Behavioural context of call production in humpback whale calves: Identification of potential begging calls in a Mysticete species

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
traveling 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.