Abstract:
The multimammate rat, Mastomys natalensis Smith 1834, is a dominant species in agro-ecosystems in
Sub-Saharan Africa, but adapts quickly to changes in non-agricultural landscape, particularly woodlands and
forests. In this study we report on reproduction and population dynamics of M. natalensis in deforested high
elevation localities in the Usambara Mountains, north-east Tanzania. We conducted Capture-Mark-Recapture
studies in 2002-2004, and established that reproduction of M. natalensis takes place in the extended wet season
between February and June, and the population density peaks in June-August. Reproduction cease in July to
January and population density drops from July onwards. Reproduction and population density fluctuations are
linked to the duration and amount of rainfall. In years when rainfall was below average and the wet season was
short, the population density was significantly lower (below 10 animals/ha and 60 animals/ha in 2003 and 2004
respectively, compared to >100 animals/ha in 2002 when rainfall was above the seasonal average) (Fdf 2, 13= 9.092,
p<0.01 for in between years variations and Fdf 12, 15 = 5.389, p<0.01 for effect of cumulative annual rainfall on
population density). These densities were much lower than in the lowland savannah habitats in central and
southwest Tanzania. A comparison between the farmland/fallow mosaic fields and agro-forestry areas showed
higher population densities in the former, which have similarities to the preferred habitats in the lowland savannahs.
The increasing abundance of M. natalensis in the Usambara could have some consequences: M. natalensis is major
pest and is involved in the plague cycle in the western Usambara Mountains. Mastomys natalensis is also a strong
competitor and the impact on endemic rodent species, e.g. Lophuromys flavopunctatus and Praomys delectorum is
unknown.
