Abstract
Understanding how animal behavior varies across lifespan is important to understanding their ecology, evolution, and conservation, especially for long-lived species. Using over a decade worth of whale watch data, I investigated how age, sex, female reproductive class, and temporal variation structure surface feeding and aerial behaviors in humpback whales (Megaptera novaeangliae) in the southwestern Gulf of Maine feeding ground. Additionally, I analyzed the timing of apparent separation of mother-calf pairs to better understand maternal care and calf development. I used mixed models to evaluate variation in four surface feeding behaviors (bubble net feeding, bubble cloud feeding, kick feeding, and lunge feeding). I tested for agebased shifts in feeding strategy, sex-specific differences, and patterns associated with female reproductive stage. Variation in feeding behavior was strongly associated with age, with lunge feeding most common in early age classes and more complex bubble and kick feeding prevalent in older age classes. Sex and female reproductive classes had minimal associations with feeding variation. I also examined high-energy aerial behaviors (breaches, head breaches, tail breaches, lobtails, and flipper slapping). These aerial behaviors showed variation across age classes and reproductive classes, with flipper slapping showing high probabilities in calves and NPNL females, while breaching was elevated in lactating females. To assess seasonal dynamics, I used generalized additive mixed models to evaluate day-of-year trends in both surface feeding and aerial behaviors for calves, juveniles, and adults. Aerial behaviors became increasingly linear with age, while feeding became nonlinear with age with majority of feeding behaviors peaking in the fall and spring. While demographic trends were evident, random effects in the statistical models revealed substantial individual-level variation. Finally, I analyzed mother-calf pairings and documented 25 apparent calf separations from their mothers, representing the most extensive compilation of documented humpback whale mother-calf separation intervals on a feeding ground in the published literature. These findings demonstrate that humpback whale behavior on feeding grounds is not homogeneous across individuals, and is structured by age, female reproductive class, and temporal context. This research advances our understanding of behavioral ontogeny in humpback whales by showing that feeding and aerial behaviors vary systematically across age, sex, and reproductive class, highlighting feeding grounds as key sites of behavioral differentiation.