Population Survey

This dataset comprises aerial sample count data from a survey conducted in the north of Botswana in October 2014. The survey was conducted using a Cessna 206, giving an estimated elephant population of 129 939 based on a coverage of 12.4% of the survey area of 98 425 km². In three strata, Rakops, Kazuma Forest Reserve (FR) and East Gweta, total counts were used, in which all animals are counted on transects spaced 2 km apart. These strata were small and consist of open grasslands, so wildlife was easily visible in 1-km-wide strips on either side of the aircraft. The overall population of elephants in the survey area remained quite stable between 2010 and 2014, with an increase of just 1.2% between surveys or 0.3% per year. It was noted that much of the change in elephant population numbers within the various survey strata may be due to movements by elephants across international borders and district boundaries within Botswana rather than reproduction or mortality. The all-carcass ratio was observed to be 6.9%. The estimated number of recent (MIKE category 1 and 2) carcasses was 123, producing a fresh-carcass ratio of 0.09%. Forty of these strata were previously surveyed by EWB in 2010 (Chase 2011). To increase the coverage of the elephant’s range in northern Botswana, the 2014 survey added nine strata in the southern and western portions of the study area in Ngamiland and in Central district, so that the total survey area was 34% larger in 2014 than in 2010. Much of the added area was south and west of the Southern Buffalo Fence, where low wildlife populations were expected. Compared to the 2010 EWB survey, the 2014 survey covered a larger area with slightly lower overall sampling intensity (12.4% in 2014 vs 14.4% in 2010). The decrease in sampling intensity is largely due to the addition of strata in Ngamiland and Central Districts that were sampled with 4 - 7% coverage. Nonetheless, using data from previous surveys allowed efficient allocation of sampling effort which led to more precise population estimates than in past surveys. The mean %CI for population estimates in the 2014 survey was 28%, versus 31% for the 2010 EWB survey and 32% for the 2012 DWNP survey. Thus, the 2014 survey produced the most precise estimates to date for wildlife populations in northern Botswana.