Abstract:
To determine the vulnerability of black rhinoceros populations in South Africa it was necessary to study all aspects of population biology. Since most of the remaining black rhinoceros populations are small the emphasis was on the genetics and demography of these populations. The aim was to identify those factors that have a negative effect on the effective population size. Thirty protein and enzyme loci of four black rhinoceros populations were studied using starch and polyacrylamide gel electrophoresis. All four populations still carry high levels of genetic variation which is reassuring for the long-term survival of the species. A genetic polymorphism of the erythrocyte enzyme glucose-6-phosphate dehydrogenase was observed. Evidence suggest that a deficiency of this enzyme is associated with intravascular haemolysis similar to the situation in humans. Since haemolytic anaemia is the major cause of rhinoceros mortality in captivity, stress and the administration of some drugs, may induce haemolytic anaemia in G-6-PD deficient rhinoceroses. A demographic extinction model (DEMM) was developed to project the persistence time of South African black rhinoceros populations. The model uses a Leslie matrix with age-specific fecundity and mortality data and was written in Pascal. Other extinction models (Vortex and Goodman) based on the small population paradigm were also used to project the persistence time of different black rhinoceros populations and the results compared to that of DEMM. A population persistence analysis model (PPA) which is based on the declining population paradigm was used to predict persistence time for black rhinoceros populations. PPA is useful in identifying the first stages of a population decline and because the model uses census data (which is easy obtainable), the model is accessible to managers. Poaching, haemolytic anaemia and captive breeding are a few of the problematic issues that emerged from this project and valuable management recommendations are made regarding these.
