Collaborative Research: Hunting Behavior and Energetics of Free Ranging Weddell Seals

University Of California-Santa Cruz, Santa Cruz CA

Investigators

Abstract

The focus of this collaborative research project is on the behavioral and energetic adaptations enable Weddell seals to forage in the cold, dark, Antarctic fast-ice environment. To answer this question, hypotheses related to general foraging strategy, foraging location, searching mode, prey detection, locomotor performance, the cost of diving and foraging efficiency of free-ranging Weddell seals (Leptonychotes weddellii) will be tested. In addition, locomotor performance and behavior during diving to estimate the costs associated with hunting and the benefits gained from hunting (type and frequency of prey captures) will be examined. This study will provide unique insight into marine mammal foraging tactics and will contribute to fields of physiology (diving and energetics) and ecology (foraging theory and behavioral ecology). The proposed study builds on research on Weddell seals in McMurdo Sound using an animal-borne video system/data logger to record the behavior, physiology and locomotor performance of marine mammals at depth. This provided first observations of Weddell seal hunting strategies, predator-prey interactions and corresponding estimates of diving metabolism. The isolated-ice-hole protocol used in the study allows seals to choose the depth and duration of a dive, but they must return to a single place to breathe, which limits their range of movement. In addition, they are unable to haul out of the water or interact with other seals and may be exposed to lower prey densities than when foraging naturally. The new focus is the behavior and energetics of completely free-ranging seals, for which all significant constraints have been removed. Although the current study has demonstrated important new principles in Weddell seal foraging and has increased understanding of diving behavior and swimming performance, it is now essential to determine whether those principles apply to unconstrained animals. The study will continue to employ a multidisciplinary team of scientists with highly skilled technical support. The results will advance the understanding of the foraging ecology of Weddell seals and create a basis for similar research on other species of marine mammals that are more difficult to study in the open ocean. Finally, by extending the study from an isolated ice hole to completely free-ranging conditions, this research will provide new insight into the role of Weddell seals as apex predators in the Antarctic marine ecosystem.