World’s largest penguin colony loses two-thirds of population since 2011

The world’s largest colony of chinstrap penguins has lost around two-thirds of its population since 2011, with scientists pointing to climate disruption as the most likely cause, according to a study published in Current Biology.

The decline on Zavodovski Island, the northernmost of the South Sandwich Islands in Antarctica, represents the loss of roughly 500,000 breeding penguins, according to Prof Norman Ratcliffe, a penguin ecologist at the British Antarctic Survey and leader of the research.

“It is an enormous population crash, equivalent to half a million breeding individuals being lost from that island,” he told The Guardian.

Ratcliffe said the loss of chinstrap penguins would have wider repercussions for food webs. 

“Each ecosystem could be regarded as like a giant Jenga set, and every component that you remove increases the risk of ecosystems collapsing completely.” 

Zavodovski was home to about 600,000 chinstrap penguins and 90,000 macaroni penguins when its population was measured in 2011. 

By 2025, the chinstrap population had fallen by about two-thirds, meaning the island may no longer hold the title of the world’s largest penguin colony.

Cape Adare in the Ross Sea is now likely to have the largest colony.

Researchers believe climate change is the most likely explanation for the sharp decline. 

Rising temperatures are altering conditions in Antarctic waters and affecting the availability of the food on which chinstrap penguins depend.

Chinstraps have a relatively specialised diet and favour cooler waters around Zavodovski. Tracking data indicates that the penguins typically forage to the island’s north-west, where Antarctic krill, their main food source, can be found.

As ocean temperatures rise, however, krill have shifted south towards the Weddell Sea, making it harder for the penguins to access their preferred food.

Macaroni penguins on Zavodovski have fared better. Their population increased by about 30%, although the growth was nowhere near enough to offset the decline in chinstraps.

Ratcliffe warned that the continuing loss of suitable habitat could eventually put pressure on all penguin populations on the island.

The study’s findings suggest the decline may be accelerating, raising concerns about whether chinstrap penguins could eventually meet the criteria for classification as an endangered species.