70% of Emperor Penguin Chicks Disappear from Antarctica's Largest Breeding Site [Reading Science]

Sharp Decline in Penguin Population on Coulman Island, Ross Sea
Polar Research Institute: "Iceberg Blocked Access to Food"

The number of emperor penguin chicks on Coulman Island in the Ross Sea, one of the largest emperor penguin breeding grounds in Antarctica, has plummeted by about 70% in just one year. The primary cause has been identified as a massive iceberg blocking access to the breeding grounds, which cut off the penguins' food supply.

The Korea Polar Research Institute announced that the number of emperor penguin chicks observed on Coulman Island in the Ross Sea dropped sharply from about 21,000 last year to around 6,700 this year. Since similar phenomena were not observed at other nearby breeding sites, researchers analyzed this as an exceptional case caused by specific environmental factors.

Emperor penguin breeding grounds on Coulman Island and chick penguins presumed to have died of starvation. Provided by the Polar Research Institute

During a field survey last month, the research team confirmed that a giant iceberg, approximately 14 kilometers in length and covering an area equivalent to about 5,000 soccer fields, was blocking the main passage between the breeding grounds and the sea. Satellite data analysis revealed that this iceberg separated from the Nansen Ice Shelf in March, drifted northward, and blocked the entrance to the breeding site around the end of July.

Emperor penguins lay their eggs every June. After laying, the female goes to the sea to hunt for food while the male incubates the egg. Two to three months later, when the chick is about to hatch, the female returns to feed it. This year, however, the iceberg blocked the migration route, exposing many chicks to starvation. Drone footage showed dozens to hundreds of adult penguins unable to return to the breeding grounds due to the iceberg cliffs, as well as traces of excrement indicating prolonged stays.

Comparison of Emperor Penguin Habitats on Coulman Island from November 2024 to 2025. In 2025, compared to 2024, traces of guano, the excrement of emperor penguins (brown in the left photo), are barely visible. Provided by the Polar Research Institute.

Kim Junghoon, the lead researcher at the Korea Polar Research Institute, explained, "The surviving 30% of chicks appear to have been fed by mothers who found alternative routes not blocked by the iceberg. If the iceberg disappears before the next breeding season, recovery is possible. However, if it remains for an extended period, emperor penguins may relocate to other breeding sites, leading to long-term impacts."

Park Jingu, a researcher at the Korea Polar Research Institute who analyzed the satellite data, expressed concern: "The movement path of the iceberg that separated from the Nansen Ice Shelf is also passing near other major emperor penguin habitats. This case shows that the collapse of the ice shelf could pose a potential threat to emperor penguins and the Antarctic ecosystem as a whole."

Emperor penguin habitat on Coulman Island and location of the giant iceberg (left), movement path of the iceberg separated from the Nansen Ice Shelf (right). Provided by the Korea Polar Research Institute

The research team plans to officially report this case to international organizations such as the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) next year. The Ross Sea is the world's largest marine protected area, home to over a million Ad?lie penguins, tens of thousands of emperor penguins, as well as whales, seals, seabirds, and krill.

Since 2017, the Korea Polar Research Institute has been conducting the Ministry of Oceans and Fisheries' R&D project, "Study on Ecosystem Changes Following Implementation of Conservation Measures in the Ross Sea Marine Protected Area." By combining field surveys with remote sensing techniques such as satellite and aerial monitoring, the institute has been conducting long-term analyses of population changes in key species and environmental factors.

Shin Hyungchul, Director of the Korea Polar Research Institute, stated, "This incident demonstrates how climate change can bring unpredictable risks to the Antarctic ecosystem. We will strengthen satellite monitoring and field investigations through the next breeding season and continue to study the impact of climate change on the Antarctic ecosystem."