Warming in Antarctica is forcing three species of penguins to start breeding earlier than they did in the preceding decade, a study published in Journal of Animal Ecology said. The researchers reported that temperatures in the Antarctic breeding ground rose by 5.4 degrees Fahrenheit (3 degrees Celsius) from 2012 to 2022, and that breeding began about two weeks earlier than the timing seen in the prior decade. The report described the shift as a major problem because it can disrupt food availability for chicks.
Lead author Ignacio Juarez Martinez, a biologist at Oxford University, said penguins are changing their breeding timing “at a record speed, faster than any other vertebrate,” adding that breeding time has to coincide with when most environmental resources are available for chicks to grow. He also pointed to how the timing shift could affect survival when food and breeding schedules stop matching.
Co-author Fiona Suttle said scientists have observed a similar two-week life-cycle change in great tits, but that it took 75 years in that case rather than 10 years for the three penguin species studied. In the Antarctic work, researchers used remote control cameras to photograph penguins breeding in dozens of colonies from 2011 to 2021, according to the report.
The study focused on three brush-tailed species—Adelie, chinstrap and gentoo—named for having tails that drag on ice. The researchers said the shift toward earlier breeding happened across all three species, and described it as the fastest change in life-cycle timing for backboned animals they have seen.
Suttle said climate change is creating winners and losers among the species, particularly at a point in the penguin life cycle where access to food and competition are critical. She described the Adelie and chinstrap penguins as specialists that eat mainly krill, while gentoo have a more varied diet. The study said gentoo once bred at different times, limiting overlap with the other two species, but that gentoo breeding has moved earlier faster than the other species.
The report said overlap is problematic because gentoo can be more aggressive in finding food and establishing nesting areas. It also said gentoo don’t migrate as far as the other two species, which can put them in a stronger position to take advantage of the altered timing. Suttle said she returned in October and November to colony areas where Adelies had previously nested and found the nests replaced by gentoos, and that the data supported the changes she observed.
Martinez said chinstraps are declining globally and that models suggest they might reach extinction before the end of the century at the current pace. He also said Adelies are doing very poorly in the Antarctic Peninsula and that it is very likely they will go extinct there before the end of the century.
The study’s explanation for the timing shift includes changes to sea ice and food-chain timing. Martinez theorized that warming in the western Antarctic—described in the report as the second-fasting heating area on Earth after the Arctic North Atlantic—reduces sea ice, which can mean spores come out earlier in the Antarctic spring and triggers “an incredible bloom of phytoplankton” earlier each year. He said the bloom supports the food chain that eventually feeds penguins and that the earlier feeding window can arrive at a different time than when penguins breed.
Suttle said the breeding shift is also affecting food availability through ecosystem and human activity changes. She said the changes in plankton and krill and the earlier timing have brought more commercial fishing earlier, which further shortens the food supply for penguins.
In commentary on the work, Michelle LaRue, a professor of Antarctic marine science at the University of Canterbury in New Zealand who was not part of the Oxford study, said the breeding shift is an “interesting signal of change” and that continued observing is needed to determine whether the timing changes have negative impacts on penguin populations.
The researchers also used a citizen-science component. With millions of photos taken over the study period—described as images captured every hour by cameras across 10 years—people helped tag breeding activity through the Penguin Watch website. Suttle said researchers had over 9 million images annotated via Penguin Watch, and she attributed much of that participation to the fact that people “just love penguins so much,” noting that penguins appear on Christmas cards and are widely recognized.
Suttle added that public interest could also connect to the species’ visual appeal, saying about Adelies that there’s “perhaps a kind of cheekiness about them — and this very cartoon-like eye that does look like it’s just been drawn on.”