World's largest penguin colony loses 63% of its Penguins; scientists say climate change is to blame, not volcano

A remote volcanic island near Antarctica, once known for hosting the world's largest penguin colony, has suffered a major decline in its chinstrap penguin population. The island of Zavodovski in the South Sandwich Islands has lost nearly two-thirds of its breeding chinstrap penguins in just 14 years, according to a new study. Researchers found that the number of occupied chinstrap penguin nests fell by 63% between 2011 and 2025. Interestingly, scientists say the island's active volcano is not responsible for the decline. Instead, warming ocean waters and changes in the penguins' food supply appear to be the bigger problem.

Zavodovski Island loses more than half a million chinstrap penguins

Researchers from the British Antarctic Survey (BAS) compared satellite images, drone photographs and aerial surveys to study the penguin population. In 2011, the island had around 542,675 occupied chinstrap penguin nests. By January 2025, that number had dropped to 201,182. Since each nest represents a breeding pair, the figures show a sharp fall in the island's breeding population.

The decline has also cost Zavodovski its title as the world's largest penguin colony. That position now belongs to the Adélie penguin colony at Cape Adare in Antarctica's Ross Sea. According to Sky News, researchers described the fall as a "huge collapse". The team also found large areas of empty nesting ground where penguins had previously bred.

Why is the chinstrap penguin population declining?

Scientists believe climate change is affecting the availability of Antarctic krill, a small shrimp-like creature that makes up much of the chinstrap penguin's diet. As ocean temperatures rise, krill have moved southwards towards the Weddell Sea in search of colder waters. This has made it harder for chinstrap penguins to find food in their usual feeding areas.

Professor Norman Ratcliffe, the BAS penguin ecologist who led the study, said: "The problem is, with waters warming, the krill have moved southwards into the Weddell Sea." Euronews reported that chinstrap penguins prefer cooler waters and have a specialised diet, making them more vulnerable to these changes.

Why is the volcano not responsible?

Zavodovski is home to Mount Curry, an active volcano that erupted in March 2016, covering parts of the island with smoke and ash. However, researchers found that the penguin population had already been declining before the eruption. The fall also continued at a similar pace afterwards, suggesting that the volcanic activity was not the main cause. Scientists also examined other possible reasons, including competition between penguin species and nearby krill fishing, but found no strong evidence that these factors explained the decline.

Macaroni penguins are increasing on the island

While chinstrap penguins are disappearing, macaroni penguins appear to be doing better. Their population increased by around 28% between 2011 and 2016 and has remained stable since. Researchers recorded 216,606 macaroni penguin nests in 2025. Unlike chinstrap penguins, macaroni penguins have a more varied diet. They can eat fish and other crustaceans when krill becomes harder to find. The researchers described the change in the island's penguin population as the biggest shift in community composition recorded at a single location in Antarctica.