Scientists say gentoo penguins are actually four species, including a new one hidden in plain sight
A new genetic study says gentoo penguins should be split into four species, including a newly described bird from the Kerguelen Islands.
Scientists say a penguin most people thought they knew has been hiding a major surprise in plain sight. New genetic research argues that gentoo penguins are not one species but four, including a newly described lineage from the Kerguelen Islands that could mark the first new penguin species discovered in more than 100 years. The birds look strikingly alike, which is part of why the split went unresolved for so long.
What happened is straightforward, even if the science behind it is not. Researchers say the bird long grouped under the single label gentoo penguin actually falls into four separate evolutionary lineages that are distinct enough to be treated as species.
Their proposed list includes the northern gentoo, Pygoscelis papua; the southern gentoo, P. ellsworthi; the eastern gentoo, P. taeniata; and the newly described southeastern gentoo, P. kerguelensis. The new one was identified on the Kerguelen Islands, also known as the Desolation Islands, a remote French territory in the southern Indian Ocean.
That matters because gentoo penguins live across a broad stretch of the Antarctic Peninsula and sub Antarctic islands, yet they can look almost identical at a glance. They share the familiar black and white colouring, orange beaks and white markings above the eyes. According to the study, though, the similarities on the outside mask much deeper differences in their genomes.
Why scientists revisited a familiar penguin
Researchers involved in the work said gentoo classification has been argued over for more than a century. The debate has centred on whether the birds should be treated as one species with local variation, or split more finely into multiple species or subspecies.
A 2020 study had already suggested dividing gentoo penguins into four species and described a South Georgia bird as Pygoscelis poncetii. But that proposal was not widely accepted. The new research keeps the four species idea while changing the place of the South Georgia gentoo. Instead of treating it as a separate species, the authors place it within the southern gentoo as a distinct subspecies.
To test the question more thoroughly, an international team involving researchers from Chile and the University of California, Berkeley sequenced the genomes of 64 gentoo penguins from 10 breeding colonies. The sampling covered nearly the birds' full geographic range. The team also compared physical measurements, colouring, vocalisations, breeding schedules, diets and feeding behaviour.
Taken together, those lines of evidence pointed in the same direction: the four groups have been evolving separately for a long time.
How one species stayed hidden in plain sight
The southeastern gentoo is the most striking part of the finding because it could represent the first discovery of a new penguin species in more than 100 years. The researchers also suggested that penguins on nearby Heard Island belong to the same lineage, although their genomic sampling was from Kerguelen rather than Heard Island.
The study estimates that the four lineages began splitting from one another roughly 300,000 to 500,000 years ago. Geography appears to be a big reason. The Antarctic Polar Front, a boundary in the Southern Ocean marked by sharp changes in temperature and salinity, can limit how marine animals move between regions.
The birds' own habits may have reinforced that separation. Gentoo penguins eat a wide range of prey, including fish, krill and squid, so they can rely on whatever is available locally instead of travelling far from breeding colonies. They also tend to return to the same nesting sites year after year. Over many generations, that mix of geographic isolation, limited movement and local environmental pressures could help separate populations genetically.
The genomes also offered clues about how different lineages may have adapted to different conditions. Southern gentoos showed signals linked to heat production, fat storage and light perception. Eastern gentoos showed signals tied to carbohydrate metabolism and processes associated with diving, including oxygen transport. Northern gentoos showed differences involving digestion, heart contraction and muscle activity. The researchers cautioned that those patterns do not prove one species is automatically a better diver or has a specific physical advantage over another.
Why the discovery comes with a warning
Beyond the naming debate, the study points to a conservation problem. If all gentoo penguins are counted as one wide ranging species, vulnerable island populations could be overlooked.
Using climate models, the researchers estimated where suitable habitat might still exist in 2050 under a moderate warming scenario. Their projections suggested that the three island dwelling species could lose suitable habitat across the islands they currently occupy, with few nearby alternatives. The southern gentoo, the only one of the four that lives in Antarctica, could be affected less severely and might even expand its range.
So this is more than a scientific rename. It suggests that birds which look very similar may be following very different evolutionary paths, and that some of those paths could be much more precarious than anyone realised when they were all treated as a single species.
