King penguins numbering 2 million that walk up to 40km inland to breed - the largest penguin gathering on Earth.
A City of Two Million
On Île aux Cochons, or Pig Island, in the remote Crozet Archipelago, is one of the planet's most incredible wildlife spectacles. This is the site of the world's largest colony of king penguins (Aptenodytes patagonicus), a gathering so vast it was once estimated to contain 500,000 breeding pairs and over two million individuals in total. The penguins occupy vast stretches of flat land, choosing beaches, valleys, and moraines free of snow and ice, sometimes trekking over a kilometer inland to find suitable breeding ground.
The king penguin's breeding cycle is one of the longest of any bird, lasting between 14 and 16 months from egg-laying to a fledgling chick. This means a successful pair can typically only raise a chick once every two to three years. After courtship, a female lays a single greenish-white egg, which both parents take turns incubating on their feet for about 55 days, under a warm fold of skin called a brood pouch. Once hatched, chicks are covered in a thin layer of down and are completely dependent on their parents. After about 40 days, they are large enough to join other chicks in a "crèche," a dense huddle that provides warmth and protection from predators like giant petrels and skuas while both parents forage at sea.
A Colony in Crisis
For decades, the Île aux Cochons colony was abundant. Scientists using high-resolution satellite imagery made a startling discovery. Between 1982 and 2017, the colony suffered a catastrophic decline of nearly 90%, shrinking from half a million breeding pairs to just 60,000. The total number of penguins on the island fell from two million to around 200,000.
The exact cause of this massive collapse remains a mystery and is ongoing research. One leading hypothesis points to a major El Niño event in 1997, which warmed the southern Indian Ocean and may have pushed the penguins' primary food source—lanternfish and squid—further south, out of their efficient foraging range. While other regional colonies were also affected, they eventually recovered; the Île aux Cochons colony did not. Its immense size may have worked against it, with intense competition for dwindling resources amplifying the effects of the food shortage. Other potential factors, such as disease or predation, are also being considered, but the remoteness of the island makes direct study difficult.
Beyond the famous king penguins, the Crozet Islands are a habitat for other species, including two million pairs of Macaroni penguins, 150,000 pairs of Eastern Rockhopper penguins, and 5,000 pairs of Gentoo penguins.
💡Fun Facts
King penguin chicks are covered in thick, brown, fluffy down, which led early explorers to mistake them for a separate species they called "woolly penguins."
To find food, king penguins are exceptional divers, repeatedly plunging to depths of over 100 meters (330 ft); the maximum recorded dive is 343 meters.
Their diet consists of about 80% fish, primarily bioluminescent lanternfish, which they hunt during the day.
Fidelity between breeding seasons is low, with less than 30% of pairs remaining together, likely due to the prolonged 14-16 month breeding cycle.
Not open to the public. Access to the Crozet Islands is strictly limited to personnel involved in scientific research missions.
Admission
Not applicable.
Accessibility
The islands are extremely remote, with rough volcanic terrain and no tourist facilities. The only way to reach them is via the French research and supply vessel, the *Marion Dufresne II*.