ECOLOGÍA TRÓFICA DE ELEFANTES MARINOS DEL SUR (MIROUNGA LEONINA) MACHOS SUB-ADULTOS Y HEMBRAS ADULTAS PREVIO AL PERIODO DE MUDA EN LA ISLA 25 DE MAYO (ISLA REY JORGE) (ISLAS SHETLAND DEL SUR, ANTÁRCTICA)

PEDRAZA AVILA J.J.; CABALLERO GAITAN S.; NEGRETE J. ; DANERI G. A. ; RIET SAPRIZA F.G.

Congreso; XII Congreso de la Sociedad Latinoamericana de Especialistas en Mamíferos Acuáticos; 2018

Studying the foraging strategies of top predators is critical to understand their ecology and predict ecological responses to environmental climate change. Given that Southern elephant seals (SES), Mirounga leonina, are highly sexual dimorphic, we hypothesize that difference in diet requirements between sexes induce the population to a feeding niche partitioning to reduce competition, in particular after the breeding period, when males and females are depleted of their energy reserves due to previous fasting. The main aim was to study the trophic ecology of sub-adult male and adult female SES during the post- breeding period inhabiting 25 de Mayo-Island (King George Island), Antarctic Peninsula. The objectives were to (a) characterize habitat use (niche width) and trophic position by sex; (b) describe the individual variations in resources use and habitat; and (c) determine differences in foraging strategies between sexes. Dermal tissue of free-ranging sub-adult males (n=31) and adult females (n=29) were collected using a remote biopsy seals darts with PAXARMS rifle during the molting period (February-2016) at Maxwell-Bay (Antarctic Specially Protected Area No.132), 25 de Mayo-Island, South Shetland Islands. Carbon and nitrogen stable isotopes values were determined with a Costech elemental analyzer interfaced with a Thermo-Finnigan mass spectrometer. Isotope values represented the food intake of 13-83 days prior to molting. Bayesian analysis and standard ellipses were obtained using SIBER R-package to detect isotopic patterns that may account for habitat use and trophic variability. The ecological niche was defined as trophic (δ 15 N) and spatial (δ 13 C) dimensions, for which we obtained δ 13 C=-23,00±1,09?; δ 15 N=13,52±0,87? of SES sub-adult males and δ 13 C= -22,65±0,80?; δ 15 N=12,51±0,57? of adult females. There was a significant difference between sexes in their trophic dimension (δ 15 N), with sub- adult males occupying a higher trophic position than females. Additionally, sub-adult males used 80% of the isotopic niche used by adult females, while females only used the 39% of the isotopic niche of sub-adult males. Sub-adult males exhibit a wider trophic and spatial niche, suggesting a consumption of a wide range of prey, from a broader spectrum of trophic levels and geographical areas. This study highlight how sub-adult male and adult female SES from 25 de Mayo Island partition the feeding niche through prey allocation tomaximize their energy intake prior to the molting period.