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

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.

JOURNAL OF SEA RESEARCH

ELSEVIER SCIENCE BV

Año: 2017

1385-1101

Disentangling the intricacies governing dietary breadth in wild predators is important for understanding theirrole in structuring ecological communities and provides critical information for the management and conservationof ecologically threatened species. Here we combined dietary analysis, nutritional composition analysisof prey, literature data and nutritional geometry (right-angled mixture triangle models -RMT-) to examinethe 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 helpunderstand the dietary strategies of this species. Our results showed that across their range the Franciscanasconsumed 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 differentiatedinto three management units, have diets with different protein energy and water mass compositions, but similarprotein-to-lipid energy ratios. Furthermore, dolphins from the three areas mixed different combinations of preyin their diets to achieve the observed macronutrient ratios. These results suggest that the different habitats thateach sub-population occupies (estuarine, north marine area and south marine) might be associated with differentprey composition niches, but similar realized nutritional niches. Future priorities are to better comprehendpossible geographical and long-term seasonal effects on prey consumption and dietary breadth of the differentFranciscana populations to identify potential impacts (environmental and human-related), enhance the currentmanagement strategies to protect this endangered marine predator.