King penguins thrive in a warmer climate, but it may not last

King penguins not only survive, but thrive as temperatures rise in the sub-Antarctic, and several of their young survive to maturity. Although the species looks like a winner in the face of climate change, some scientists fear that it may eventually lose access to important food sources and decline.

King penguins (Aptenodytes patagonicus) on Possession Island, a French territory midway between Antarctica and Madagascar, began nesting about 19 days earlier in 2023 than they did in 2000. Thanks to this longer nesting season, 62 percent of chicks now survive on average, up from 44 percent in 2000, according to research at the Gaël his col Sleague Center and Gaël Bardonific.

“With king penguins, we can see that there are super-rapid changes in the Southern Ocean that are good for them at the moment, but long-term we don’t really know,” says Bardon.

Pairs of king penguins, recognizable by the brilliant yellow-orange feathers on their necks, care for a single egg during the Australian summer, from which a fluffy brown chick hatches about two months later.

Parents leave chicks on their home island and swim hundreds of kilometers south to the polar front, an area where the mix of warm and cold currents brings up nutrients that boost plankton growth. The penguins catch small lanternfish that feed on plankton, and bring some fish back to the young.

Warmer water can increase the number of lanternfish. The study found that early breeding was mainly correlated with higher sea surface temperatures and lower plankton concentrations, a combination that suggests an abundance of lanternfish.

This earlier breeding gives the young more time to fatten up on fish before the long, hungry winter, so fewer of them starve, says Bardon.

Although better chick survival has not actually increased the population on Possession Island, which appears to have carrying capacity, it may be that more penguins move to other islands and grow the colonies there, he says.

At the same time, the king penguins’ shift towards past breeding, which has happened faster than in almost any other polar species, is an “alarm signal” that shows how quickly the environment is changing, according to team member Céline Le Bohec, also at the Monaco Scientific Center.

In previous years of unusual warmth, the polar front has retreated south and the king penguins have had to swim further to catch fish, leading to lower chick survival and a decline in the population on Possession Island. Because there are no islands further south where the penguins can move, they have had to expand their catch range, and a previous study found that this population would decline in the coming decades if the polar front continues to gradually shift south.

“This rapid change, which increases the window of the breeding cycle, is positive, but when the food availability at the polar front will be … too far away from the colony, it will collapse,” says Le Bohec. “You will reach a tipping point.”

Other researchers are more optimistic. Lewis Halsey of the University of Roehampton, UK, who saw the Penguins on Possession Island return after a mini-tsunami in 2004, points out that they also eat other food such as squid closer to the island. He says the population may shrink, but not die out. “I don’t see a collapse, as I see them as inherently very flexible.”

At best, scientists would have expected king penguin breeding to remain stable as they adapt to climate change, so the fact that it actually improved is a very positive sign, says Tom Hart of Oxford Brookes University, UK.

“This is good news and things can certainly change, but when we look at other penguins in particular, most of them as a whole family are in decline,” he says. – This is a rare victory.

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