Gentoo penguins are four distinct species, not one, new study suggests

Ten years ago, as Dr Jane Younger started analysing data for her PhD, something struck her as odd.

In front of her were the DNA results for five different species of penguin found across Antarctica and the Southern Ocean.

The genetic data for emperor, king, chinstrap, and Adelie penguins were as expected, with no major variations, even for populations located thousands of kilometres apart.

But it was a different story for gentoo penguins.

"Gentoos just had so much difference in their genomes between these different islands that it was orders of magnitude more different than what you would see in another species," Dr Younger said.

The results got her thinking.

Could gentoo penguins from different regions be not just one standalone species, but multiple species that all look very similar?

Fast forward a decade, and Dr Younger has now co-authored a paper in Nature's Communications Biology journal that suggests that is indeed the case.

"The main finding is gentoo penguins are not one species — they're actually four," the vertebrate ecologist from the Institute for Marine and Antarctic Studies at UTAS said.

'It just felt so obvious'

But proving the hypothesis has taken years of work, as well as lots of travel.

After her initial DNA study in 2016, Dr Younger turned her attention in 2020 to penguin collections held in international museums.

"I went to France and the UK and the United States and measured all the gentoo specimens that I could get my hands on to try to see if they were actually physically different from each other," she said.

Two years later, she led an expedition to the Falkland Islands, South Georgia, and the Antarctic Peninsula, where her team caught gentoos to collect blood samples.

"In the Falklands … [they are] just so much bigger," she said.

"And then when we got onto the peninsula, they're so much smaller, they're easier to handle.

"It just felt so obvious that they're different species, but you would need to have that comparison of having them in your hands to be able to tell."

The new study puts forward the case for four unique species:

The southern gentoo on the Antarctic Peninsula and South Georgia

The northern gentoo located in parts of South America and the Falkland Islands

The eastern gentoo on Macquarie Island, as well as Crozet and Marion Islands

The southeastern gentoo on Kerguelen Island

The study, which was peer reviewed, used a combination of evidence, including whole-genome data, morphology, ecological modelling and evolutionary analyses.

But it still has another hurdle to pass.

"So, it now goes to taxonomic committees who will review this and see if they think that the claim is valid."

Conservation push for at-risk penguins

Dr Young said recognition of gentoo penguins as four distinct species could have significant conservation benefits because each type is faring differently.

On the Antarctic peninsula, which has been subject of rapid climate warming, the southern gentoo is doing very well.

"What used to be full of ice is now like [an] ice-free habitat that's actually suitable for gentoos to nest," she said.

"As we've lost ice through there, we're seeing gentoos spreading further south every year and new colonies of this species popping up and the numbers growing."

But on the Falkland Islands, the northern gentoo has been decimated by the arrival of bird flu.

And on Macquarie Island, Dr Younger said the eastern gentoo population had dropped by about 50 per cent over the past 20 years.

"And we don't actually know why that's happened, but they definitely are not doing well in the same way that they are on the Antarctic Peninsula."

Gentoos are currently categorised as being of "least concern" on the IUCN Red List of Threatened Species.

But Dr Younger said some of the gentoos that are faring poorly could be considered "endangered" if they were recognised as distinct species.

She said recognition could lead to better conservation management plans for those most at risk.

"I feel like it's easy to think that taxonomy is just like an academic thing that's just about assigning names to stuff, and who cares [about that]" she said.

"But it matters because if something is a different species, then we evaluate the risk to that differently than if it's considered just a population of the same species."