Dear MARMAM community On behalf of my co-authors I am pleased to share our Behavioural Note titled: Guiana dolphins use mangrove margins as a natural barrier to chase fish prey. Links to access and download the paper:https://onlinelibrary.wiley.com/doi/10.1111/eth.13411 https://doi.org/10.1111/eth.13411 Abstract The behavioral plasticity among and within cetacean species can be driven by their prey sources, local adaptations to environmental features, and/or interactions with human activities. One of the tactics displayed by cetaceans is the barrier feeding, in which individuals or groups herd fish schools against natural and non-natural barriers to restrict movements of their prey. Coastal odontocetes, for example, are known for using shorelines and underwater slopes to trap their prey. Here, we documented two distinct populations of Guiana dolphin using the mangrove margins as a natural barrier to herd and capture fish. The observations took place in the Cananéia estuary, São Paulo State, southeastern Brazil, and in the Paranaguá estuary, Paraná State, southern Brazil. A total of 63 dolphins over eight encounters were observed performing six different events using mangroves as a natural barrier, summing both study areas. These findings not only expand our understanding of the behavior plasticity of the species but also call attention to the importance of the mangrove ecosystem directly to Guiana dolphins and indirectly to the components of their food web. We hope you enjoy the reading. Please feel free to contact me to request a PDF version or for any question or comment regarding our work at: juliapierry@yahoo.com.br Best wishes Julia Cavalli Pierry PhD Student Universidade Federal do Paraná, Brazil.