Managing small populations in practice: black rhino Diceros bicornis michaeli in the Ngorongoro Crater, Tanzania

Abstract

Black rhino Diceros bicornis michaeli in Ngorongoro Crater, Tanzania were reduced by poaching from c. 110 animals in the mid 1960s to c. 20 by the mid 1970s. Despite little subsequent poaching the rhino population has not increased. This paper builds on a stakeholder workshop held in September 2003 to consider the problems facing these rhino and make recommendations for management. Research and monitoring is required as conservation decisions are, through necessity, being taken based on expert opinion. Genetic constraints may arise in the future given the small population size. We hypothesize, however, that the rhino population is currently limited by ecological factors including: neonatal predation by hyaena Crocuta crocuta, loss of calving refuges because of a reduction in Acacia xanthophloea, competition for browse with elephant Loxodonta africana and buffalo Syncerus caffer, tick-borne disease, and disturbance from tourism. These factors are exacerbated by an institutional philosophy of non-intervention. We suggest using adaptive inference to assess this hypothesis and to provide managers with appropriate information for rhino conservation.