Passive Acoustic Monitoring Reveals New Insights Into the Acoustic Occurrence and Foraging Activity of Hector's Dolphins in Porpoise Bay, New Zealand

To effectively mitigate disturbances from human activities on vulnerable dolphin populations, it is crucial to understand fine‐scale variation in habitat use. This study investigated the habitat utilisation of a small subpopulation of Hector's dolphins ( Cephalorhynchus hectori ) in Porpoise Bay, New Zealand. Passive acoustic monitoring was conducted from January to August 2020 using two T‐PODs deployed in the inner and middle of the bay. Generalised additive models were used to investigate the influence of time of day, tidal state, season, and site on Hector's dolphin acoustic occurrence (measured as detection‐positive minutes per hour) and foraging activity (measured as foraging click trains per hour) in the bay. Dolphin acoustic occurrence was greatest during daylight hours and around high tide, particularly in the sheltered inner bay. Foraging activity mirrored these patterns and, like acoustic occurrence, showed no significant seasonal difference. Peak foraging activity occurred in the inner bay during the morning and early afternoon, shifting toward the middle of the bay later in the day. These findings expand our understanding of the drivers of Hector's dolphin habitat use and provide new insights for managing stressors to the subpopulation that uses Porpoise Bay.