The Chinstrap Penguin (Pygoscelis antarcticus) is a medium-sized species easily recognized by the thin black line of feathers extending from ear to ear, resembling a strap beneath its chin. These penguins are widely distributed across the Antarctic region. They primarily breed on the Antarctic Peninsula and various sub-Antarctic islands, with major colonies found on the South Shetland, South Orkney, and South Sandwich Islands.
The Dominance of Krill
The Chinstrap Penguin’s diet is characterized by an extremely high reliance on a single prey item: Antarctic Krill (Euphausia superba). Krill frequently constitutes the vast majority of the diet, often making up over 90% of the food consumed by weight, especially during the breeding season. In some studies, krill has accounted for more than 99% of analyzed stomach contents. The Chinstrap Penguin is considered a krill specialist, making it highly susceptible to fluctuations in the crustacean’s abundance.
This massive consumption of krill meets the high energy demands of adult penguins and their rapidly growing chicks. Antarctic Krill provides a rich source of fat and protein, essential for fueling rigorous foraging trips and successful chick rearing. The high-fat content ensures parents build up sufficient energy reserves while providing a concentrated meal for their young.
Supplemental Prey and Regional Differences
While krill is the primary food source, the diet is supplemented by other marine organisms, demonstrating opportunistic feeding. Secondary prey items include small fish, such as myctophids (lanternfish) and silverfish, along with small cephalopods like squid. These items are generally minor components, often contributing less than 1% of the total diet by weight in krill-rich areas.
The consumption of these supplemental prey items increases when krill availability is low or when the krill are smaller than usual. This dietary flexibility allows the penguins to target fish more heavily in specific years or regional areas where krill swarms are less dense. This shift helps offset the nutritional deficit when the preferred food source is scarce.
Foraging Tactics
Chinstrap Penguins are pelagic feeders, hunting for prey in the open water column and often traveling significant distances from their colonies. They employ pursuit-diving, using powerful flippers to “fly” underwater and actively chase down krill swarms. These penguins are fast swimmers, capable of reaching speeds up to 18 miles per hour (30 kilometers per hour) in short bursts.
Foraging dives are typically shallow, with about 90% recorded at depths less than 45 meters, and many staying within the top 10 meters of the surface. This shallow pattern targets krill, which often ascend toward the surface at night, a phenomenon known as vertical migration. The average duration of a foraging dive is relatively short, around 72 seconds.
The penguins concentrate their foraging effort during daylight hours and a secondary peak around midnight, coinciding with the movement of their krill prey. Although most dives are shallow, they have been recorded reaching maximum depths up to 70 meters, and occasionally up to 126 meters when targeting deeper-dwelling fish. Varying diving depth allows them to successfully track and exploit krill swarms throughout the day and night.