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Did the elephant and giraffe mediate change in the prevalence of palatable species in an East African Acacia woodland?

Published online by Cambridge University Press:  08 December 2014

Megan K. L. Strauss  and
Craig Packer
Megan K. L. Strauss*
Affiliation:
Department of Ecology, Evolution and Behavior, University of Minnesota, 100 Ecology Bldg, 1987 Upper Buford Circle, Saint Paul, MN 55108, USA
Craig Packer
Affiliation:
Department of Ecology, Evolution and Behavior, University of Minnesota, 100 Ecology Bldg, 1987 Upper Buford Circle, Saint Paul, MN 55108, USA
*
1Corresponding author. Email: strau102@umn.edu
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Abstract:

We report on a 2009 survey of Acacia woodlands in the Seronera area of central Serengeti, Tanzania, and compare the results to previous surveys from the 1970s–1980s. We document a substantial change in woodland structure and composition. From 1978 to 2009, woody plant density (mean ± SD) declined from 255 ± 35 trees ha−1 to 147 ± 14 trees ha−1. Canopy cover declined from 15.1 ± 1.9% to 5.7 ± 0.6%. Canopy volume declined from 1810 ± 207 m3 ha−1 to 1410 ± 121 m3 ha−1. A 19% increase in the relative canopy volume of Acacia robusta, a species avoided by the giraffe, represents a sharp decline in the quality of the giraffe's food supply, which was last comprehensively assessed in 1978. We examine these changes in the context of Pellew's 1983 woodland dynamics model describing the impacts of elephant, giraffe and fire on an Acacia tortilis tree population and determine that our data are qualitatively consistent with this model. We hypothesize that selective elephant and giraffe browsing has contributed to an increase in the relative dominance of unpalatable species, consistent with Pellew's predictions.

Keywords

AcaciaAfrican elephantgiraffeSerengetivegetation impactsunpalatable species
Type
Research Article
Information
Journal of Tropical Ecology , Volume 31 , Issue 1 , January 2015 , pp. 1 - 12
Copyright
Copyright © Cambridge University Press 2014 

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