Population variance in prey, diets and their macronutrient composition in an endangered marine predator, the Franciscana dolphin

• Published in: Journal of sea research Vol. 129; pp. 70 - 79
• Main Authors: Denuncio, Pablo, Paso Viola, Maria N., Machovsky-Capuska, Gabriel E., Raubenheimer, David, Blasina, Gabriela, Machado, Rodrigo, Polizzi, Paula, Gerpe, Marcela, Cappozzo, Humberto L., Rodriguez, Diego H.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01.11.2017; Elsevier BV
• Subjects: Aquatic mammals; Brackishwater environment; Cetacea; Cetaceans; Composition; Diet; Dolphins; Dolphins & porpoises; Ecological monitoring; Endangered & extinct species; Energy; Energy management; Environmental impact; Environmental management; Estuaries; Estuarine environments; Information management; Lipids; Macronutrient composition; Marine conservation; Marine mammals; Niches; Nutritional geometry; Pontoporia blainvillei; Population genetics; Populations; Predators; Prey; Proteins; Rare species; Ratios; Seasonal variations; Studies; Subpopulations; Threatened species; Wildlife conservation; Diet; Nutritional geometry; Pontoporia blainvillei; Macronutrient composition; Cetaceans
• ISSN: 1385-1101; 1873-1414
• DOI: 10.1016/j.seares.2017.05.008

Disentangling the intricacies governing dietary breadth in wild predators is important for understanding their role in structuring ecological communities and provides critical information for the management and conservation of ecologically threatened species. Here we combined dietary analysis, nutritional composition analysis of prey, literature data and nutritional geometry (right-angled mixture triangle models -RMT-) to examine the diet of the most threatened small cetacean in the western South Atlantic Ocean, the Franciscana dolphin (Pontoporia blainvillei). We applied a recently developed extension of niche theory based on the RMT to help understand the dietary strategies of this species. Our results showed that across their range the Franciscanas consumed prey with variable protein-to-lipid energy ratios (LMM, p<0.001). In an intensive study of one area, FMA IV, we found that dolphins sub-populations, which recent genetic evidence suggest should be differentiated into three management units, have diets with different protein energy and water mass compositions, but similar protein-to-lipid energy ratios. Furthermore, dolphins from the three areas mixed different combinations of prey in their diets to achieve the observed macronutrient ratios. These results suggest that the different habitats that each sub-population occupies (estuarine, north marine area and south marine) might be associated with different prey composition niches, but similar realized nutritional niches. Future priorities are to better comprehend possible geographical and long-term seasonal effects on prey consumption and dietary breadth of the different Franciscana populations to identify potential impacts (environmental and human-related), enhance the current management strategies to protect this endangered marine predator. •Prey consumed by Franciscanas differs in their protein-to-lipid energy ratios.•We estimated minimal prey composition and realized nutritional niches as a vital tool to enhance conservation strategies.•Franciscana sub-populations in FMA IV forage in different habitats and occupy different prey composition niches.