Extract from ABC News
King penguins have the longest breeding cycle of any penguin species. (iNaturalist: admss, King penguin, CC-BY-NC 4.0)
In short:
King penguins on the Crozet Islands are breeding earlier and with a higher level of success than they did 24 years ago.
Researchers say this is likely in response to their changing environment and food availability.
Other penguins in the region are also bringing forward their mating cycles.
Climate change is putting pressure on many animals and their food chains at the extremes of our planet.
Animals that are higher up the food chain, such as penguins, are especially vulnerable to changes in the environment.
But research published today in Science Advances shows some penguin species are changing breeding habits in the face of climate change — and it appears to be working for them.
Researchers found king penguin (Aptenodytes patagonicus) populations on the sub-Antarctic archipelago of Crozet in the Southern Ocean were breeding 19 days earlier than 24 years ago, with greater success rates for chick survival.
Study co-author Robin Cristofari, an evolutionary biologist from the University of Helsinki, said the shift was an "unbelievably large change" in breeding dates, but warned the trend might not last.
"King penguins are very flexible and resilient animals, and importantly they are surfing on the 'good edge' of climate change for the moment."
How often do king penguins breed?
King penguins have distinctive orange patches on their head, neck and beak. (Wikimedia: Liam Quinn CC BY-SA 2.0)
King penguins are the second largest penguin species — they're just a bit smaller than the iconic emperor penguin.
They live in ice-free areas on sub-Antarctic region including the Crozet Islands, South Georgia Island, and Australian territories such as Heard Island, McDonald Islands, and Macquarie Island.
King penguins have the longest breeding cycle of any penguin species, lasting between 13 and 16 months.
To find the average start date for breeding in the Crozet colony, researchers monitored more than 17,000 penguins from the sub-species A.patagonicus halli for 24 years.
They used RFID microchips — similar to what's in anti-theft tags in shops — to find out when the penguins left to get food and when they returned to their breeding partner in the colony.
A king penguin chick hatching from its egg, Possession Island, Crozet Islands. (Supplied: Gaël Bardon)
Using a deep learning model, the researchers monitored the penguins' behaviour and worked backwards to estimate when the birds mated.
Twenty-four years ago, the average date was around November 27, with the date moving forward to November 8 by 2023.
For every day the mating event was brought earlier, there was about a 1 per cent increase in the success rate of breeding.
The breeding success of the penguins in 2000 was 44 per cent, and reached 62 per cent in 2023.
Why are penguins breeding earlier?
It was unclear how the penguins knew when to breed earlier.
Dr Cristofari said it was probably a combination of factors that included long-term processes that increased food availability, and the short-term cues that helped the animals sense when spring was coming.
"One element is probably that king penguins breed when they feel strong and healthy, and when the weather gets them in the mood,"he said.
Improved weather conditions may also allow the penguins to breed sooner, according to Céline Le Bohec, another study co-author and seabird ecologist at the Centre Scientifique de Monaco.
"When adults can regain energy more quickly, they may be able to start the next breeding attempt sooner, effectively extending the breeding window," Dr Le Bohec said.
The king penguin colony of Cap Ratmanoff, one of the largest king penguin colonies in the world, Kerguelen Islands. (Supplied: Céline Le Bohec)
Breeding success — a chick making it to adulthood — is also based upon the availability of food.
King penguins, which mainly eat lantern fish and squid, must feed themselves and their young enough to have sufficient body mass to survive the harsh winter.
"As you can imagine, having three more weeks to put on fat before a full winter of fasting is a huge advantage. And if that next summer actually comes three weeks earlier too, then it's a double advantage," Dr Cristofari said.
The study found the earlier onset of breeding and the success of it were related to increased sea surface temperatures and ocean productivity (which is a measure of the availability of food).
It's not entirely understood why the two factors are related, but Ignacio Juarez Martinez, a penguinologist at Oxford University who was not involved with the research, suggested that warmer conditions could create more of the bacteria and algae for the fish that the penguins eat.
"It could be that currents have changed and brought up more nutrients from the bottom of the ocean, that algae bloom earlier and better in warmer waters," Dr Juarez Martinez said.
"Or that some species that would compete with penguins have disappeared and the penguins have more food now," he added.
King penguins back from their foraging trip, Possession Island, Crozet Archipelago. (Supplied: Céline Le Bohec)
Gaël Bardon, lead author on the study and seabird ecologist at the Centre Scientifique de Monaco, said the long breeding period also allowed king penguins to be more resilient in the face of environmental changes.
"This flexibility can help populations buffer against environmental variability, such as years with poor food conditions or storms," Dr Bardon said.
But the penguins can't keep breeding earlier and earlier.
"Climate change or not, winters will always be darker, with less photosynthesis and less marine productivity," Dr Cristofari said.
Continued environmental change may lead to seasonal mismatches between predators and prey across the food chain, which can threaten penguins, their prey, and the entire ecosystem.
Earlier breeding a trend in many penguins
While the study only looked at king penguins in the Crozet Islands, Dr Cristofari said the breeding patterns of king penguins on other sub-Antarctic islands was also likely to be changing.
"I wouldn't be surprised if king penguins [on Australian sub Antarctic islands] soon followed suit," Dr Cristofari said.
"I think what we're observing is really coming together as a global trend."
The breeding patterns of other species of penguins on other islands and parts of Antarctica are also shifting, albeit not as fast, according to recent research by Dr Juarez Martinez and colleagues.
"Spelled differently... how much time do we have until even the penguins that are adapting to climate change start suffering from it?" he said.
Dr Le Bohec said it was important to keep looking at these breeding habits, as it showed how things were changing before populations begin to decline.
"Overall, the long-term outlook will depend on how well penguins can track shifting prey resources in a rapidly warming Southern Ocean," she said.
In addition to climate change, there are other threats to penguins in the sub-Antarctic region such as the H5N1 strain of bird flu.
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