Félix, F. (2025). Fusion of communities, the response of estuarine bottlenose dolphins to population decline in the gulf of Guayaquil, Ecuador. Animal Behavior and Cognition, 12(4), 521-547.  https://doi.org/10.26451/abc.12.04.04.2025

Changes in the social structure of two neighboring communities of estuarine bottlenose dolphins in Ecuador were assessed over 14 years (2011–2024). During this period, 632 surveys were conducted, covering a cumulative distance of 23,171 km. A total of 133 distinct individuals, representing all age and sex classes, were recorded. The annual abundance of dolphins decreased from 50 in 2014 to 24 in 2024, coinciding with a decline in the proportion of non-resident individuals, from 35% to 0%. Changes in the social structure were analyzed across three periods: 2011–2015, 2016–2019, and 2020–2024. Pairwise cluster analyses revealed two distinct communities (El Morro and Posorja) in the first two periods, which merged into a single community in the third period. Significant social changes were observed during this process as the two communities adapted by sharing spaces and resources, altering spatiotemporal patterns, and increasing their time together to benefit from the fusion. Female mixed groups increased from 0% to 77.8%, the inter-community association rate rose from 0.04 to 0.74, and the average group size grew from 8.07 to 11.48 dolphins/group. Reproductive parameters, including calf survival rates and the fertility of Posorja females, improved following the fusion. These findings reveal a high degree of social flexibility within this population, suggesting that even though inshore bottlenose dolphins typically form discrete social units, these structures can adapt and reorganize under certain demographic or social pressures. Given the historical and emerging threats to this population, understanding the drivers of these social dynamics is critical for the long-term conservation of this endangered population.

Tursiops truncatus, Social behavior, Reproductive parameters, Conservation, Ecuador