Warmer temperatures are forcing some Antarctic penguins to give birth earlier, study finds

Hotter temperatures are forcing Antarctic penguins to give birth earlier, creating a major problem for two beautiful tuxedoed species facing extinction by the end of this century, a study says.

Three different penguin species — the cartoon-eyed Adelie, the black-striped chinstrap and the fast-swimming gentoo — begin their reproductive process about two weeks earlier than a decade earlier, according to research published Tuesday in the Journal of Animal Ecology. Changing habits create potential feeding problems for chicks.

Researchers used remote-controlled cameras to capture penguins nesting in dozens of colonies from 2011 to 2021. Between 2012 and 2022, temperatures in breeding grounds increased by 5.4 degrees Fahrenheit.

“Penguins change their breeding season very quickly, 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 you give birth needs to coincide with the time when there are more resources in nature and this is the food for your chicks so they have enough to grow.”

The researchers say it’s the fastest change in the length of life cycles of any vertebrate they’ve ever seen. For a specific perspective, scientists have explored changes in the life cycle of the great tits, a European bird. They found the same two-week change, but that took 75 years compared to just 10 years for the three penguin species, said study co-author Fiona Suttle, another Oxford biologist.

Winners and losers in a warm country

Suttle said climate change is creating winners and losers among the three penguin species, at a time in the penguins’ life cycle when food and competition are critical to survival.

Adelie penguins and chinstraps are specialists, eating mainly krill. The gentoo has a varied diet. The birds used to breed at different times, so there was no overlap. But the breeding of gentoos has moved faster than the other two species, creating competition. That’s a problem because gentoos, which don’t migrate until the other two species, are very aggressive in finding food and establishing nesting sites, Martinez and Suttle said.

Suttle said he had gone back in October and November to the same places where he used to see Adelies in previous years only to find their nests replaced by gentoos. And the data backs up what he saw, he said.

“Chinstraps are in decline around the world,” Martinez said. “Models show that they could become extinct before the end of the century at this rate. Adelies are doing very badly on the Antarctic Peninsula and there is a good chance that they will become extinct on the Antarctic Peninsula before the end of this century.”

Other factors threaten the penguin population

Martinez hypothesizes that the warming of the west Antarctic – the second hottest place on Earth after only the Arctic North Atlantic – means less sea ice. Shrinking sea ice means more spores come out in the early Antarctic spring and you have “this amazing bloom of phytoplankton,” which is the basis of the food chain that eventually leads to the penguins, he said. And it happened at the beginning of the year.

Not only do chinstraps and Adelies have more competition for food from gentoos because of warming and changes in plankton and krill, but the changes have brought more priority fishing and that is shortening the penguins’ supply, Suttle said.

This shift in breeding time “is an interesting sign of change and now it is important to continue to look at these penguin species to see if these changes have a negative effect on their population,” said Michelle LaRue, a professor of marine science in Antarctica at the University of Canterbury in New Zealand. He was not part of the Oxford course.

With millions of photos – taken every hour by 77 cameras for 10 years – scientists are enlisting people every day to help mark breeding activity using the Penguin Watch website.

“We’ve had over 9 million of our photos annotated with Penguin Watch,” Suttle said. “A lot of that comes down to the fact that people love penguins so much. They’re so cute. They’re on every Christmas card. People say, ‘Oh, they look like little guards in tuxedos.’

Some penguin species in Antarctica are facing a crisis. Researchers from the British Antarctic Survey and the University of Southampton said last June that the number of emperor penguins on the continent may decline faster than the most pessimistic forecasts. The images showed the species, characterized by its length and yellow spots, declined in Antarctica by 22% between 2009 and 2024.