Foraging zones of royal penguins during the breeding season, and their association with oceanographic features

Satellite transmitters were deployed on breeding royal penguins at Macquarie Island during 4 stages (first male foraging trip during incubation, n = 2; first female foraging trip during incubation, n = 3; guard, n = 4; and early creche, n = 1) of the 1994/5 and 1995/6 breeding seasons. From these data, foraging zones, oceanographic features of the zones, and travelling behaviours were determined. Foraging trip length, area of foraging zone, and distance travelled were strongly correlated, and were greatest during incubation. The estimated rate of travel (mean velocity) was constant across individuals and stages in the breeding season. No diurnal patterns in rates of travel were detected, nor any patterns on different days of a foraging trip. A meander coefficient (the degree of linear travel, to give an indication of foraging activity) was constant between stages in the breeding season, and day of the foraging trip, but was greater from 07:00 to 18:00 h, suggesting increased foraging activity. Foraging during all stages of the breeding season was offshore, in deep water (greater than 2000 m) and in the polar frontal zone. During the incubation stage the foraging zones were circular, with a low Foraging Zone Coefficient (FZC: maximum distance from the colony divided by area of the foraging zone), but more direct with a higher FZC after chicks hatched. These different patterns are thought to be associated with prey resources in the region. It is concluded that the foraging behaviour of royal penguins is closely Linked to the polar frontal zone, their prey, and the constraints of the breeding season.