Pig Island (the Pig island) is a cold, lonely rock halfway between Madagascar and Antarctica. It is part of the French Southern Lands and, for decades, its 64 km2 of volcanic lands were the epicenter of the world’s largest king penguin colony.
However, in 2017 a series of satellite photographs set off all alarms: the island was “empty.” Almost 900,000 of these birds, 90% of the colony according to the available sources, they had disappeared without more. Something was happening and it didn’t look like anything good.
The problem is that going there was not exactly easy. It is not only that to find the last scientific expedition on the island you had to go back 37 years, but the isolation of the Crozet archipelago is so great that it requires mobilizing large amounts of resources (including ships, 700 kilos of equipment and even a helicopter ) for very short stays. Against all odds, Weimerskirch and Bost they got it started.
Five days at the end of the world
This was how a helicopter from the research ship ‘Marion Dufresne’ left these two French CNRS researchers and their team on the island in November 2019, in the middle of the nesting season of the king penguin. There was no time to lose: they had a maximum of five days to find out what had happened to the penguinsBut the region’s changing weather could force them to abandon everything in a matter of hours.
After verifying that, indeed, there were only a few thousand penguins left, the researchers installed traps, cameras and night vision systems to search for cats, rabbits and rats. These were the main suspects: unfortunately for island ecosystems, the arrival of ships to their shores can cause the introduction of predators that wreak havoc.
They found no signs of any of those animals. In fact, they found no injuries on the penguins that remained on the island, nor did they identify any marks on the bones they were able to unearth. Blood and feather tests they also found no disease or parasite that could explain the collapse of the avian population.
Another option to consider was that the penguins had simply moved to one of the “nearby” islands of the archipelago. However, their analyzes in situ and with satellite images they showed that, although some colonies had grown, they had only grown in 17,000 pairs. A clearly insufficient number to explain the mystery.
After giving it a lot of thought, the only plausible explanation was in the ocean. As part of the expedition, the researchers tagged several penguins with gps detectors. It has been known for years that this species is capable of moving more than 250 kilometers to feed. The problem is, these penguins seemed to be drifting even further away.
Researchers believe, the Île aux Cochons had become the king penguin capital of the world because it was relatively close to the “Antarctic convergence” line; the place where the cold waters of the Antarctic Ocean sink under the warm waters of the surrounding oceans. This area is especially rich in marine creatures (which penguins feed on).
That line of thermal contrast is not static. What’s more, it is constantly changing, but for centuries it was relatively stable at the distance that a king penguin can do without problems. According to French researchers, for decades that line has been increasingly south and that seems the most likely cause of the mystery: penguins cannot go back and forth to the convergence zone to feed.
There is still a lot to investigate, but it will take time to find out what happened. Despite the disappearance of all these animals, the royal penguin is one of the few species that is not endangered (What’s more, their figures are improving little by little). That limits efforts to understand situations like those on the Île aux Cochons. It is reasonable (taking into account the financial limitations that exist); However, it is good to be attentive to that region of the South Seas, as we can see there is still much to learn.
Imagen | Brian Mcmahon