Behavioral Repertoire of Lahille’s Bottlenose Dolphins During the “cooperative Fishing” With Artisanal Fishers

Abstract

Many human cultures have been established by positive interactions with wildlife over the last centuries. Lahille’s bottlenose dolphins (Tursiops gephyreus), for example, have historically developed tactics for coastal and estuarine foraging, which sustains a fishing art known as “cooperative fishing” by traditional fishers in estuaries of southern Brazil. Using Unmanned Aerial Vehicles footage, in this study, we explored the behavior of the Lahille’s bottlenose dolphins in the Tramandaí Inlet. We focused on how their behavior repertoire was related with the frequency of net casting by fishers. Close to eight hours of aerial footage recorded from June 2017 to May 2018 were analyzed. Our observations comprise mainly dolphins foraging in the estuary inlet when fishers were present along the shoreline. Dolphins performed at least 25 clearly distinct behaviors and three types of movement patterns. A Generalized Additive Model supported that the fishers interpret a subset of this repertoire (64%) as cues for throwing their cast nets. The behavioral overview of the Lahille’s bottlenose dolphins presented here demonstrates not only a diverse repertoire for this population, but also its clear influence on fishers’ activities. It is clear that ethological, scientific and traditional perspectives should be integrated to better understand the ecological significance of this cooperative fishing, for both dolphin populations and fishers that depend on them.