Dear colleagues, My co-authors and I are pleased to share our new publication in *Marine Ecology Progress Series* entitled: Energetic scaling of propulsive costs across body sizes in humpback whales
I am happy to share a copy of the publication with anyone interested! You can reach me at the following email address: [email protected] Abstract: Movement is energetically expensive, and locomotor efficiency depends on body size and morphology. Humpback whales Megaptera novaeangliae exhibit a remarkable ontogenetic size range and experience periods of intense fasting coinciding with energetically demanding migration, lactation, and growth. To quantify how propulsive costs scale with body size, we combined accelerometry data and aerial photogrammetry collected from 62 humpback whales ranging from calves to adults (4.4–14.1 m) on their Hawaiian breeding ground. Using a hydrodynamic model incorporating swimming kinematics and morphology, we found that mass-specific propulsive costs declined with increasing body length, representing a 62 % reduction between a 4 m calf and a 14 m adult. Elevated activity levels and higher mass-specific propulsive costs in calves energetically burden lactating females, whose energy reserves must support both calf activity and rapid somatic growth. These energetic demands are buffered by the female’s own reduced activity and mass-specific propulsive costs. We estimate that propulsion accounts for approximately 21% of a lactating female’s daily energetic expenditure while on the breeding grounds. Our approach highlights the disproportionately higher cost of displacement in smaller individuals, ranging from approximately 4 kJ/m in calves to 25 kJ/m in adults, providing a scalable framework to quantify the energetic consequences of disturbance. These findings underscore the importance of large body size in baleen whales, refine understanding of how activity costs scale across body size in humpback whales on their breeding grounds, and provide an energetic baseline to predict consequences of environmental and anthropogenic disturbance. Best, Cameron
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