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The costs of drinking: comparative water dependency of sable antelope and zebra

Authors

  • J. W. Cain III,

    1. Centre for African Ecology, School of Animal, Plant & Environmental Sciences, University of the Witwatersrand, WITS, South Africa
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  • N. Owen-Smith,

    1. Centre for African Ecology, School of Animal, Plant & Environmental Sciences, University of the Witwatersrand, WITS, South Africa
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  • V. A. Macandza

    1. Centre for African Ecology, School of Animal, Plant & Environmental Sciences, University of the Witwatersrand, WITS, South Africa
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    • *Current address: Department of Forestry Engineering, Faculty of Agronomy and Forestry Engineering, Eduardo Mondlane University C.P.257, Maputo, Mozambique.


  • Editor: Andrew Kitchener

James W. Cain. Current address: US Geological Survey, New Mexico Cooperative Fish and Wildlife Research Unit, Department of Fish, Wildlife, and Conservation Ecology, New Mexico State University, Box 30003, MSC 4901, Las Cruces, NM 88003, USA. Tel: +1 575 646 3382; Fax: +1 575 646 1281 Email: jwcain@nmsu.edu

Abstract

Resource partitioning among the ungulate species occupying African savanna ecosystems has been well documented in relation to food resources and habitat features, but few studies have addressed how distinctions in surface water dependency contribute to coexistence. During the dry season surface water becomes restricted to a few perennial sources, while the food resources remaining at this time are also most limited in quantity, especially near water where animals congregate to drink. We compared the movement patterns to and from water of sable antelope Hippotragus niger and zebra Equus quagga herds in Kruger National Park (KNP), South Africa. Owing to distinctions in their digestive systems, we expected sable to drink less frequently than zebra, allowing sable to occupy regions further from surface water than zebra. Sable travelled to water at 2–4-day intervals, versus 1–2-day intervals for zebra. However, sable travelled c. 25% greater distances to water due to the location of their late dry season home ranges relative to perennial water sources; zebra home ranges were generally closer to water sources. Travelling 10–15 km to and from water substantially reduced time spent foraging and resting by both species on days when animals drank. Longer intervals between travel to water by the sable antelope herd enabled it to occupy regions of the landscape further from water than those heavily exploited by the more common grazers during the critical dry season months. By avoiding concentrations of other grazers, the sable also probably gained a reduction in predation risk, balancing the substantial costs in terms of time and energy associated with travel to water. Thereby the distinctions in water dependency of this relatively rare grazer facilitated its coexistence alongside more abundant grazers in the KNP.

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