Determining the spatial distribution of an Antarctic top predator using passive acoustics.

Abstract

The leopard seal (Hydrurga leptonyx) is one of four species of ice seals in Antarctica with each species occupying a distinct position in the Antarctic sea‐ice ecosystem. Ice seals offer a potential source of information about ecosystem interactions and environmental variability integrated over a variety of spatial and temporal scales. During the austral spring and summer, leopard seals move within the pack ice to breed. Acoustic surveying is necessary to assess their distributions as male leopard seals vocalize underwater as part of their breeding display. During the 1999/2000 austral summer, the relative abundance of adult male leopard seals was determined using underwater passive acoustic point‐transect surveys. The abundance data were combined with environmental data in a geographical information system, and a model was developed to determine what factors of the environment are correlated with their abundance and distribution. The model with the best predictive power showed a trend of increased abundance toward the pack ice edge. These regions are associated with areas of increased foraging potential suggesting that the distribution of leopard seals off Eastern Antarctica is influenced, in part, by increased availability of prey.