Provided by the Korea Polar Research Institute
The number of emperor penguin chicks in Antarctica has plummeted after a giant iceberg blocked their route. A research team from the Korea Polar Research Institute reported that the number of emperor penguin chicks on Coulman Island in the Ross Sea, Antarctica, dropped by 69% in just one year and suggested that a large iceberg blocking access to their breeding colony may have been the cause. The findings were published on July 23 in the international journal Communications Earth & Environment.
Coulman Island is the largest emperor penguin breeding colony in the Ross Sea. Since 2017, the research team has taken annual aerial photographs to monitor chick numbers. In a survey conducted in November 2025, they confirmed that the number of chicks had dropped sharply compared with previous years.
The number of chicks, which was about 21,000 in 2024, fell to 6,658 in 2025. To identify the cause, the researchers analyzed satellite imagery and found that a massive iceberg, stretching about 14 km, had drifted near the breeding colony by late July 2025.
This iceberg blocked the route of the mother penguins. After laying their eggs, female emperor penguins leave the eggs with the males and head to the ocean to hunt. They then return after two to three months, timed to the hatching of the chicks, to feed them. The iceberg drifted in just before hatching and blocked the mothers’ path.
As a result, the distance from the breeding colony to the sea is estimated to have increased from the previous 9.3 km to at least 14.9 km. Drone footage actually captured adult penguins unable to return to the colony because of the iceberg’s cliff-like edge, as well as chick carcasses within the breeding area.
The research team emphasized that, as ice shelves in Antarctica become increasingly unstable due to climate change, such incidental events must also be factored into conservation research on emperor penguins. However, they cautioned that because this study covers only a single breeding season, it is still too early to conclude that the iceberg’s grounding was the direct cause of the decline in chick numbers.
Even so, lead researcher Kim Jeong-hoon of the Korea Polar Research Institute said in an interview with Yonhap News Agency, “It is highly unusual for chick numbers to fall by 69% in a single year,” adding, “Fortunately, the iceberg has drifted away to another area, so we need to watch whether the population recovers during this year’s breeding season.”
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