Colony-specific foraging areas of lactating New Zealand fur seals

Abstract

During 2005 and 2006, 21 lactating New Zealand fur seals Arctocephalus forsteri were tracked from 4 breeding colonies in southern Australia. The distance between colonies ranged between 46 and 207 km. In total, 101 foraging trips were recorded (2 to 19 trips ind.–1). Seals initiated foraging trips on a colony-specific bearing (Cape Gantheaume 141 ± 34°, Cape du Couedic 188 ± 12°, North Neptune Island 204 ± 12° and Liguanea Island 235 ± 19°). During autumn, seals from Cape du Couedic, North Neptune Island and Liguanea Island predominantly targeted distant oceanic waters associated with the subtropical front (STF), while seals from Cape Gantheaume targeted shelf waters associated with a seasonal coastal upwelling, the Bonney upwelling. The distance of each colony from the STF (based on the preferred colony bearing) or the Bonney upwelling in the case of Cape Gantheaume was correlated with the maximum straight-line distances travelled (Cape Gantheaume 119 ± 57 km, Cape du Couedic 433 ± 99 km, North Neptune Island 564 ± 97 km and Liguanea Island 792 ± 82 km). The organisation of colony-specific foraging grounds appears to be influenced by the proximity of colonies to predictable local upwelling features, as well as distant oceanic frontal zones. Knowledge of whether New Zealand fur seals utilise colony-specific foraging grounds may be important in predicting and identifying critical habitats and understanding whether management requirements are likely to vary between different colonies.