Dear all, My co-authors and I are pleased to announce and share our recent paper titled *Common dolphin (Delphinus delphis) fission–fusion dynamics in the south coast of Portugal * * Castro, J., Faustino, C., Cid, A., Quirin, A., Matos, F.L., Rosa, R., Pearson, C.H. Common dolphin (Delphinus delphis) fission–fusion dynamics in the south coast of Portugal. Behav Ecol Sociobiol 76, 128 (2022). https://doi.org/10.1007/s00265-022-03235-0 <https://doi.org/10.1007/s00265-022-03235-0>* Abstract: Animals with fission–fusion dynamics live in fluid societies with varying party sizes. The joining (fusion) and separation (fission) of these parties is considered a response to costs and benefits associated with grouping. This study investigates which factors influence grouping and fission–fusion dynamics in common dolphins (Delphinus delphis) in Portugal. Between June and October of 2016 and 2017, 94 boat-based group focal follows were conducted, resulting in 2410, 2-min behavioral samples. Using generalized linear models, we examined how mother-calf pair presence, behavioral state, and temporal variability influence party size. We used generalized estimating equations to model behavior and fission–fusion dynamics, testing the responses to mother-calf presence and time. Parties were smaller when mother-calf pairs were absent or when animals were resting. Socializing parties without mother-calf pairs were more likely to be observed than traveling parties with mother-calf pairs. Compared to traveling, foraging was less likely in September and October than in June, and resting was more likely in September. Compared to stable state, parties without mother-calf pairs were more likely to fission than parties with mother-calf pairs and fusion events became less likely by advancing hour. We revealed that common dolphins in Southern Portugal exhibit a high degree of fission–fusion dynamics that are predominantly influenced by mother-calf presence, confirming the importance of this region as a nursery ground. By assessing fine-scale social dynamics in common dolphins, this study advances understanding of the evolutionary drivers shaping grouping patterns in wild cetaceans while also providing an important comparative counterpoint to terrestrial fission–fusion dynamic. The full paper is available here: <https://www.mdpi.com/2072-4292/13/1/156/htm>https://rdcu.be/cUtQ5 Please contact jmadeiracastro@gmail.com if you would like a copy of the manuscript or if you have any questions. Best regards Joana Castro