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Effects of annual rainfall and habitat types on the body mass of impala (Aepyceros melampus in the Zambezi valley, Zimbabwe

Bourgarel M., Fritz H., Gaillard J.M., De Garine-Wichatitsky M., Maudet F.. 2002. African Journal of Ecology, 40 (2) : p. 186-193.

DOI: 10.1046/j.1365-2028.2002.00377.x

Body mass is often considered as a good indicator of body condition of individuals in ungulates, hence of their ¿tness, andthus,maybeusedas anindex tomonitor the status of populations subject to harvesting schemes. Here, we report the in¿uence of annual rainfall (a proxy for primary production) and habitat onthe bodymass of impala in a population cropped for meat in a communal area of Zimbabwe.We analyzed the data from 2 contrasted years for rainfall, in two di!erent habitats. In the good year (i.e. high annual rainfall) impala were heavier than in the poor year, and adult females seemed to be less a!ected than males by variation in primary production.We show that adult males were su!ering from a seasonal decrease in body mass, supposedly linked to the rut, particularly in good habitat. Overall, the habitat e!ect appeared to be dominated by the rainfall e!ect, and this may be due to the very high animal densities in the good habitat, i.e. fast resource depletion. Our results also suggest that males (juvenile and adult) are more susceptible to changes in food resource abundance and quality than females, which supports previous studies on sexually dimorphic and polygynous species.

Mots-clés : habitat; pluviomètre; poids corporel; Écologie animale; animal sauvage; zimbabwe; aepyceros motampus; impala

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