Trade-offs of predation and foraging explain sexual segregation in African buffalo

Authors

  • C. T. Hay,

    1. Department of Nature Conservation, Tshwane University of Technology, Staatsartillerie Road, Private Bag X680, Pretoria West, Pretoria 0001, South Africa;
    2. Mammal Research Institute, University of Pretoria, Lgnnwood Road, Hillcrest, Pretoria 0002, South Africa;
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    • Both authors contributed equally.

  • P. C. Cross,

    Corresponding author
    1. Northern Rocky Mountain Science Center, United States Geological Survey, 229 AJM Johnson Hall, Bozeman, MT 59717, USA; and
    2. Department of Ecology, Montana State University, PO Box 173460, Bozeman, MT 59717–3460
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    • Both authors contributed equally.

  • P. J. Funston

    1. Department of Nature Conservation, Tshwane University of Technology, Staatsartillerie Road, Private Bag X680, Pretoria West, Pretoria 0001, South Africa;
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*Correspondence author. E-mail: pcross@usgs.gov

Summary

  • 1Many studies have investigated why males and females segregate spatially in sexually dimorphic species. These studies have focused primarily on temperate zone ungulates in areas lacking intact predator communities, and few have directly assessed predation rates in different social environments.
  • 2Data on the movement, social affiliation, mortality and foraging of radio-collared African buffalo (Syncerus caffer) were collected from 2001–06 in the Kruger National Park, South Africa.
  • 3The vast majority of mortality events were due to lion (Panthera leo) predation, and the mortality hazard associated with being an adult male buffalo in a male-only ‘bachelor’ group was almost four times higher than for adult females in mixed herds. The mortality rates of adult males and females within mixed herds were not statistically different. Mortality sites of male and female buffalo were in areas of low visibility similar to those used by bachelor groups, while mixed herds tended to use more open habitats.
  • 4Males in bachelor groups ate similar or higher quality food (as indexed by percentage faecal nitrogen), and moved almost a third less distance per day compared with mixed herds. As a result, males in bachelor groups gained more body condition than did males in breeding herds.
  • 5Recent comparative analyses suggest the activity-budget hypothesis as a common underlying cause of social segregation. However, our intensive study, in an area with an intact predator community showed that male and female buffalo segregated by habitat and supported the predation-risk hypothesis. Male African buffalo appear to trade increased predation risk for additional energy gains in bachelor groups, which presumably leads to increased reproductive success.

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