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

• Published in: Functional Ecology
• Main Authors: Videsen, Simone K. A., Bejder, Lars, Johnson, Mark, Madsen, Peter T.
• Other Authors: European Commission, University of St Andrews. School of Biology, University of St Andrews. Marine Alliance for Science & Technology Scotland, University of St Andrews. Sea Mammal Research Unit, University of St Andrews. Sound Tags Group, University of St Andrews. Bioacoustics group, University of St Andrews. Scottish Oceans Institute
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2018
• Subjects: Bio-energetics; Humpback whale; Migration; Neonate; Nursing; Suckling; QH301 Biology; DAS; QH301; Murdoch; Humpback Whale
• Online Access: http://hdl.handle.net/10023/13227; https://doi.org/10.1111/1365-2435.12871; http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.12871/full#footer-support-info

This work was funded by a Sir Walter Murdoch Honorary Professorship along with Carlsberg and FNU funding to P.T.M. L.B. was funded by Murdoch University, and M.J. was funded by the Marine Alliance for Science and Technology, Scotland, and by a Marie Curie Career Integration Grant. Data for this paper are deposited in the Dryad Digital Repository https://doi.org/10.5061/dryad.m8j17 (Videsen et al. 2017). 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 ...