To flee or not to flee: anti-predator response of humpback whales on their breeding ground

Anti-predator behaviors are usually well conserved within species, although they may vary across individuals depending on several factors such as socio-ecological contexts. Using humpback whales ( Megaptera novaeangliae ), we investigated whether the flight anti-predator strategy observed in high-latitude feeding grounds is conserved in low-latitude breeding areas. Playbacks of predatory killer whale (KW) sounds were conducted in mother-calf pairs, some accompanied by a male escort. We quantified whales' behavioral responses using multi-sensor tags and visual observations. We revealed clear directional movements of whales away from the sound source, with a significant increase in speeds and a switch to near-surface movement patterns in response to KW playbacks ( n = 5). Male escorts switched to synchronous surfacing with mothers. In contrast, no or slight responses were observed in response to control playbacks ( n = 4). Our results indicate a cohesive flight anti-predator strategy, conserved on feeding and breeding grounds but complemented by context-dependent social components.