable. The ruminants are resource limited (though parts of the buffalo population have been limited by poaching since the 1980s). The zebras’ resource acquisition tactics should allow them to outcompete the ruminants, but their greater spatial dispersion makes them more available to predators, and it has been suggested that this population is limited by predation. To investigate the mechanisms involved in the population dynamics of Serengeti zebra, we compared population dynamics among the three species using demographic models based on age-class-specific survival and fecundity. The only major difference between zebra and the two ruminants occurred in the first-year survival. We show that wildebeest have a higher reproductive potential than zebra (younger age at first breeding and shorter generation time). Nevertheless, these differences in reproduction cannot account for the observed differences in the population trends between the zebra and the ruminants. On the other hand, among-species differences in first-year survival are great enough to account for the constancy of zebra population size. We conclude that the very low first-year survival of zebra limits this population. We provide new data on predation in the Serengeti and show that, as in other ecosystems, predation rates on zebras are high, so predation could hold the population in a “predator pit”. However, lion and hyena feed principally on adult zebras, and further work is required to discover the process involved in the high mortality of foals.

Keywords

CoexistenceAfrican ungulatesEquidsBovidsPopulation dynamics

Copyright information

© Springer-Verlag 2004

Authors and Affiliations

  • Sophie Grange
    • 1
  • Patrick Duncan
    • 1
  • Jean-Michel Gaillard
    • 2
  • Anthony R. E. Sinclair
    • 3
  • Peter J. P. Gogan
    • 4
  • Craig Packer
    • 5
  • Heribert Hofer
    • 6
  • Marion East
    • 6
  1. 1.Centre d’Etudes Biologiques de ChizéCNRS UPR 1934Beauvoir-sur-NiortFrance
  2. 2.UMR 5558 “Biométrie et Biologie Evolutive”Université Claude Bernard LYON1Villeurbanne CedexFrance
  3. 3.Centre for Biodiversity ResearchUniversity of British ColumbiaVancouverCanada
  4. 4.USGS, Northern Rocky Mountain Science Center, Forestry Sciences LaboratoryMontana State UniversityBozemanUSA
  5. 5.Department of Ecology, Evolution, and BehaviorUniversity of MinnesotaSt. PaulUSA
  6. 6.Institute of Zoo & Wildlife ResearchBerlinGermany