Dolphins rely heavily on sound for several biological processes and critical behaviours. Passive acoustic monitoring (PAM) records the soundscape of an environment and can be used to track species distribution through identifying acoustic vocalisations in these recordings.
In Port Phillip Bay (PPB), a PAM array was used to study the critically endangered Burrunan dolphin population. From 2021 to 2023, more than 150,000 5-min audio recordings were collected from nine PAM sites across PPB. The data was processed using autonomous software (PAMGuard) and manually verified.
The study revealed that Burrunan dolphins were present throughout PPB across all seasons, with seasonality demonstrated at some locations. Detections occurring during night hours, when traditional boat-based methods are not possible, comprised 40% of the dataset, greatly expanding our capacity to study this cryptic species. Interestingly, simultaneous detections at multiple PAM sites indicated multiple pods utilising differing areas of PPB regularly and may indicate site fidelity and significance in habitat selection. This study provided, for the first time, a continuous 24-hour assessment of Burrunan dolphin presence, showcasing the importance of PAM for studying elusive cetacean species.