Temporal variation in utilisation distribution and direction distribution of dugong feeding trails in intertidal seagrass beds in Talibong Island, Thailand: an insight into dugong feeding routes

Abstract

Context A better understanding of animal habitat use informs fundamental ecology and can provide underpinnings for effective management. Aims This study explored the temporal variation in feeding ground utilisation by dugongs (Dugong dugon) in two intertidal seagrass beds in Talibong Island, Thailand (Sites A and B), focusing on the distribution and direction of dugong feeding trails. Methods Drone-based aerial photography was conducted quarterly over 1 year and daily over 2 weeks to observe feeding trails and behaviour. Key results During five and seven separate photography periods over 1 year, 0.04 ± 0.01% (range: 0.03–0.06%) of Site A (200,000 m2) was covered with new feeding trails daily, while 0.35 ± 0.31% (range: 0.07–0.96%) of Site B (278,000 m2) was covered daily. This temporal variation in the feeding trail area corresponded to that in seagrass coverage. Daily observations over 2 weeks during six separate photography periods revealed a significant decrease in overlapping rates (intersection over union) of the core areas (50% kernel density estimation [KDE]) as time elapsed. The 1-year observation highlighted relatively higher overlapping rates of home ranges (95% KDE) (Site A: 0.27 ± 0.09; Site B: 0.49 ± 0.08) and low overlapping rates of core areas (Site A: 0.02 ± 0.03; Site B: 0.09 ± 0.09). The relative frequencies of the feeding trail direction remained consistent across survey seasons, and the most and least dominant directions were common across all survey seasons and sites. The circular correlation coefficient between the directions of dugong body axis and the estimated tidal current was 0.45, suggesting that feeding generally occurred in the upstream direction. The direction and spatial range of dugong feeding may be affected by temporally consistent factors. One factor that can affect the feeding direction is the tidal current. Conclusions Overall, dugongs may feed and move within seagrass beds in a temporally consistent manner, even when there are shifts in feeding hotspots. Implications This research enhances our understanding of how dugongs utilise their feeding grounds and highlights the importance of not only identifying feeding hotspots but also predicting their feeding routes by considering the direction and distribution of feeding trails.