Characterising resting patterns of mother-calf humpback whale groups in a semi-enclosed embayment along the Australian east coast migration pathway

Abstract Humpback whales undertake extensive annual migrations between high latitude feeding grounds and low-latitude breeding grounds. On the migration back to feeding grounds, mothers and their newborn calves rest in coastal embayments for the energetic benefits provided. Unlike other areas where resting has been documented, Jervis Bay, on Australia’s east coast, is remote from both breeding and feeding grounds, and provides a unique opportunity to compare resting behaviour observed within a semi-enclosed embayment to observations offshore. Land-based, boat-based, and UAV surveys were conducted in Jervis Bay in 2018, 2019, and 2021. We show that (i) a disproportionately high percentage of groups with a calf enter Jervis Bay during the southbound migration, (ii) travelling speeds are significantly slower in the Bay compared to offshore, indicating resting behaviour, and (iii) aerial observations highlight resting and nurturing behaviour. Subsequently, we conclude that Jervis Bay is an important area for resting mother-calf humpback whale groups. With improved understanding of their behaviour and movement in the Bay, there is a need to monitor and manage increased anthropogenic activities during the southern migration season.