Department of Biology, University of Hamburg, 20146 Hamburg, GERMANY.
Worldwide, fencing is increasingly being used as a conservation tool to mitigate human- wildlife conflict. However, knowledge of its effectiveness and its impacts on different trophic levels is still very limited. For this dissertation, the effectiveness of two human- wildlife conflict mitigation game fences in Botswana, their impact on predator avoidance behaviour of herbivores and their impact on grass biomass and its key chemical characteristics in formerly overgrazed areas were studied.
A simple albeit effective method was developed enabling stakeholders to identify categories of species that threaten the integrity of fences by digging holes underneath them. Further, the pressure a fence experiences by hole-digging species and the time frame of necessary maintenance actions can be determined, depending on the species present in a particular area. African lions proved to be very opportunistic and utilized holes of even small species such as honey badgers, in order to leave protected areas. Therefore, it is recommended that the fence line studied in Khutse/Central Kalahari Game Reserve should be maintained on a daily basis. The Makgadikgadi Pans National Park borders one of Botswana’s highest human-wildlife conflict areas. Using a spoor survey method, the effectiveness of the Makgadikgadi game fence in separating humans and wildlife was studied. During the dry season, when there was no surface water available in the Park and the fence prevented access to long stretches of the Boteti River along the National Park boundary, the fence line was under enormous pressure by wildlife, trying to gain access to the river. Livestock moved into the National Park in high numbers during the rainy season, most probably for grazing. Without the implementation of appropriate maintenance, especially during the dry season, the Makgadikgadi game fence cannot be effective in alleviating human-wildlife conflict.
A cost-effective, repeatable and non-invasive spoor method was used to investigate the effects of game fences on predator-prey relationships. A new fence restricted daily herbivore movement, which led to increased localized herbivore densities along the fence, which further attracted lions. Therefore, herbivores were exposed to a potentially increased hunting pressure along the fence. Spatial lion avoidance behaviour by herbivores could neither be detected along a new nor a well-established fence line. Hence, the installation of fences has the potential to have a long-term negative impact on herbivore populations and needs careful consideration especially in small protected areas with small herbivore populations or areas hosting migratory species.
Lastly, the impacts of fencing on grass biomass and its key chemical characteristics were studied in a formerly overgrazed area in Khutse Game Reserve. High levels of grazing by livestock led to higher protein contents, but lower fibre and hemicellulose contents and lower absolute nutrient availability in grasses per unit area. Heavy grazing further had a negative impact on grass biomass, whereas the exclusion of livestock by fencing resulted in a rapid increase of grass biomass, higher fibre and hemicellulose contents and higher absolute nutrient availability after one rainy season. However, in formerly heavily grazed areas there was a high abundance of unpalatable plant species one year after fencing. Therefore, fencing off an overgrazed area had a positive effect on grass biomass, whereas there was no short-term effect on the species composition in formerly overgrazed sites within one year.
The decision whether or not to use fencing as a conservation tool is dependent on many different factors and has to be decided on a case-by-case basis. This dissertation highlights the need to consider whole ecosystems when fencing is deemed the right choice. Appropriate design, alignment and maintenance are the key factors, which will determine whether fencing will be a success or disaster for conservation.