Oceans apart: conservation models for two temperate penguin species shaped by the marine environment

Oceanographic productivity patterns in the breeding areas of Magellanic penguins Spheniscus magellanicus in the Atlantic differ from those of Humboldt penguins S. humboldti in the Pacific. We used satellite telemetry to compare foraging trips between 2 Humboldt penguin females with chicks and 44 Magellanic penguin females with eggs or chicks. The Humboldt penguins took trips of short duration and distance, with fewer than 10% of locations > 25 km from the colony. Magellanic penguins traveled longer and more variable distances. Only 24% of locations during chick rearing were within 25 km of the colony; all 8 incubation trips reached distances greater than 100 km. Among Magellanic penguins, foraging trip duration was significantly correlated with distance from the colony during all stages of the breeding season (incubation r(2) = 0.66; early chick r(2) = 0.75; late chick r(2) = 0.91). For each hour of trip duration, penguins ranged nearly 1 km farther from the colony. For the 2 Humboldt females, trip duration was correlated with maximum distance from the colony for one female but not the other, whose trip duration varied little. Trip duration for Magellanic penguins determined by nest checks was correlated with duration determined by satellite telemetry (r(2) = 0.96), making nest checks a potentially inexpensive and minimally disturbing estimator of foraging trip distance and changing food availability. The large difference in foraging distance between the species reflects the distribution of productivity in their foraging areas and shows that protecting the species requires conservation models that are effective on different spatial scales.