The impact of silver wattle (Acacia dealbata) on small mammal assemblages in the Sani Pass region of the Drakensberg

Many non-native species have been introduced into South Africa and many of these have become naturalised and invasive. One of these species is the silver wattle (Acacia dealbata). This tree species has invaded many of the biomes in the country including the grassland biome. It is unknown what impact silver wattle has on small mammals and on biodiversity as a whole. The aim of this study was to assess the impact of silver wattle on small mammal assemblages. Four grassland and four silver wattle sites were selected in the Sani Pass region of the Drakensberg and 25 Sherman traps were laid out in each site and baited for six nights. No significant difference was found in the species richness and abundances of small mammals between the grassland and silver wattle sites. There was however, a great amount of variation within the silver wattle sites, with regard to small mammal assemblages and among the structure of the sites. It seems that silver wattle sites that were in an initial stage of invasion was tolerated much more by small mammals than older sites in a more advanced stage of invasion. It is suggested that the initial invasion of silver wattle favours small mammal recruitment, whereas as invasion progresses conditions become less suitable and small mammals disappear.