Advancing crocodiles conservation through aerial ecological monitoring with drones in West Africa

Abstract

Crocodilians play an essential ecological role in West African freshwater ecosystems. However, monitoring them remains difficult due to their secretive behaviour and inaccessible habitats. This study examines the potential of using drones to monitor populations of the species Crocodylus suchus in a sacred pool in northern Benin. During the study, drone flights were conducted at various altitudes (15, 30 and 50 meters), speeds (0 and 2 meters per second) and approach angles (vertical and oblique). Environmental conditions such as land cover, contrast between the animals and the landscape, and observer effort were also assessed. A total of 54 flights were conducted to collect image and video sequences, which were analysed by four trained observers using Timelapse software. Generalised linear mixed models revealed that the probability of detection decreased significantly with altitude and visual contrast, but increased with observation time. Vegetation density had no significant impact on detectability. Interestingly, crocodiles showed no behavioural response to the presence of drones, even at low altitudes, suggesting high tolerance of aerial surveillance. These results highlight the potential of drones as a non-invasive, cost-effective, efficient tool for the ecological monitoring of crocodilians in agro-pastoral landscapes. Our study provides essential information for refining drone survey protocols and proposes a scalable approach to support evidence-based conservation strategies for Crocodylus suchus and similar species in West Africa.