Where did all of those king penguins go?

It’s unclear what has happened to what was, even a few decades ago, the largest colony of king penguins

This is a picture of the largest colony of king penguins in 1982. It once hosted some 500,000 pairs of breeding birds each season. Recently discovered losses, though, are so big they could affect the species’ total population.

J.C. Stahl

Since the 1980s, what was once the king of king penguin colonies has lost 85 percent or more of these big birds. It’s a loss of perhaps one in every three of the species’ total population. That’s the finding of a new study.

The penguins live on a sub-Antarctic island in the southern Indian Ocean. It’s called Île aux Cochons (Isle of Pigs). And in its glory days, this island was home to the world’s largest colony of king penguins. Satellite data suggest that back in the 1980s, this island boasted 2 million penguins. Of these, some 500,000 were breeding pairs, says Henri Weimerskirch. He’s a seabird specialist based at the University of La Rochelle, in France, who works for CNRS. (That’s short for Centre National de la Recherche Scientifique. It is France’s national center for scientific research.)

The king penguin population peaked around that time. Since then, things have changed — a lot.

A 2015 satellite analysis showed only 77,000 pairs on the island. A 2016 helicopter survey came up with only 51,000 breeding pairs. Weimerskirch and colleagues shared this unsettling news in the August 2018 Antarctic Science.

The International Union for Conservation of Nature is based in Gland, Switzerland. It identifies species at risk of going extinct. This group has listed king penguins in a category of being least at risk of extinction. That listing may change, Weimerskirch says, “since the species has lost nearly one third of its population.”

King penguins are the second tallest penguins (after emperor penguins). The kings can densely pack themselves into a tight space at breeding time. About two penguins will fit into every square meter (11 square feet, or a square of about 3.3 feet on each side). The panorama of so many birds once was “breathtaking,” Weimerskirch recalls. The underlying ridges in the birds’ home created the illusion of waves in a sea of penguins.

Four other king penguin colonies have changed sizes in a different way. They shrank during tough weather in 1997, Weimerskirch notes. But then they recovered and became stable.  Whatever’s wrong on Île aux Cochons is probably specific to that island, he notes. Its penguins may not have been able to recover from threats such as a weather crisis, invasive cats, diseases or parasites. But that’s only a guess, as researchers haven’t checked out the penguins there in person since 1982. They will need a return visit, Weimerskirch says, if they hope to solve the mystery of the penguin population plunge.

a sattelite image of the Île aux Cochons showing the shrinking boundary of the penguin colony over time
This is a 2015 satellite image of Île aux Cochons in the southern Indian Ocean. The outlines show how what was once the largest king penguin colony has shrunk over the past three decades. Yellow shows the extent of the area occupied by breeding penguins in 1982. Blue (2005) and green (2015) lines show shrinkage of bare soil as plants regrow over penguin-free ground, as seen in this 2015 satellite image. H. Weimerskirch et al/Antarctic Science 2018

a sattelite map with an outline showing hte boundary of bare ground where penguins used to be
Bare ground is outlined in green in this satellite imagery from 2015. It’s the most recent year with a good view of Île aux Cochons. The orange outline shows that masses of breeding king penguins don’t even occupy all that space. H. Weimerskirch et al/Antarctic Science 2018

Susan Milius is the life sciences writer, covering organismal biology and evolution, and has a special passion for plants, fungi and invertebrates. She studied biology and English literature.

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