Social Interactions Between Tucuxis and Bottlenose Dolphins in Gandoca-Manzanillo, Costa Rica

Studies measuring the extent of interspecific interactions between dolphin species are rare. We observed free-ranging tucuxis (Sotalia fluviatilis) and bottlenose dolphins (Tursiops truncatus) to document the frequency of occurrence of interspecific interactions relative to group size and behavioral state. We conducted opportunistic surveys in Gandoca- Manzanillo (9º36’N, 82º35’W), Costa Rica. Of the 71 groups analyzed, 46.5% were comprised only of tucuxis, 21.1% of bottlenose dolphins, and 32.4% of the two species. Social behavior was more frequent in mixed-species groups and in groups larger than four dolphins; foraging was more frequent in single-species groups and in groups smaller than five dolphins. Photographic documentation and sightings of putative hybrids suggest the occurrence of hybridization between both dolphin species. Results indicate that tucuxis and bottlenose dolphins interacted frequently and that these interactions were predominantly social in nature. Future studies will discern whether these interactions result in the development of hybrids

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