EXPLOITATION OF PELAGIC RESOURCES BY A NONFLYING SEABIRD - SATELLITE TRACKING OF THE KING PENGUIN THROUGHOUT THE BREEDING CYCLE

We investigated foraging ranges and strategies of king penguins at the Crozet Islands (Southern Ocean) for 19 mo using satellite tracking for the first time in this species. Eighteen penguins were fitted with transmitters to determine foraging behaviour throughout the breeding cycle in relation to oceanographic data. The mean foraging range was 471 +/- 299 km (range 144 to 1489). The total length of trips was 1239 +/- 671 km (range 397 to 3893), i.e. 64 +/- 31 km daily. So, the range of the king penguin is much greater than previously supposed. Two types of track were distinguished, each associated with a different foraging strategy: long and direct trips to predictable marine resources (towards the Polar Front), and, around the time of hatching, shorter circular trips, during which the birds probably fed on less-predictable resources. During winter, trips appeared erratic and were at their longest (at least 3893 km and foraging range > 1488.7 km). There was a change in the length and direction of tracks according to the breeding phase of the king penguin and probably also according to the position of the Polar Front which moves northwards during austral winter and autumn. All the locations of king penguins were restricted to the zone of modified Antarctic waters around the Crozet Islands, where myctophids, the major prey of king penguins, are available between 200 m deep and the surface (5-degrees-C isotherm). Near the Antarctic circumpolar current where cold water masses flow, we found fewer king penguin locations than near the Polar Front where the 5-degrees-C isotherm reaches the surface. We suggest that the foraging ecology of the king penguin is closely related to oceanographic features and the biology of its main prey.