Drone-based effective counting and ageing of hippopotamus (Hippopotamus amphibius) in the Okavango Delta in Botswana

A drone-based method proved more effective and accurate than traditional land counts for estimating hippopotamus (Hippopotamus amphibius) numbers and age classes in the Okavango Delta, Botswana. Drone surveys at 40 meters altitude yielded counts 10.6% higher than land counts and 17.6% higher than drone counts at greater heights, with early morning being the least effective time due to hippo activity and submersion. While age classification from drones was comparable to land counts, land-based methods slightly outperformed drones in identifying juveniles and subadults, particularly at higher altitudes or during active periods. This low-cost, repeatable approach offers a rigorous alternative for monitoring hippo populations, addressing the challenges posed by their aggressive behavior and amphibious lifestyle.

Inman, V. L., Kingsford, R. T., Chase, M. J., & Leggett, K. E. A. (2019). Drone-based effective counting and ageing of hippopotamus (Hippopotamus amphibius) in the Okavango Delta in Botswana. Plos One, 14(12), e0219652. https://doi.org/10.1371/journal.pone.0219652