Differences in Vocalisation Patterns of Dugongs Between Fine-Scale Habitats Around Talibong Island, Thailand

Abstract

Examining characteristics of a species’ fine-scale habitat use contributes to effective and practical spatially explicit conservation. Dugongs (Dugong dugon) are endangered herbivorous mammals that use vocalisation for communication. In a small, specific area of Thai waters, classified here as a “vocal hotspot,” vocalisation rates are elevated, implying that in this area acoustic communication plays an important role. We recorded dugong calls in the vocal hotspot and a nearby feeding area. We then compared temporal patterns of vocalisation between the two sites to investigate the degree of variability in vocalisation between fine-scale habitats, which is important for understanding dugong habitat use by passive acoustic monitoring. From the 489 total hours of recording, 6607 and 2032 calls were observed in the vocal hotspot and feeding area, with mean vocalisation rates (calls per hour) 13.5 and 4.2, respectively. Vocalisation rate had distinctive 24-h periodicity in only the vocal hotspot. Environmental factors that correlated with changes in detected vocalisation rate also differed between the two locations. Water level correlated with vocalisation rate in the feeding area; in contrast, current direction correlated with vocalisation rate in the vocal hotspot. In conclusion, the vocalisation pattern for dugongs differed between the two sites, and we suggest that their habitat use varies at fine spatial scales.