Assessing the risks of extinction for local populations of roan antelope Hippotragus equinus

Abstract

We estimated the minimum size of the roan antelope Hippotragus equinus population in the Parc National de l'Akagera in Rwanda to be at least 144 animals, based on a two and a half year study of individually recognized stable social groups. Data from the same study were used to estimate the annual birth rate, and the survival rate of male calves, female calves, adult females and juvenile females; and to identify factors which would result in year-to-year variations in survival. The results of this analysis were incorporated into an age-structured model of the population's dynamics which took account of demographic and environmental stochasticity. This model was then used to determine the viability of the roan population in the park and to identify demographic characteristics whose occurrence could be used to predict when the population was most at risk of extinction. The risk of extinction could be predicted if the number of stable groups within the park was monitored in September of each year. This risk could be greatly reduced if a reciprocal arrangement was established with other protected areas such that the population in the park could be reinforced with new stable groups when the number of stable groups fell below three. However, the risks—particularly of disease transfer—associated with such reinforcement programmes should be clearly recognized.