Response of Wildlife to Bush Thinning on the North Central Freehold Farmlands of Namibia

Abstract
Agriculture is considered the backbone of the Namibian economy. However, bush encroachment affects approximately 45 million hectares of Namibian farmland and in the absence of appropriate restoration measures, negatively affects local biodiversity and the national economy. Bush thinning operations on three freehold farms were assessed to examine the response of local ungulates (small, medium, large) and predators (meso, large).

Camera traps were used to capture wildlife in bush encroached and previously thinned habitats. We hypothesized that thinning would increase the activity of small, medium, and large ungulates, meso and large predators, and that the magnitude of the increase in activity at thinned sites would differ among animal types. Our results revealed that the expected animal captures were not equal – small, medium, and large ungulates were common, large predators were least common; thinned areas had more expected animal captures and overall animal-treatment interactions were almost significant (p = 0.051). The post-hoc tests of treatment by animal types showed significant differences between treatments for large predators (p = 0.016), with a positive response to the thinning treatment. The response to thinning was also positive for all other animal types, but insignificant.

Our results suggest that activity patterns of large predators could be substantially shifted by thinning operations in the Namibian farmland ecosystem. Consequentially, large predators may impact other animal types severely, especially if thinning is done on a small scale. Thinning at a larger scale might spread the predatory risk over a wider landscape, thus reducing the predatory risk effects. This would provide more options for animals to escape or avoid habitat edges that are highly frequented by predators.

This study demonstrated that bush thinning had overall positive to neutral effects and can be used as a method to restore wildlife habitats. To maintain a sparse vegetation structure and improved carrying capacity in previously restored areas, post-thinning management is required to control the re-established saplings.