Ontogenetic changes in energy expenditure and resting behaviour of humpback whale mother–calf pairs examined using unmanned aerial vehicles

Context Baleen whale calves rapidly increase in size and improve locomotion abilities, while on their low-latitude breeding ground, allowing them to undertake a successful migration high-latitude feeding grounds. Aims We investigated energy expenditure resting behaviour of humpback (Megaptera novaeangliae) mother–calf pairs regard changes calf length an undisturbed breeding/resting ground off Exmouth Gulf, Western Australia. Methods Data were collected from August October 2018 2019 lactating mothers that predominantly the surface with calf. Focal follows (n = 101) conducted using unmanned aerial vehicle obtain detailed video behaviours respirations (23.7 h). Body measurements individual whales calculated still frames. Key results Results ranging ~4–8 m demonstrated respiration rate decreased increased presence activity (P < 0.001). Calf inter-breath intervals became longer duration 0.01). level remained constant, logging for 53% time logging. Maternal low did not differ respect maternal or length. Conclusions highlighted importance grounds preservation, which benefits calves’ rapid growth before polar waters. Implications Findings present largely population serve as baseline understanding impacts anthropogenic disturbance globally.