Elephant survival,rainfall and the confounding effects of water provision and fences |
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Authors: | Adrian M Shrader Stuart L Pimm Rudi J van Aarde |
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Institution: | (1) Conservation Ecology Research Unit, Department of Zoology and Entomology, University of Pretoria, Pretoria, 0002, South Africa;(2) Nicholas School of the Environment and Earth Sciences, Duke University, Durham, NC 27708, USA;(3) Present address: School of Biological and Conservation Sciences, University of KwaZulu-Natal, Scottsville, 3209, South Africa |
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Abstract: | Elephant are increasing across some areas of Africa leading to concerns that they may reduce woodlands through their feeding.
Droughts may help limit elephant numbers, but they are generally both episodic and local. To explore more general impacts
of rainfall, we examine how its annual variation influences elephant survival across ten sites. These sites span an almost
coast-to-coast transect of southern Africa that holds the majority of the ~500,000 remaining savanna elephants. Elephants
born in high rainfall years survive better than elephants born in low rainfall years. The relationship is generally weak,
except at the two fenced sites, where rainfall greatly influenced juvenile survival. In these two sites, there are also extensive
networks of artificial water. Rainfall likely affects elephant survival through its influence on food. The provision of artificial
water opens new areas for elephants in the dry season, while fencing restricts their movements in the wet season. We conclude
that the combination of these factors makes elephant survival more susceptible to reductions in rainfall. As a result, elephants
living in enclosed reserves may be the first populations to feel the impacts of global warming which will decrease average
rainfall and increase the frequency of droughts. A way to prevent these elephants from damaging the vegetation within these
enclosed parks is for managers to reduce artificial water sources or, whenever practical, to remove fences. |
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