The cephalopod prey of the Weddell seal, Leptonychotes weddellii, a biological sampler of the Antarctic marine ecosystem

International audienceWeddell seals, Leptonychotes weddellii, areimportant apex predators in the food web of the Antarcticmarine ecosystem. However, detailed information on theirtrophic relationships with cephalopods is scarce. Moreover,cephalopods play a key role in the marine environment, butknowledge of their feeding habits is limited by lack of data.Here, we have combined the use of this seal as a biologicalsampler together with measurements of the stable isotopicsignature of the beaks of their cephalopod prey. Thus, theaims of the present study were: (1) to examine in detail thecephalopod portion of the diet of Weddell seals by meansof scat analysis and (2) to assess the habitat use and trophiclevel of the different cephalopod prey taxa identified. FromJanuary to February 2009, a total of 48 faecal droppingswere collected at Hope Bay, Antarctic Peninsula. Cephalopodswere mainly represented by beaks (n = 83) whichwere identified to the lowest possible taxonomic level.Furthermore, subsamples of beaks were separated for furtherisotopic analysis. Relative abundance of stable isotopesof carbon (d13C) and nitrogen (d15N) was determined by continuous-flow isotope-ratio mass spectrometry.Cephalopods were represented uniquely by octopods of thesubfamily Eledoninae. Pareledone turqueti was the dominantprey species followed by the papillated Pareledonespecies group and Adelieledone polymorpha. We concludethat Weddell seals preyed primarily on benthic preyresources. Furthermore, the relatively similar d13C andd15N values in beaks of the three octopod prey taxa suggestthat these share the same type of habitat and occupy similartrophic level positions