Gentoo penguins nest at Neko Harbour in Antarctica, Nov. 22, 2025. Mark Baker/AP

Warming temperatures are forcing Antarctic penguins to breed earlier, posing a big problem for two of the cute tuxedoed species that face extinction by the end of the century, a study says.

Three different penguin species — the cartoon-eye Adelie, the black-striped chinstrap and the fast-swimming gentoo — are beginning their reproductive process about two weeks earlier than the decade before, according to a study published Tuesday in the Journal of Animal Ecology. The change in habits is setting up potential food problems for young chicks.

Researchers used remote control cameras to photograph penguins breeding in dozens of colonies from 2011 to 2021. Between 2012 and 2022, temperatures in the breeding grounds increased by 5.4 degrees Fahrenheit.

"Penguins are changing the time at which they're breeding at a record speed, faster than any other vertebrate," said lead study author Ignacio Juarez Martinez, a biologist at Oxford University in the United Kingdom. "And this is important because the time at which you breed needs to coincide with the time with most resources in the environment and this is mostly food for your chicks so they have enough to grow."

The researchers said it was the fastest shift in timing of life cycles for any backboned animals that they have seen. For some perspective, scientists have studied changes in the life cycle of great tits, a European bird. They found a similar two-week change, but that took 75 years as opposed to just 10 years for these three penguin species, said study co-author Fiona Suttle, another Oxford biologist.

Suttle said climate change is creating winners and losers among these three penguin species, at a time in the penguin life cycle where food and the competition for it are critical for survival.

The Adelie and chinstrap penguins are specialists, eating mainly krill. The gentoo have a more varied diet. The birds used to breed at different times, so there were no overlaps. But the gentoos' breeding has moved earlier faster than the other two species, creating competition. That's a problem because gentoos, which don't migrate as far as the other two species, are more aggressive in finding food and establishing nesting areas, Martinez and Suttle said.

Suttle said she has gone back in October and November to the same colony areas where she used to see Adelies in previous years only to find their nests replaced by gentoos. And the data backs up her observations, she said.

"Chinstraps are declining globally," Martinez said. "Models show that they might get extinct before the end of the century at this rate. Adelies are doing very poorly in the Antarctic Peninsula and it's very likely that they go extinct from the Antarctic Peninsula before the end of the century."

Martinez theorized that the warming western Antarctic — the second-fasting heating place on Earth behind only the Arctic North Atlantic — means less sea ice. Less sea ice means more spores coming out earlier in the Antarctic spring and then "you have this incredible bloom of phytoplankton," which is the basis of the food chain that eventually leads to penguins, he said. And it's happening earlier each year.

Not only do the chinstraps and Adelies have more competition for food from gentoos because of the warming and changes in plankton and krill, but the changes have brought more commercial fishing that comes earlier and that further shortens the supply for the penguins, Suttle said.

This shift in breeding timing "is an interesting signal of change and now it's important to continue observing these penguin populations to see if these changes have negative impacts on their populations," said Michelle LaRue, a professor of Antarctic marine science at the University of Canterbury in New Zealand. She was not part of the Oxford study.

With millions of photos — taken every hour by 77 cameras for 10 years — scientists enlisted everyday people to help tag breeding activity using the Penguin Watch website.

"We've had over 9 million of our images annotated via Penguin Watch," Suttle said. "A lot of that does come down to the fact that people just love penguins so much. They're very cute. They're on all the Christmas cards. People say, 'Oh, they look like little waiters in tuxedos.'"

Other penguin species in Antarctica are facing trouble. Researchers from the British Antarctic Survey and University of Southampton said last June that the continent's emperor penguin population may be declining faster than even the most pessimistic predictions. Images showed the species, recognizable by their height and yellow patches, declined in Antarctica by 22% between 2009 and 2024.

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