Exploring the influence of management practice on mesopredator and herbivore occupancy and interactions

Ecological studies need to consider ecological interactions between species and their environment across trophic levels. This complexity not only makes the study of ecology very challenging but it also means that ecosystems are vulnerable to change as a disruption at any of the levels could result in cascading effects through the hierarchy. This sensitivity to change makes it especially important to understand ecosystem function as this is needed for effective and adaptive conservation management. A key way in which humans drive and change ecosystem function is through land use and associated management practice. A primary objective of many protected areas is restoration of natural function through re-introduction of large ungulates, which are often fenced and small, thus requiring intensive management that can influence ecosystem function. This is true of the West Coast National Park (the park). Small antelope abundance, and associated drivers, in the contractual Postberg section of the park have been a long-term management question. Postberg is a small (1800 ha) fenced and isolated section of the park which was historically used for agriculture (livestock grazing and some cultivation) and later large wild ungulate species were re-introduced and kept at high densities. The perception of a lower abundance of small antelope has been attributed to predation by a mesopredator (Caracal caracal), however interspecific competition and habitat quality is also known to influence species abundance. Therefore, I aimed to explore the potential mechanisms of small antelope occurrence in the region and how this might differ across three sites with different management practices. Using 18 camera traps, I documented the occurrence of small, medium and large ungulates and caracal. My study spanned across three areas that each represented different forms of management practice with regards to fencing, and stocking rates of managed ungulate species. I made use of single-season, single-species occupancy models in R to assess occupancy of small antelope and caracal and I used the abundance induced heterogeneity model to estimate abundance of managed ungulates. I employed the single-season, two-species occupancy model in PRESENCE to explore species co-occurrence and interactions. Activity patterns and temporal overlap between managed ungulates, small antelope and caracal were assessed using the overlap and activity packages in R. Vegetation height appears to be an important driver of common duiker occupancy. Fallow lands were strongly favoured by managed ungulates suggesting that they may be utilising these patches for foraging. Small antelope occupancy was highest outside of the park and caracal detections were lowest outside of the park. The low detection of caracal across all areas, along with the known diet of caracals, suggests that predation is not likely the driver of small antelope occurrence. Our data suggest that co-occurrence between small antelope and managed ungulates is high and that these sympatric species have probably partitioned food resources. I found that small antelope were mostly crepuscular, managed ungulates more diurnal while caracal were primarily nocturnal. There was a high overlap between small antelope and managed ungulate activity while overlap between caracal and small antelope indicates some temporal partitioning. Overall I found some effects of inter-specific interactions at the local scale. There was, however, no consistent pattern across the areas which, in line with literature, suggests large scale ecological trends are difficult to detect at local scales. Due to the heterogeneity of the region’s vegetation, coupled with the small size of the biome and extensive fragmentation by land use, there are few areas which adequately represent the biome to test how large ungulates would utilise the area at a large scale. This has important implications for the management of small protected areas in the region who are mandated to restore these areas to their historical and natural function. The ability of conservation managers to meet objectives of restoring parks to their historical function, and maintaining these systems as such, may be questioned if our protected areas are not meeting the spatial requirements of re-introduced species