Evaluation of low‐cost consumer‐grade UAVs for conducting comprehensive high‐frequency population censuses of hippopotamus populations

Abstract

The hippopotamus Hippopotamus amphibious (hereafter referred to as hippo) is classified as vulnerable according to the IUCN Red data list. They play a significant role in aquatic systems as allochthonous nutrient providers, and as facilitators and competitors in grasslands. Traditional census methodologies for hippo are difficult and costly to repeat. Previous research has been conducted on the use of unmanned aerial systems (UASs) to conduct hippo population estimates; however, findings either needed justification through additional field testing or used high-cost UASs that may be unaffordable for management authorities in developing countries in Africa. Therefore, using a low-cost, consumer-grade, DJI Phantom 3 Advanced multi-rotor unmanned aerial vehicle (UAV), 47 surveys were conducted of the hippo population at Ndumo Game Reserve (NGR), South Africa, between August 2016 and July 2017. In addition, comparisons were drawn between the results of and the logistical requirements and costs of the respective helicopter and UAV surveys conducted on the same day of the same hippo population. The use of a consumer-grade UAV permitted frequent, accurate, and comparatively lowcost surveys to identify temporal changes in the number of hippos present in NGR and at different locations within NGR. Hippos are a data deficient species, particularly in remote developing countries. UAVs surveys of hippo will allow accurate, highly repeatable, and comparatively low-cost data collection for management of hippos and the ecosystems within which they occur.

The direct and indirect effects of damming on the Hippopotamus amphibius population abundance and distribution at Bui National Park, Ghana

“…Observations during the wet season show H. amphibius mostly submerge in pools, therefore reducing visibility and researchers' ability to detect and count them. Several studies have confirmed this observation challenge during H. amphibius census in wet seasons, suggesting higher counts during the dry season than the wet season when water levels are higher (Olivier and Laurie 1974;Martin 2005;Kujirakwinja 2010;Zisadza et al 2010;Lhoest et al 2015;Fritsch and Downs 2020). Counts in the dry season are suggested to produce a reliably valid estimate of the H. amphibius population (Timbuka 2012).…”

“…Ground counts survey techniques (land-and boat-based counts) provide comparatively accurate results to record changes in H. amphibius numbers and distribution. Hippopotamus amphibius census during this study were carried out at different periods of the year to determine the seasonal differences in population sizes (Olivier and Laurie 1974;Martin 2005;Kujirakwinja 2010;Zisadza et al 2010;Timbuka 2012;Lhoest et al 2015;Fritsch and Downs 2020). We followed the ground counts method as described by Kujirakwinja 2010 andMartin 2005 to estimate the number of H. amphibius in the Bui National Park from August 2020 to July 2021.…”

Are hippos Africa's most influential megaherbivore? A review of ecosystem engineering by the semi‐aquatic common hippopotamus

“…Yet, where they still occur, they have large impacts and continue to shape present-day ecosystems. Moreover, 'ghosts' of ecosystem engineers past continue to affect contemporary landscapes and by studying extant engineering species we stand to gain valuable insights into these legacy effects and how they continue to affect current-day ecosystem functioning (Frauendorf et al, 2021;Albertson et al, 2022).…”

Drone Surveys Revealed Bottom-Up, And Not Top-Down, Effects On The Marsh Deer Local Abundance

“…Population-level studies of large herbivores are commonly carried out using aerial surveys with manned aircraft (e.g. Caughley, 1974;Vucetich & Peterson, 2004), which is often nancially prohibitive and can prevent the necessary amount of spatial or temporal replications for accurate and frequent estimates needed for decisions in conservation (Ferreira & Aarde, 2009;Fritsch & Downs, 2020). Recently, drones (Unmanned Aerial Systems or Remotely Piloted Aircraft) have emerged as an accessible, safe, and cost-effective alternative for aerial surveys and have been tested to sample large herbivore populations (e.g.…”