World’s largest chinstrap penguin colony loses 63% of its population

The world’s largest chinstrap penguin colony has lost nearly two-thirds of its population since 2011, according to a study published Wednesday.

Researchers led by the British Antarctic Survey found that the number of chinstrap penguins on Zavodovski Island in the South Sandwich Islands declined by 63% between 2011 and 2025.

The colony’s estimated breeding population fell from 1.09 million in 2011 to about 402,000 in 2025, a loss of more than 680,000 penguins.

To assess the changes, researchers used drone surveys, aerial photography, satellite data and tracking devices fitted to penguins.

The study linked the decline to climate-driven changes in the Southern Ocean that affect the availability of Antarctic krill, the penguins’ main food source.

“Our tracking data shows they prefer to forage in cooler waters to the northwest of the island, where they would expect to find Antarctic krill – the prey that make up the bulk of their diet,” said Norman Ratcliffe, a penguin ecologist at the British Antarctic Survey who led the research.

The findings raise concerns about chinstrap penguins across the wider South Sandwich Islands, which are home to a significant share of the species’ global population.

Researchers said the scale and speed of the decline could also prompt a reassessment of the species’ conservation status. The International Union for Conservation of Nature currently lists chinstrap penguins as “Least Concern”.