Effects of Chromolaena odorata on mammalian biodiversity in Hluhluwe-iMfolozi Park, South Africa

Abstract

This study investigated the effects of the Triffid weed Chromolaena odorata on small and large mammals in Hluhluwe-iMfolozi Park. C. odorata is a widespread invasive alien plant that poses threat to the highly maintained natural vegetation in HiP and most other protected areas in KwaZulu-Natal. Following the opinion that the effects of invasive alien plants on all levels of biodiversity need to be recognised for their effective control, we compared small and large mammal species richness and diversity between areas with differing C. odorata invasion durations, areas with differing clearing times and an area with no history of invasion as a control area. Small mammal trapping was done using Sherman live traps and mark-recapture techniques. Track counts were used to estimate large mammal species abundance, richness and diversity. The control area had higher small mammal species richness and diversity than the invaded areas, which suggests that invaded areas were not suitable habitats for small mammals. It was also found that small and large mammal species richness and diversity decreased with the increase in invasion duration, which shows that the more time C. odorata is left to establish the more disturbance it causes to the habitat. We found the uninvaded treatment to have the highest diversity of large mammal species than all the invaded treatments, which suggests that large mammalian species show some degree of avoidance to the invaded areas. We also found that there were significant differences between the treatments with regard to large mammal species diversity indices. Some of the large mammalian species appeared to neither avoid nor prefer invaded areas. It is hypothesized that they use invaded areas to hide away from predators as most of them fall prey to many carnivores. Also, C. odorata invaded areas could provide suitable shelter from climatic extremes. The treatments cleared of C. odorata showed an increase in both small and large mammalian species richness and diversity, suggesting that clearing of this plant helps in rehabilitation of the ecosystem. However, large mammal species composition in the cleared treatments remained different to preinvasion state, which suggests that the habitat may remain changed for a long time after clearing. Managers of conservation areas should therefore prioritise alien plant removal in order to maintain healthy ecosystems.