Abstract
Baleen whale calves vocalize, but the behavioural context and role of their social calls in mother-calf interactions are yet to be documented further. We investigated the context of call production in humpback whale (Megaptera novaeangliae) calves using camera-equipped animal-borne multi-sensor tags. Behavioural states, including suckling sessions, were identified using accelerometer, depth and video data. Call types were categorized through clustering techniques. We found that call types and rates predict the occurrence of a given state. Milling, resting and travelling were associated with a median call rate of 0 calls min(-1), while surface play, tagging responses and suckling were associated with higher call rates, averaging up to a median of 0.5 calls min(-1) for suckling. Suckling sessions were mainly associated with two sets of low-frequency calls corresponding to previously described burping, barking and snorting sounds. Surface play sessions featured mid-frequency calls with whoop-like sounds and other call types. These results address the significance of vocal signalling in mother-calf communication and the calf's development, including the first identification of potential begging calls. Overall, this study offers new insights into baleen whale behaviour, underscores the importance of social calls in mother-calf interactions and enhances our understanding of communication systems in aquatic mammalian mother-young pairs.