Hi all, My coauthors and I are excited to share our recent open access paper describing movement and acoustic behavior in humpback whale yearlings: Zeh, J.M., Lammers, M.O., Pack, A.A. Parks, S.E*.* Movement and sound production in yearling humpback whales: age-class comparisons. *Behav Ecol Sociobiol* 79, 36 (2025). https://doi.org/10.1007/s00265-025-03575-7 Abstract: The juvenile period is an important stage of growth and development across animals, often consisting of graded stages of physical and social development. For cetaceans, locomotor and social development are key to survival after weaning; individuals require dive capabilities for successful foraging and navigating their aquatic habitat as well as robust acoustic signaling abilities to mediate complex social interactions. Although adult diving and sound production behavior have been studied, little is known about the development of these abilities of juvenile baleen whales. To address this gap in our understanding of baleen whale ontogeny, we used suction cup sound and movement recording tags deployed on 11 humpback whales (3 calves, 5 yearlings, and 3 adults) on their breeding ground in Hawai’i. We recorded deeper and longer dives and shorter intervals at the surface for yearlings compared to calves, suggesting increased aerobic capacity for diving in yearlings. A contact call commonly produced by adults was recorded on yearling tags but not detected from any of the tagged calves, reflecting development in social signaling with age. These data provide an important preliminary understanding of development and differences across age classes. Based on the tag data, yearlings appear to occupy an intermediate state of development, approaching the dive and sound production abilities of adults, and showing evidence of physiological maturation during the first year of life. Best, Julia Zeh, PhD *Passive Acoustics Branch* Northeast Fisheries Science Center NOAA Fisheries | U.S. Department of Commerce