Antarctic penguins breeding earlier due to climate change

(CN) — For millions of years, penguins ruled the Antarctic as their own ice haven, unbothered with the goings-on of the rest of the world. But the world — through climate change — is catching with them, and they are adapting their behavior as a result.

A new study published Tuesday in the Journal of Animal Ecology, timed with World Penguin Awareness Day, found that three penguin species have shifted their breeding seasons earlier by at least 10 days — and by nearly 24 days in some colonies — likely because of warming temperatures.

The researchers said the changes among Adélie, chinstrap and gentoo penguins could heighten competition for food between the species.

“Adapting to a changing climate is good only because the other option is worse,” lead author and University of Oxford researcher Ignacio Juarez Martínez told Courthouse News in an email.

“Adapting can still have consequences, like taking longer to find food or increased competition with other species that were not a problem before.”

He said researchers believe gentoos, which traditionally would breed later, are causing an overlap and increased competition among the three species for food and nesting space. They’ve already seen gentoos take over nests made by the other two.

Martínez and his team, including researchers with the citizen science project Penguin Watch, said gentoo penguins are likely to adapt best because they are less selective feeders, eating fish, crustaceans, krill, shrimp and cephalopods. Chinstraps rely more heavily on krill, while Adélies depend on sea ice for breeding and foraging.

The study analyzed data collected from 2012 to 2022 using cameras that tracked penguin “settlement,” defined as the first date a colony continuously occupied a nesting site on the Antarctic continent or sub-Antarctic islands.

Penguins typically start to settle between October and November, build their nest and mate, so their two eggs can be laid in late November or early December. Colony sizes range from a few dozen to hundreds of thousands of birds.

Over the decade, gentoo penguins showed the largest shift, advancing their breeding season by an average of 13 days — the fastest change in phenology, or the timing of natural events such as breeding and migration, ever recorded for a vertebrate, the researchers said.

The adaption may help the gentoos in the long term, along with their preference to live in more temperate areas of Antarctica. It is the species estimated to have the likeliest survival rate as temperatures rise.

“According to the current trends and the latest forecast models, chinstraps are the ones most at risk,” Martínez said. “It is likely that chinstraps are extinct from Antarctica before the end of the century. Adélies would be the next in line. They are probably going to be extinct from the West Antarctic Peninsula but will remain in other cold and sea-ice prone areas of the continent, like the Weddell Sea or East Antarctica.”

Changes in Antarctic sea ice are central to understanding how the flightless birds are adapting. The study used monitoring cameras equipped with thermometers, which showed colony sites warming up to four times faster than the Antarctic average, leading researchers to conclude the colonies are among the fastest-warming habitats on Earth.

In the past, Martínez said the penguins could adjust temperature changes, but the team found that may not be the case anymore.

“A shift of the distribution south to colder climates has always been the bet of scientists for cold-adapted penguins like Adélies, but now this feels more like an unfulfilled hope,” he said. “We are seeing Adélies decline in the peninsula, but we are not seeing them establish new colonies in colder areas, sadly.”

All three species are listed as “least concern” on the International Union for Conservation of Nature Red List of Threatened Species, but researchers warned that rising temperatures could affect more than just penguins’ breeding cycles.

“As penguins are considered ‘a bellwether of climate change,’ the results of this study have implications for species across the planet,” co-author and University of Oxford researcher Fiona Davis said in a statement.

“Further monitoring is needed to understand whether this record advance in the breeding seasons of these penguin species is impacting their breeding success.”