Rhino population sizes and trends

Abstract

The IUCN SSC’s African Rhino Specialist Group (AfRSG) has met every two years since 1991, and updates the status of the African rhino at these meetings with data primarily being provided by official range State representatives. The continental statistics on rhino numbers were most recently updated at the 9th meeting of the IUCN SSC AfRSG held in Tanzania from 24-30 May 2008. The latest numbers reflect the best population estimates as of 31 December 2007. Unlike many species, African rhinos are frequently monitored using techniques which provide relatively accurate and precise population estimates. Many rhino populations routinely use ear-notching; which allows the population either to be completely known or accurately estimated using Rhino Bayesian Mark-Recapture analysis, provided a significant proportion of the population are individually identifiable. However in very large populations (>750) or in very large areas (4,000+ km) individual-based monitoring may not be feasible, and then aerial or ground distance-sampling counts (white rhino) or stratified aerial block count methods (black and white rhino) can be employed. The latter methods however are less precise (i.e. have bigger confidence levels around individual estimates) and the use of modeling to smooth estimates over time can help reduce the impact of year to year sampling variation on continental totals. The majority of African rhinos are monitored using a combination of the approaches above allowing the assessment of trends in overall numbers over time. Estimates based on speculation or very old data (speculative guesstimates) are not included in the population totals given in these tables. Only country totals by sub-species are presented here, as individual population details are kept confidential at the request of some countries (although these are provided to the AfRSG by range States). RHINO NOTES