World’s largest penguin colony loses nearly two-thirds of population amid climate change: Study

A remote island near Antarctica that was home to the world's largest penguin colony has lost nearly two-thirds of its chinstrap penguin population since 2011, according to a new study published Wednesday.

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

The population declined from an estimated 1.09 million breeding individuals in 2011 to about 402,000 in 2025, representing a loss of more than 680,000 penguins.

Researchers used drone surveys, aerial photography, satellite data and tracking devices fitted to penguins to assess changes in the colony.

They found that the decline was linked to climate-driven changes in the Southern Ocean affecting the availability of Antarctic krill, the main food source for chinstrap penguins.

"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 BAS 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 global population of the species.

Researchers said the scale and speed of the decline could also support reassessing the chinstrap penguin's conservation status, which is currently listed as "Least Concern" by the International Union for Conservation of Nature.