Key factors driving the foraging ecology of Oribi : fear, cattle and the quality and quantity of food.

Abstract

Body size and digestive physiology are two factors that influence herbivores foraging behaviour, habitat use and potential to compete with other animals. The aim of this study was to determine how seasonal changes in grass quality, interactions with cattle, and perceived predation risk influenced oribi (Ourebia ourebi) foraging and landscape use. Oribi are one of the smallest pure grazing ruminants. As a result, they should select high quality vegetation. In line with this, I found that throughout the study oribi fed selectively over multiple spatial scales ranging from plant parts to habitats. By focussing on green grass within these different scales, oribi were able to maintain their crude protein intake needed for maintenance. Throughout South Africa, oribi frequently interact with cattle. Due to their differences in body size and nutritional requirements, there should be sufficient resource partitioning to avoid competition. However, I found that the nature of the interspecific interactions (i.e. competition or facilitation) between these species depended on season and cattle stocking rates. During the wet season, cattle facilitated oribi by providing high quality regrowth. However, at high stocking rates, cattle indirectly competed with oribi during the dry season via the impacts of their wet season grazing. Specifically, intense wet season grazing by cattle reduced the availability of high quality grass for oribi in the dry season. This was not the case at low and intermediate stocking rates. Differences in food availability and predation risk across habitats can influence how herbivores utilise landscapes. I found that predation risk greatly affected oribi foraging behaviour, with oribi preferring to feed in safer rather than riskier habitats. However, when food availability increased in these risky habitats, oribi increased their risk-taking behaviour at both small- and large-scales within these risky areas. Ultimately, this suggests that oribi trade-off between predation risk and food

availability. Finally, to link my results to the management and conservation of this vulnerable antelope, I applied the knowledge I gained from the above research to a case study.