Guarding against oversimplifying the fundamental drivers of southern elephant seal population dynamics

Recently, Vergani et al. (2008) examined the climatic drivers of population dynamics (weaning mass) and foraging performance (diet variation) from southern elephant seals, Mirounga leonina, in the Atlantic sector of the Southern Ocean. The principal conclusion was that elephant seal weaning masses were greater in La Ninã years, when higher ocean temperatures persisted in areas where most seals from the study population at King George Island forage. The authors infer that these conditions lead to improved prey quality and quantity; however, many of the questions and hypotheses they posed have already been addressed elsewhere in the Southern Ocean. We argue that substantial speculation and uncertainty could have been avoided by the authors had they consulted and examined this considerable available literature that confirms (and in some cases, fails to support) many of their conclusions. Such a spatially limited focus in biogeography increases the risk of making important errors of interpretation.