Journal of Tropical Ecology



Vegetation structure and ungulate abundance over a period of increasing elephant abundance in Hwange National Park, Zimbabwe


Marion Valeix a1a2c1, Hervé Fritz a1, Ségolène Dubois a2, Kwanele Kanengoni a3, Samuel Alleaume a4 and Sonia Saïd a5
a1 Centre d'Etudes Biologiques de Chizé, CNRS UPR 1934, 79360 Beauvoir-sur-Niort, France
a2 Integrated Wildlife Management Research Unit, CIRAD EMVT, Campus International de Baillarguet, 34398 Montpellier cedex 5, France
a3 Zimbabwe Parks and Wildlife Management Authority, PO Box CY 140 Causeway, Harare, Zimbabwe
a4 Centre de Recherche pour l'Ingénierie de l'Agriculture et de l'Environnement, 3275 Route de Cézanne, Aix-en-Provence, France
a5 CNERA Cervidés Sanglier, Office National de la Chasse et de la Faune Sauvage, 1 Place Exelmans, 55000 Bar le Duc, France

Article author query
valeix m   [PubMed][Google Scholar] 
fritz h   [PubMed][Google Scholar] 
dubois s   [PubMed][Google Scholar] 
kanengoni k   [PubMed][Google Scholar] 
alleaume s   [PubMed][Google Scholar] 
said s   [PubMed][Google Scholar] 

Abstract

This study investigates whether increases in elephant populations may influence the structure of African savannas, and consequently may affect other herbivores through changes in habitats. Two contrasting periods in terms of elephant population densities were compared in Hwange National Park, Zimbabwe: the early 1980s and the late 1990s. Elephant population density and other ungulate population densities were estimated for a c. 400-km2 area from road counts. Vegetation structure at the landscape scale was assessed using aerial photographs for the same area. All browsers and grazers declined between the early 1980s and the late 1990s, whereas elephants experienced a 16-fold increase. At the landscape scale, vegetation structure changed little with no evidence of an opening of the habitats. These results do not support any kind of medium-term facilitation between elephants and other herbivores. They rather suggest a negative effect of elephants on other herbivore species when elephants are present at high densities. This study rules out a scenario where the decrease of the different herbivore populations was caused by large changes in vegetation structure due to elephant activity.

(Accepted August 11 2006)


Key Words: aerial photographs; Africa; browsers; community; grazers; line transect; megaherbivores; road counts; savanna; transition matrix.

Correspondence:
c1 Corresponding author. Email: mvaleix@yahoo.fr