Spatial variation of vocalising dugongs around Talibong Island, Thailand

While the occurrence of Dugong (Dugong dugon) has been examined by visual surveys, their habitat use is still not fully understood, since the continuous observation of their behaviour is challenging. Passive acoustic monitoring enables the observation of dugongs’ vocal behaviour, which is one of the key components of their social behaviour, but the temporal and spatial scale of previous studies were limited. In this study, we aimed to examine where dugongs actively vocalised, using multiple underwater recorders that were deployed along the coastline of Talibong Island, Thailand, through one-month observation in both rainy and dry seasons. Dugong calls were automatically detected and false detections were subsequently removed by manual scrutiny. Observations of 1,933 and 2,719 hours were obtained for each season, with a total of 21,340 and 16,337 detected calls, respectively. We found that an elevated rate of detected calls was consistently observed at a few certain monitoring locations in both seasons. These locations should be paid attention in the process of marine spatial planning for their conservation, in addition to the examination of their distribution by visual observation.