Prey composition and nutritional strategies in two sympatric pinnipeds

DENUNCIO, PABLO; GANA, JOAQUÍN C.M.; GIARDINO, GISELA V.; RODRÍGUEZ, DIEGO H.; MACHOVSKY-CAPUSKA, GABRIEL E.

JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY

ELSEVIER SCIENCE BV

Año: 2021 vol. 545

0022-0981

Niche segregation has been recognized as a valuable mechanism for sympatric species to reduce interspecificcompetition and facilitate coexistence. The differential use of habitats is one of the behavioural mechanisms thatmay shape coexistence among marine predators. In this study, we provide a dietary and nutritional assessment oftwo pinnipeds, the South American sea lion (SASL) and the South American fur seal (SAFS) and explore theirsympatric coexistence within the Warm Temperate Southwestern Atlantic biogeographic province (WTSAprovince). Pelagic prey species within the WTSA province showed significantly higher proportional compositionof lipids than demersal counterparts, evidencing a nutritional variability in a vertical dimension accessible tomarine predators. By modelling the dietary niches of these pinnipeds through a nutritional lens, we showed highoverlapping prey composition niche breadths suggesting that both species consumed prey with similar nutritionalcomposition; however, distinct realized nutritional niches showed that diets are likely shaped by differencesin foraging behaviours. The SAFS combined pelagic and demersal prey, whereas SASL mostly preyed upondemersal species. This paper provides crucial information on how nutritional variability in the water columnlikely drives the feeding strategies of both pinnipeds in the WTSA province. Given that this variation can influencethe stability of the contrasting population trends shown by these two pinnipeds, nutritional dynamicsmust be taken into consideration when defining conservation strategies.