The Yellow-Eyed Penguin (Megadyptes antipodes), known in Māori as the Hoiho, is a unique and endangered species found only in New Zealand. As one of the world’s rarest penguins, its survival is closely tied to the health of the surrounding marine environment. Understanding its specialized diet is fundamental to conservation efforts aimed at protecting this vulnerable population.
Primary Prey Species
The Yellow-Eyed Penguin’s diet is primarily composed of small to medium-sized fish and cephalopods; fish make up approximately 90% of the total food intake by weight. Their hunting strategy is distinct because they are predominantly benthic foragers, meaning they catch prey at or near the seafloor. This reliance on the sea bottom dictates the types of species they consume.
Key fish species include Opalfish (Hemerocoetes monopterygius), Silversides (Argentina elongata), and Sprat (Sprattus antipodum). Historically, Red Cod (Pseudophycis bachus) was a significant component, but recent studies show a shift toward Blue Cod (Parapercis colias). Cephalopods, most notably the Arrow Squid (Nototodarus sloanii), are the second major prey group, making up the remaining 10% of the diet.
Most prey items consumed are less than 200 millimeters in length. The shift from Red Cod to Blue Cod is a concern because Blue Cod are often consumed at a larger size, which can negatively affect chick survival. This dependence on specific demersal (bottom-dwelling) species also makes the penguins’ food source vulnerable to changes in the benthic ecosystem.
Foraging Distance and Diving Depth
The Yellow-Eyed Penguin’s foraging behavior involves consistent dives to the seafloor to secure benthic prey. When breeding, penguins concentrate hunting efforts within a 10 to 40 kilometer radius of their colony. They may travel up to 25 kilometers offshore on a standard day trip to find food for their offspring.
Non-breeding adults or those that failed to raise chicks have a much greater range, sometimes traveling 60 kilometers or more from the coast. The average dive depth is around 61 meters, often displaying a characteristic U-shape indicating time spent foraging on the bottom. While typical dives are in the 30- to 60-meter range, these penguins can reach maximum depths of 150 to 160 meters, and in some areas, up to 240 meters.
The duration of these deep foraging excursions is relatively short, with a mean dive time of about two minutes. The maximum recorded dive duration is approximately 3.9 minutes. Up to 90% of all dives performed are benthic dives, confirming their unique strategy compared to other penguin species that hunt in the open water column.
Seasonal and Chick Feeding Changes
The Yellow-Eyed Penguin’s diet and foraging effort change significantly across the year, especially between non-breeding and breeding seasons. During the breeding season, parents must meet the high caloric and protein demands of their growing young. This requirement restricts their time at sea and their overall foraging range, necessitating a return to the nest at least once daily to feed their chicks.
After the chicks hatch, one parent guards the nest while the other forages, a pattern that continues for the first six weeks. Once the chicks are older, both parents forage simultaneously to supply the necessary food. This food is delivered as a regurgitated mixture of partially digested fish and squid, and the size and type of prey brought back is important for the health of the young.
Larger prey, such as adult Blue Cod, can be challenging or impossible for chicks to ingest, even if suitable for the adult. Dependence on these larger species can lead to chick starvation and lower reproductive success in poor food years. Non-breeding penguins, free from the daily commitment of feeding young, travel longer distances and for more extended periods, showing greater flexibility in their foraging patterns.