Environmental factors related to group size and habitat use of Guiana dolphins from São Marcos Bay, Amazon coast
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Environmental changes can affect the social structure and disrupt habitat use of marine mammal species. An impact on the social dynamics of dolphins, including group size structure, may attenuate the feeding success and increasing predation risk, especially considering species exhibiting small home ranges, which impose particular habitat dependency and high vulnerability to environmental changes. In this regard, the Guiana dolphin (Sotalia guianensis, Van Benéden, 1864) is a particularly endangered species due to its coastal distribution and considerable small home range. The aim of this study was first to conduct a spatial assessment of the dolphin groups sighted in the São Marcos Bay (SMB; Northeastern Brazil), one of the most important port areas in Brazil. The results show an overlap between the distribution of the dolphin groups and the port activities area, which includes the loading zone at the main port area and the navigation channel used by large cargo ships and other vessels. Also, a GLM regression was conducted to identify the best combination of selected variables that best predict the group size of the dolphins. The predictor variables included: salinity, sea surface temperature, depth, water transparency, distance from the main port area, and the feeding activity of the groups sighted. The results indicated that larger dolphin groups were found in areas closer to the main port area and were associated with foraging activities. Therefore, the results suggest that this dolphin population might be exposed to threats linked to the port activities, which may include noise pollution, vessel collision, and chemical pollution.
KeywordsAmazon coast Brazil Environmental change Group size Guiana dolphin Sotalia guianensis
We would like to thank our boat captain Cabelo for his enthusiasm and professionalism during the research survey.
This study was funded by the Deutscher Akademischer Austauschdienst (DAAD) via the project COMPLEX (Grant Nr. 57384894/08).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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