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The Rockhopper Penguin (Eudyptes chrysocome) is unusually classified. Some authorities classify it as a single species with three subspecies, others classify the Rockhopper Penguins into two or three separate but closely related species. The main differences between the three main populations of Rockhopper Penguins are the location of their breeding colonies and their reproductive behavior, which to some are enough to separate them into distinct species. For the purposes of this edition of Flightless Friday, the three subpopulations will be grouped together, with differences noted. All of the images used in this post show Southern Rockhopper Penguins.

Rockhopper Penguins are one of the smaller species, with adults standing only 20 inches (52 cm) tall, and weighing a maximum of 6.6 pounds (3 kg) depending on the season. Males are slightly larger than females, on average, but they are so close in size that often DNA testing is needed to determine the sex of a given penguin. Rockhopper Penguins have yellow crests over their red eyes, and when they reach adulthood their bills turn bright orange. Their feet are white on top and black on the bottom. The three populations are located as follows:

  • Eudyptes chrysocome or Eudyptes chrysocome chrysocome (The Falkland Islands and islands off the shore of Chile, Argentina. Considered to be the “true” Southern Rockhopper Penguin.)
  • Eudyptes fiholi or Eudyptes chrysocome fiholi (Sub-Antarctic islands like the Prince Edward Islands, Kerguelen Islands, Auckland and Antipodes. Known as the Eastern Rockhopper Penguin.)
  • Eudyptes moseleyi or Eudyptes chrysocome moseleyi (Islands of St. Paul and Manchester in the Indian Ocean, Tristan de Cunha and Gough in the Atlantic Ocean. Called the Northern Rockhopper Penguin.)

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The diet of Rockhopper Penguins depends on their specific range, but it consists primarily of krill, small crustaceans like crabs and lobster, cephalopods and small fish. Rockhopper Penguins can spend days at sea foraging for food, and regularly dive up to 328 feet (100 meters) to hunt. They are able to stay underwater for several minutes.

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Breeding colonies of Rockhopper Penguins can number in the hundreds of thousands. Once a breeding pair is formed, they remain monogamous and most often return to the same nesting site each year. Females will lay a clutch of two eggs sometime in November, and in most of the colonies the larger egg is the only one that hatches. But in the Falklands, the breeding pairs are often able to incubate both of them successfully, and end up raising two chicks. The incubation period lasts 33 days, with both parents taking it in shifts. Newly-hatched chicks are brooded for the first month before they join the crèche.

The breeding colonies of Rockhopper Penguins have started to drop off in numbers, with the breeding colony in the Falkland Islands declining by 90 percent in the last 60 years. The specific interaction of the threats facing the Rockhopper Penguins need further study, but at the moment it is believed that human activity, such as pollution, fishing and and even ecotourism is having a negative impact on the colonies. Rockhopper Penguins are also vulnerable to climate change.

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Source for all images used in this post.