East Australian humpback whales (E1) migrate through the warm, sheltered and shallow waters of the Gold Coast Bay (GCB) each season. Over a span of six years (2019–2025), diurnal observations were gathered from commercial whale-watching vessels to investigate how calves of the season (COS) utilise this coastal habitat early in their natal migration.
The study specifically examined four aspects: (1) the depth distribution of COS within GCB, (2) the behavioural modes expressed at this site, (3) the influence of social context, such as the presence of an escort or multiple escorts, and (4) the influence of vessel presence as a distinct category. For each sighting, COS were classified into one of several activity modes based on the observed suite of behaviours: travelling, play, swim training with the mother, or resting. These behavioural modes were then related to local bathymetry, group composition, and vessel category (no vessels and mixed vessel types).
COS were most frequently observed in waters approximately 30 metres deep, where swim training and travelling behaviours were predominant. This suggests that Gold Coast Bay is an important site for developing swim performance and strength in the calves' locomotor system. The presence of escorts, particularly multiple escorts, was associated with greater variability in travel directions, consistent with potential avoidance responses. Additionally, vessel presence and vessel count influenced the behavioural modes expressed by the calves.
These findings highlight the multifunctional importance of bays at this latitude as developmental habitats early in the southern migration and provide insight into how escorts and vessels influence key behavioural milestones in humpback whale calves.