Zavodovski Island has lost its status as the world’s largest penguin colony after a sharp decline in its chinstrap penguin population, with researchers linking the fall primarily to climate-driven changes in the surrounding marine ecosystem. A study by the British Antarctic Survey found that the island lost more than 680,000 chinstrap penguins between 2011 and 2025, representing a decline of about 63 per cent.

The number of breeding chinstrap penguins on the remote volcanic island fell from around 1.09 million in 2011 to approximately 402,000 in 2025. Researchers used drone surveys, satellite imagery and other observations to track the long-term change. The findings have raised concerns about wider declines among chinstrap penguins across the South Sandwich Islands, which are estimated to contain a significant share of the species’ population.

Scientists believe the main factor behind the decline is the reduced availability of Antarctic krill, a key food source for chinstrap penguins. Rising ocean temperatures are pushing krill towards colder waters farther south, making them less accessible to the penguins. Researchers said the chinstrap population on Zavodovski has been declining by about seven per cent annually, pointing to a sustained environmental change rather than a sudden local event.

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The island experienced a volcanic eruption in 2016, initially raising concerns that ash and volcanic activity may have caused the penguin losses. However, researchers found that the decline had already begun before the eruption and continued at a broadly consistent rate afterward. The ash cloud also moved towards an area that was not occupied by the penguins, making the eruption an unlikely primary cause of the population collapse.

While chinstrap numbers have fallen, the island’s macaroni penguin population increased from about 338,000 in 2011 to roughly 433,000 in 2025. Researchers believe their broader diet may have helped them adapt better to changing food availability. Even so, the increase has not compensated for the sharp decline in chinstraps, and the island’s total penguin community has undergone a major shift in composition.

The findings have prompted researchers to urge a reassessment of the conservation status of chinstrap penguins. The species is currently classified as “least concern” by the International Union for Conservation of Nature, but scientists believe the rapid decline could justify an endangered classification. With Cape Adare in Antarctica now considered the site of the world’s largest penguin colony, the Zavodovski study has highlighted how climate-driven changes can affect even some of the planet’s most remote ecosystems.

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