Insights into site fidelity of a low-density dugong population using small-drone imagery and photo-identification

Abstract

The feasibility of using unoccupied aerial vehicles (UAVs, ‘drones’) to collect high-resolution still and video imagery of dugongs (Dugong dugon) for photo-identification (photo-ID) in the Sindalah Archipelago, NEOM (area ~ 84 km2), within the northeast Red Sea, Saudi Arabia, was evaluated during opportunistic marine megafauna searches. Drone searches were conducted whenever possible over one year (January 2024 to January 2025). A total of 48 dugong observations were made during 91 days of drone flights, covering a cumulative distance of 5,962 km of flying. Of these, 35 (72.9%) were repeat sightings (range = 2 to 8 resights) of nine individuals, identified using tail-fluke notches, scars on the dorsum, or both. The time between first and last sightings ranged from 12 days to 10.5 months, with maximum linear distances between all sightings of individuals ranging 0.71 to 5.12 km (mean = 2.4 km; SD = 1.8 km). The ranges of individuals appeared relatively small, suggesting potential site fidelity. To our knowledge, this represents the first drone-based photo-ID study for dugongs using a combination of fluke markings and scarring, and suggests this technique can yield important data for dugong populations, at least over small spatial and temporal scales. Given the relatively small, low-density population of dugongs in the northeast Red Sea, and threats posed by coastal development in the region, a better understanding of spatial and temporal habitat use of individuals is required. This study will support species management decisions, contributing to conservation of dugongs in the region.