Population dynamics and future conservation of a free-ranging black rhinoceros (Diceros bicornis) population in Kenya

The black rhinoceros has declined throughout its range since the 1960s as a result of illegal killing to supply the international trade in rhino horn. However, in recent years the decline has been halted and reversed as a result of the protection and management of rhinos in a small number of key areas. This paper assesses population recovery in one such area, the Masai Mara, since the mid 1980s, using data from daily surveillance patrols. Although a partial recovery to 35 individuals at a growth rate of 9.8% per annum took place until 1994, the population then appeared to decline to 23 individuals by 1999. At no point did the population size or density approach that of the population prior to poaching. The apparent decline could be a result of death, dispersal or an increased reclusiveness amongst some individuals. Evidence suggests that this population extends beyond both protected area and international borders within the Serengeti-Mara ecosystem, and a comparison of the age and sex structure of present versus disappeared rhinos implies that dispersal of sub-adult individuals may partly explain the recent decline. Intensive monitoring with regular assessment of rhino population performance is vital to avoid complacency and identify potential problems quickly. It is recommended that cross-border monitoring is implemented to identify and protect the full range of this population, and to try to ascertain the fate of individuals that have disappeared. (C) 2001 Elsevier Science Ltd. All rights reserved.