Abstract
The Guiana dolphin (Sotalia guianensis) is a small-bodied dolphin distributed along the Atlantic coast from Honduras to southern Brazil. It preys on fish, squid and shrimps. Several seminal studies have described its diet, yet relationships between the species’ feeding plasticity and climate gradients remain unknown. We compiled a large database of Guiana dolphin stomach remains from southeast coastal Brazil. We described the species’ diet using a number of descriptors, multivariate analysis of variance to test possible differentiation in diet composition, and the Morisita index to estimate the extent of trophic niche overlap between groups. We also analysed feeding plasticity using a regression tree analysis followed by an ordination analysis. We present new records of prey for the species in Brazil. Our results suggest that the Guiana dolphin has opportunistic feeding habits, which may exhibit the species’ feeding plasticity. Such feeding plasticity is associated with the capability to prey throughout a wide array of climate conditions. From a conservation ecology perspective, we conclude that estuaries—even ones that are over-depleted and succumbing to human impacts—are paramount environments for the Guiana dolphin, serving as important sources of prey for the species and other sympatric marine mammals.
Highlights
The Guiana dolphin (Sotalia guianensis, van Benédén, 1864) is a small-bodied Odontocetus within the Delphinidae family popularly known as boto-cinza in Brazil
We showed the resulting classification with a principal component analysis (PCA) on Guiana dolphin individuals according to preference of prey species (De’ath 2002, Borcard et al 2011, De’ath 2014)
Understanding species food habits is a paramount issue in ecology (Miller and Payne 1964, Pianka 1974, Pianka and Jorgensen 2008)
Summary
The Guiana dolphin (Sotalia guianensis, van Benédén, 1864) is a small-bodied Odontocetus within the Delphinidae family popularly known as boto-cinza in Brazil. It is distributed continuously along the Atlantic coast of Central and South America, from Honduras (15°58’N) to Norte Bay (27°35’), Santa Catarina State, Brazil (Da Silva and Best 1996, Simões-Lopes 1988). It inhabits coastal and shallow waters, protected estuaries and bays. The identification of potential prey species consumed by the Guiana dolphin can help to unveil predator-prey relationships, which in turn can enhance our understanding of the ecological role of dolphins in marine ecosystems (Pauly et al 1998), taking into consideration likely intra- and interspecific trophic overlap and population dynamics (including top-down effects)
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