Elephant seal foraging dives track prey distribution, not temperature: Comment on McIntyre et al. (2011)

McIntyre et al. (2011; Mar Ecol Prog Ser 441:257−272) concluded that climate change-related ocean warming may lead to deeper foraging dives by southern elephant seals as their prey is forced into deeper depths. They further assert that fitness for the seals will be reduced because of greater physiological costs for deep dives and the assumption that deep foraging is less successful. Their conclusions are based on an observed correlation between a temperature index and elephant seal diving depth but do not include any observations of prey. We recently observed pronounced differences in the vertical distribution of pelagic biota—biota that may well include elephant seal prey—across the same frontal zone considered by McIntyre et al. (2011) and believe that their suggested link between temperature and diving depth is actually a link between predators and distinct prey fields—a reflection of adaptive foraging behaviour in a complex and dynamic pelagic system. As such, the analysis of McIntyre et al. (2011) is uninformative about likely impacts of ocean warming.