A remote island near Antarctica is no longer home to the world's largest penguin colony as climate-driven changes to ocean food chains likely devastated its once-thriving inhabitants and caused a "population collapse," researchers said Wednesday. Drone and satellite images showed that the volcanic island of Zavodovski lost more than 680,000 — or nearly two-thirds — of its chinstrap penguins between 2011 and 2025, according to the British Antarctic Survey (BAS). "That's a very rapid loss," Norman Ratcliffe, the lead author of the BAS study published in the journal Current Biology, told AFP.
The study's findings raise concerns that chinstrap populations across the South Sandwich Islands, which include Zavodovski and are home to 38% of the species, have fallen. The scientists, who released video of their research, suggest that the "alarming declines" should lead to chinstrap penguins being redesignated as "endangered" by the International Union for Conservation of Nature (IUCN). This would be a sharp downgrade from their "least concern" classification, which means they are not currently threatened with extinction.
Surveys in 2011 had concluded that chinstrap populations across the South Sandwich Islands were stable. But their number on Zavodovski fell from around 1.09 million breeding individuals in January 2011 to 402,000 in 2025, or a 63% decline, according to the study. The island is also home to a different species, macaroni penguins, whose population rose from around 338,000 in 2011 to 433,000 in 2025 -- and now outnumber chinstraps.
Together, chinstraps and macaronis now total more than 835,000 on Zavodovski. The researchers said the Adelie penguins of Cape Adare, on the other side of Antarctica, are now the world's largest penguin colony, numbering more than one million as of 2018. Zavodovski island's Mount Curry volcano erupted in 2016, sparking fears that it could wipe out its penguin population.
But the researchers found that the ash cloud was blown northeast over an area not inhabited by the flightless birds. "The decline in chinstrap colony area was in progress prior to the eruption and continued at a constant rate thereafter," the study said. "We don't think the volcano is implicated or it's not the main driver (of the population decline) because what we see is a linear decline in the chinstrap penguins," Ratcliffe told AFP.
Instead, the scientists linked the drop in chinstrap numbers to a reduction in the availability of krill -- the tiny shrimp-like creatures that are their main food source. Warming ocean temperatures have pushed the crustaceans south toward colder waters, which chinstraps do not tolerate. "We think that climate change operating through food webs is probably the main driver," Ratcliffe said.
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