Elephants or Excrement? Comparison of the Power of Two Survey Methods for Elephants in West African Savanna

Statistical power is the key issue when evaluating wildlife trends. Wildlife managers in West Africa lack light aeroplanes and must often estimate wildlife trends on foot, either by counting the animals themselves or by counting their dung. We compared direct ground counts of elephants and dung counts in two consecutive years in Nazinga Game Ranch in southern Burkina Faso, an area of savanna woodland and shrub savanna. Our purpose was to determine which method was most likely to detect a trend in elephant numbers. The direct ground counts each covered 680 km of transect but sightings were too few to give good estimates of elephant numbers. The dung counts each covered 54 km of transect recorded very large numbers of dung-piles and returned estimates with smaller coefficients of variation. Consequently dung counts had greater statistical power for detecting trends. Although dung counts have been mostly applied in forests, they should also be used in open habitats where information on long-term trends is sought.