Abstract:
Many of the elephant populations in South Africa consist of small reintroduced populations in conservation areas smaller than 1000 km2. In this dissertation I have analysed demographic and genetic factors which may affect extinction risk for these populations. A modelling approach was used to determine the demographic factors that influenced the growth of the Pilanesberg National Park population. Demographic factors that could affect future population growth as well as harvesting, as a management action, were investigated. Previous and future growth rates were found to be higher than the long-term maximum of 7% per annum. Intercalving interval was the most sensitive demographic factor in future projections. Harvesting of adult males was found to be a very effective short-term management option for managing population growth. The stochastic models were found to be more representative of the real situation and are therefore more appropriate for further analyses of small populations. Non-invasive DNA sampling techniques for population genetic studies of free-ranging animals have become increasingly popular, especially over the last 10 years. I conducted a pilot study to critically evaluate previously described faecal storage and faecal DNA extraction methods for efficiency and repeatability under local conditions. The quality and quantity of the faecal DNA obtained was evaluated by polymerase chain reaction (PCR) amplification of mitochondrial DNA (mtDNA) and microsatellite loci. Ideal dung storage and DNA extraction methods were identified. The problem of environmental contamination was highlighted during the amplification of the cytochrome b gene. Amplifications of the same samples three months after initial extractions were unsuccessful. Attempts to amplify DNA using elephant-specific mtDNA primers and microsatellites were unsuccessful. Under current conditions, I showed that obtaining sufficient quantities and quality of DNA from elephant dung was not possible. Small populations are more likely to suffer from genetic problems, such as the loss of genetic diversity and inbreeding. I assessed the microsatellite diversity in four reintroduced elephant populations and compared them to the populations in the Kruger National Park (one of the source populations) and the Addo Elephant National Park (known to have undergone a severe bottleneck). Microsatellite genetic diversity of the reintroduced populations showed similar levels of heterozygosity and greater allelic richness than that of the Kruger population. MtDNA control region diversity within the southern African region was investigated, and was within the range observed in other African elephant populations. MtDNA haplotypes were shared between southern and eastern Africa, but, the two distinct haplogroups found in previous studies could not be identified in our data set. The failure to consider genetic problems in population management was highlighted by the reduced genetic diversity of the Addo population. I provide a list of genetic considerations which should be kept in mind when managing these populations.
