Data from: High suckling rates and acoustic crypsis of humpback whale neonates maximise potential for mother–calf energy transfer

1. The migration of humpback whales to and from their breeding grounds results in a short, critical time period during which neonatal calves must acquire sufficient energy via suckling from their fasting mothers to survive the long return journey. 2. Understanding neonate suckling behaviour is critical for understanding the energetics and evolution of humpback whale migratory behaviour and for informing conservation efforts, but despite its importance, very little is known about the details, rate and behavioural context of this critical energy transfer. 3. To address this pertinent data gap on calf suckling behaviour, we deployed multi-sensor Dtags on eight humpback whale calves and two mothers allowing us to analyse detailed suckling and acoustic behaviour for a total of 68·8 h. 4. Suckling dives were performed 20·7 ± 7% of the total tagging time with the mothers either resting at the surface or at depth with the calves hanging motionless with roll and pitch angles close to zero. 5. Vocalisations between mother and calf, which included very weak tonal and grunting sounds, were produced more frequently during active dives than suckling dives, suggesting that mechanical stimuli rather than acoustic cues are used to initiate nursing. 6. Use of mechanical cues for initiating suckling and low level vocalisations with an active space of <100 m indicate a strong selection pressure for acoustic crypsis. 7. Such inconspicuous behaviour likely reduces the risk of exposure to eavesdropping predators and male humpback whale escorts that may disrupt the high proportion of time spent nursing and resting, and hence ultimately compromise calf fitness. 8. The small active space of the weak calls between mother and calf is very sensitive to increases in ambient noise from human encroachment thereby increasing the risk of mother–calf separation.1. 座头鲸往返繁殖地的洄游行为，会催生一段短暂且关键的时期：新生幼崽必须通过吮吸空腹母体获取充足能量，方能在漫长的返程旅程中存活。2. 阐明新生幼崽的吮吸行为，对于解析座头鲸洄游行为的能量学机制与演化规律、为物种保护工作提供科学参考均具有关键意义；但尽管该行为至关重要，学界目前对这一关键能量传递过程的细节、速率及行为背景仍知之甚少。3. 为填补幼崽吮吸行为研究中的关键数据空白，我们在8头座头鲸幼崽与2头母体身上部署了多传感器D标签（Dtags），累计获得总计68.8小时的详细吮吸与声学行为分析数据。4. 吮吸潜水行为占总标记时长的20.7±7%：此时母体或在海面休憩，或处于水下深处，幼崽则保持静止悬挂状态，其横滚角与俯仰角均接近0。5. 母子间的发声行为（包含极微弱的单音调声与呼噜声）在活跃下潜时的发生频率高于吮吸潜水时，这表明母子启动哺乳依赖的是机械刺激而非声学线索。6. 启动吮吸依赖机械刺激，且母子间低声发声的有效作用空间不足100米，这表明声学隐蔽（acoustic crypsis）受到了极强的自然选择压力。7. 这种低调的行为或可降低幼崽暴露于窃听型捕食者、以及可能干扰哺乳与休憩时间占比的雄性座头鲸护航个体的风险，最终避免幼崽适合度受损。8. 母子间微弱叫声的极小有效作用空间，对人类活动引发的环境噪声增加极为敏感，进而提升了母子分离的风险。