Population dynamics and relocation success of the oribi antelope (Ourebia ourebi) in KwaZulu-Natal, South Africa.

Abstract

In South Africa, oribi (Ourebia ourebi) antelope are listed as vulnerable. The lack of understanding of their population dynamics makes it difficult for oribi conservation. To address these gaps, I used the Oribi Working Groups’ long-term survey database to determine 1) the trends (increasing, decreasing, stable) in oribi populations across KwaZulu-Natal, 2) the spatial distribution of these trends across the province, and 3) the factors influencing these trends. The overall oribi population trend for KwaZulu-Natal was linked with the number of survey returns submitted. This highlights the importance of landowners submitting consistent returns, resulting in more accurate population estimates. The majority of oribi populations across the province had decreasing population trends. I found that initial population size and the amount of suitable habitat available significantly affected oribi population growth rates. These growth rates increased when the availability of suitable habitat increased. In addition, grazing regime influenced growth rates. However, the variance observed was high, signifying that there may be other factors that are also responsible for driving these growth rates. Dog hunting was non-significant, however, because it is illegal, it was difficult to accurately measure its effect on oribi populations and thus should not be dismissed as a potential threat. Relocating oribi has been used as a conservation tool over the past 16 years. However, the success of these relocations has been poorly documented. To address this, I determined 1) the success rate of previous oribi relocations in KwaZulu-Natal, 2) the factors driving the success/failure of the relocations, and 3) whether relocation is a successful tool for the conservation of oribi in South Africa. I found a relocation success rate of only 10% (N = 1). Moreover, I found that following basic relocation criteria (e.g. the removal of threats (such as predators) or long-term post-release monitoring) was important in assuring relocation success. In all instances where relocations failed, key criteria were not considered prior to the relocation. This was in contrast to the one successful relocation, where all the criteria were considered and followed. Similar to my first study, I found that oribi population size, the availability of suitable habitat, and stocking rates of other large herbivores influenced growth rates, and ultimately, relocation success. Moreover, I found a significant interaction between suitable habitat available and stocking rates and their influence on population growth rates. Ultimately, this study highlights key factors that must be considered in any conservation or management decisions for oribi. In addition, prior to a relocation, landowners need to follow the basic criteria for successful relocations.