Population fluctuations and community structure of small mammals in a Swaziland grassland over a three-year period

Abstract

Small mammals were live trapped monthly over a three year period in a subtropical grassland in Swaziland. Seven species of small mammals were recorded from the study grid. There were significant seasonal and inter annual differences in rodent numbers, breeding intensity and community structure. Mastomys natalensis was numerically dominant throughout most of the study period, but its numbers fluctuated widely and without a seasonal basis. Numbers of Lemniscomys rosalia and Mus minutoides also fluctuated widely, but both species tended to be more numerous in the dry winter months. A large proportion of the adult M. natalensis, L. rosalia and Steatomys pratensis were reproductively active in the first breeding season of the study, but breeding intensity decreased sharply in the second and third breeding seasons. Species richness and diversity also fluctuated widely  throughout the study. In general, species richness was highest in winter months, while species diversity increased with decrease in numbers of M. natalensis. Fire had a severe impact on the small mammal community; densities of M. natalensis increased  markedly following the fire, while those of other species declined. Total biomass of small mammals increased, but species  diversity and evenness declined as the community became dominated by a single species. Few long term population studies of small mammals have been conducted in southern Africa. In light of the large inter annual variability potentially present in most small mammal communities of southern Africa, such studies are essential.

Key words: Rodentia, Insectivora, reproduction, Africa, ecology, fire.