World's Largest Penguin Colony Plummets by Nearly 63%

The chinstrap penguin colony on Antarctica's remote Zavodovski Island, once the largest in the world, has experienced a drastic population collapse, losing nearly 63% of its numbers since 2011. British Antarctic Survey (BAS) research indicates that the colony has dwindled from approximately 1.09 million breeding individuals to just 402,000 in 2025, a decline that occurred at a rapid annual rate of 7%.

This significant population drop means Zavodovski Island has lost its status as Earth's largest penguin colony. The title now passes to the Adélie penguin colony at Cape Adare on the opposite side of Antarctica, which was estimated to have over one million birds in 2018.

Researchers attribute the severe decline in chinstrap penguins to human-driven climate change, which is altering Antarctic food webs. Winter temperatures around the Antarctic Peninsula have risen by 5°C above pre-industrial levels, among the fastest warming rates globally. According to lead study author Norman Ratcliffe, climate change's impact on food availability is the most probable cause.

Rising ocean temperatures are pushing Antarctic krill, the chinstraps' main food source, into colder waters further south, beyond the penguins' tolerance. This forces the birds into a difficult choice: follow their food into less suitable habitats or stay and risk starvation.

While the chinstrap population has plummeted, the local macaroni penguin population on Zavodovski Island has increased, growing from roughly 338,000 breeding individuals in 2011 to 433,000 in 2025. This difference in population trends suggests that the warming waters have had disparate effects on the two species.

BAS researchers used drones to survey the colony and noted that the scale of the decline could lead chinstrap penguins to be classified as an endangered species. Zavodovski Island, located in the South Sandwich Islands, historically hosted 38% of the global chinstrap population.

Scientists have ruled out volcanic activity as the primary cause of the decline. Despite an eruption of Mount Curry in 2016, evidence suggests the ash cloud primarily moved away from the nesting grounds. The continued linear decline of the chinstrap population before and after the eruption further supports the conclusion that the volcano was not the main driver.