Home ranges, transboundary movements and harvest of elephants in northern Botswana and factors affecting elephant distribution and abundance in the Lower Kwando River Basin

摘要

With recent estimates in excess of 151,000 elephants in northern Botswana, there is growing concern about the management of this large elephant population. Despite several telemetry studies of elephant movements, there is limited information on the seasonal home ranges and transboundary movements of elephants in northern Botswana. Our home range measures of 19 elephants with satellite collars were highly variable by age, sex, season and availability of water. One of our collared bulls had the largest home range (24,828 km2) recorded for African elephants. Their extensive transboundary movements indicate that the elephants of northern Botswana are part of a larger contiguous elephant population encompassing western Zimbabwe, the Caprivi Strip in Namibia, southeast Angola and southwest Zambia. Elephant populations in the Caprivi Strip, southeast Angola and southwest Zambia have been affected by civil war, poaching, human settlements, landmines, and veterinary fences. Based upon our dry season aerial survey of the Caprivi Strip in November 2005, elephant numbers (5,242) increased by only 15% since 1998. The recent dispersal of elephants into Angola from the Caprivi Strip may account for this small increase. In contrast, our three aerial surveys of Luiana Partial Reserve, Angola indicate that elephant numbers are increasing rapidly and expanding their range in the Reserve, from 329 in January 2004 to 1,827 in November 2005. The end of 25 years of civil conflict in Angola probably provided the requisite security for elephants to return to southeast Angola and southwest Zambia. Our wet season (January 2004) and one of our dry season (August 2004) aerial surveys of elephants in Sioma Ngwezi National Park, Zambia indicate that elephant numbers (1,099 and 899, respectively) were similar to those reported by an aerial survey in 1991. However, our second dry season aerial survey (October 2005) indicated that limited access to water and extensive fires can dramatically decrease elephant numbers in the park (385). Conservation of elephants in the Lower Kwando River Basin can be enhanced by: realigning veterinary fences, de-mining, improved land use management, and development of anti-poaching and community conservation programs.