Dear colleagues, We are pleased to share our recent paper in PNAS on the benefits of juvenile social play in male bottlenose dolphins: Holmes KG, Krützen M, Ridley AR, Allen SJ, Connor RC, Gerber L, Flaherty Stamm C, King SL. Juvenile social play predicts adult reproductive success in male bottlenose dolphins. Proceedings of the National Academy of Sciences. 2024 Jun 18;121(25):e2305948121. Abstract: For over a century, the evolution of animal play has sparked scientific curiosity. The prevalence of social play in juvenile mammals suggests that play is a beneficial behavior, potentially contributing to individual fitness. Yet evidence from wild animals supporting the long-hypothesized link between juvenile social play, adult behavior, and fitness remains limited. In Western Australia, adult male bottlenose dolphins (Tursiops aduncus) form multilevel alliances that are crucial for their reproductive success. A key adult mating behavior involves allied males using joint action to herd individual females. Juveniles of both sexes invest significant time in play that resembles adult herding— taking turns in mature male (actor) and female (receiver) roles. Using a 32-y dataset of individual-level association patterns, paternity success, and behavioral observations, we show that juvenile males with stronger social bonds are significantly more likely to engage in joint action when play-herding in actor roles. Juvenile males also monopolized the actor role and produced an adult male herding vocalization (“pops”) when playing with females. Notably, males who spent more time playing in the actor role as juveniles achieved more paternities as adults. These findings not only reveal that play behavior provides male dolphins with mating skill practice years before they sexually mature but also demonstrate in a wild animal population that juvenile social play predicts adult reproductive success. The paper can be accessed here: https://www.pnas.org/doi/full/10.1073/pnas.2305948121 or you can DM me for a copy. All the best on behalf of all coauthors, Katy --