Large trees, acacia shrubs, and the density of Thallomys nigricauda in the Thornveld savannah of South Africa

We investigated the density of Thallomys nigricauda (acacia rat or black-tailed tree rat) in correlation to habitat characteristics at the Molopo Nature Reserve (S 25°50′; E 22°55′, South Africa). Data on nest trees and vegetation were sampled on 15 study sites along a transect of 25 km. Abundance of acacia rats was estimated using a combined count of nests and scat accumulations. Large live trees of Boscia albitrunca (>5 m) were preferred for nesting. Nests with offspring had significantly more often food plants (Acacia mellifera or A. luederitzii) close to the nest tree than non-reproductive nests or controls. Hierarchical partitioning revealed the density of large B. albitrunca trees and Acacia erioloba of various size classes were positively correlated to the abundance of the acacia rats. The significance of medium sized A. erioloba disappeared when we used only nests as a measure of acacia rat abundance. Density of food plants showed no significant effect on the abundance of acacia rats. Overall our results differ greatly from observations in other areas, where the acacia rat prefers Acacia trees for nesting.