Dietary analysis of Weddell seals (Leptonychotes weddellii) as concluded from scat collection in McMurdo Sound, Antarctica
Degree GrantorUniversity of Canterbury
Degree LevelPostgraduate Certificate
Degree NamePostgraduate Certificate in Antarctic Studies
Weddell seals (Leptonychotes weddellii) in McMurdo Sound have a long history of dietary analyses, with understanding their feeding ecology essential to determining ecological role, trophic links, and prey consumption in the Ross Sea. Twenty-one faecal samples collected in summer 2009 revealed a diet primarily dominated by fish – the tentatively identified nototheniid Pleuragramma antarcticum in particular – with over 83% of samples exhibiting some evidence of piscines. Despite this, often a large percentage of samples will not contain identifiable otoliths, and as such no direct confirmation for the believed major prey item Antarctic toothfish (Dissostichus mawsoni) consumption was exhibited, especially with the tendency for Weddell seals to avoid eating the head, skin, and vertebral column. The excessive presence of plankton (in 100% of samples) has led to supporting the proposal of secondary ingestion, and similar theories have been applied to the occurrence of rocks and stones (in over 16% of samples). With all this uncertainty, the future of dietary analysis in Weddell seals is moving away from taxonomic identification of faecal hard parts, and more towards molecular methods such as DNA and stable isotope analysis, as combined methods tend to have a greater success rate than singular identification techniques.