Monitoring dugong feeding behavior in a tidal flat by visual and acoustic observation

Abstract

Dugongs (Dugong dugon) are herbivorous marine mammals and an endangered species. Unfortunately, the lack of basic research especially on the use of seagrass patches by dugongs prevents us from taking any effective countermeasures for their conservation. In this study, to monitor the feeding behavior of dugongs in the seagrass bed of a tidal flat, we conducted automatic visual observation and passive acoustic observation using a digital camera and automatic underwater sound monitoring systems for Dugong (AUSOMS-D). These observation methods were tested around Talibong Island, Trang Province, Thailand. The increase in the number of dugong feeding trails was observed by the automatic visual observation. Dugong feeding sounds were observed by the passive acoustic observation. In this study, the term of dugongs feeding in this site was identified by automatic visual observation, and in addition, the time of dugongs feeding in this site was identified by the passive acoustic observation. Therefore, we propose to combine these two observations. The visual-acoustic combined observation method is effective in monitoring feeding behavior of dugongs. This method has technical benefits with no impact on either the dugongs or the seagrass beds.