Land use affects rodent communities in Kalahari savannah rangelands

Shrub encroachment caused by overgrazing has led to dramatic changes of savannah landscapes and is considered one of the most threatening forms of rangeland degradation leading to habitat fragmentation. Although changes to plant assemblages are becoming better known, however, our understanding of how shrub encroachment affects rodent communities is low. In this study, we investigated relative abundance of five rodent species in sixteen southern Kalahari rangelands where shrub cover ranged from low (< 5%) to high (> 25%). Rodent abundance was determined on three trapping grids (40 x 100 m) for each site. Our results show that increasing shrub cover affected rodent species differently. The relative abundance of hairy-footed gerbil, short-tailed gerbil and bushveld gerbil declined with increasing shrub cover, whereas highveld gerbil and striped mouse exhibited hump-shaped relationships with shrub cover. Overall, species richness decreased with increasing shrub cover and a negative impact of high shrub cover above 15% on rodent abundance was congruent for all species. We conclude that our results support the hypothesis that long-term heavy grazing that results in area wide shrub encroachment, threatens the diversity of arid environments.