Aerial survey intensity as a determinant of estimates of African elephant population sizes and trends

Abstract

Population estimates based on strip transect aerial surveys of large herbivores can aid management decisions if estimates are accurate and precise. Because sampling intensities may influence precision, we simulated survey intensities to determine which could yield accurate and precise population estimates and detect population changes for several African elephant (Loxodonta africana) populations. Simulated surveys of hypothetical elephant populations had to cover 5–20% of a study area to yield accurate estimates, but this depended on how density and distribution varied. Precise estimates, however, needed survey intensities greater than 50%. In addition, the detection of typical rates of population change needed greater sampling intensities than those currently used for most elephant surveys. Survey intensity plays an important role in estimating the accuracy and precision of population estimates and the detection of population trends. Population managers should consider existing information on population density, distribution, and survey intensity to design aerial surveys that will yield both accurate and precise estimates.