Implementation of the Deer Aerial Abundance Index by Drone with thermal sensor

Abstract

An innovative protocol for monitoring deer abundance using a drone with a thermal sensor was developed and implemented to assess the abundance of deer populations in the project's priority areas. Observations from this first implementation confirmed a high concentration of herds in hard-to-reach areas where hunting for food is virtually non-existent, reaching densities in some places that are certainly a world record - all deer species taken together. To develop this protocol, initial tests were carried out on various habitats (savannah, dry and humid forest) and at different attitudes and slopes, contributing to the formalization of a feasibility study. This led to the development of a method that could be used in areas that are very difficult to access, without the risk of frightening the animals away. This phase also saw the development of an automatic detection and counting algorithm, capable of distinguishing the thermal signature of deer from those of other mammals in optimal conditions. Finally, cartographic analysis and field reconnaissance of priority areas enabled us to define the recommended pilot sites. The implementation of the Aerial Abundance Index by Drone (IAAD), between December 2023 and March 2024, enabled the detection of 2,043 deer over a surveyed area of 4,694 hectares. This result is the fruit of 97 flight plans lasting a total of 118 hours. These enabled the survey of sectors spread across the three priority zones, and were defined to offer a diversity of monitoring conditions, particularly in terms of habitat (forest, savannah, mining scrub) and vegetation strata (herbaceous, shrubby, arboreal). Efforts were nevertheless concentrated on herbaceous savannahs on the periphery of or within the rainforest or adjacent shrublands, excluding as far as possible treed areas unfavourable to aerial detection and to deer during the night feeding period. The results show a very high deer abundance, with an average density of 43.5 deer/km2, although this masks significant disparities. The Boréaré area has by far the highest deer density (92 deer/km2), ahead of Konoyes Shaoué (78 deer/km2) and Bas Nindhia (63 deer/km2).