Gentoo penguins have long been treated as a single widespread species across the Southern Ocean, but scientists have discovered they are four distinct species. And in the age of avian influenza and climate change, accounting for the differences between those species can influence conservation success.
The new study published in Nature's Communications Biology journal provides detailed genetic, ecological and anatomical evidence of the four distinct species.
"At first glance, all gentoo penguins look the same, but birds from different regions differ in size, bill and body measurements, breeding habitat, ecology and genetics. And that matters, because they are not all doing the same thing, or facing the same threats," said study co-leader Dr Jane Younger , who is a Southern Ocean vertebrate ecologist at the University of Tasmania's Institute for Marine and Antarctic Studies (IMAS).
"For example, during my 2022 field expedition studying gentoo penguins, I observed clear differences between these penguins in the Falklands, South Georgia and Antarctica: different sizes, different breeding environments, and very different ecological contexts.
"These differences are not obvious to a casual observer, but they are real. And if we don't take those differences into account, we risk missing serious declines or disease impacts in particular regions."
Dr Younger first led a study into the genetics of gentoo penguins, to understand how their populations were structured and whether there was interbreeding between regions. But what she and her research team found was much more striking than expected.
"The 'population' was showing distinct genetic differences. So we took a deeper dive, this time into museum collections to measure birds from different regions – and we found consistent physical differences," Dr Younger said.
The study team's first paper proposing that gentoo penguins should be split into multiple species was published in 2020 . But Dr Younger said that proposing new penguin species can be controversial, especially when the birds look superficially similar.
"Now our new study provides the in-depth evidence to support our claim," she said.
"It combines whole-genome data, morphology, ecological niche modelling and evolutionary analyses, and supports recognising four gentoo penguin species across the Southern Ocean."
Dr Younger said that recognising these distinct species correctly will enable conservation assessments to reflect the actual threats different species are facing in different regions.
"At the moment, because gentoo penguins are treated as one species and they are doing so well on the Antarctic Peninsula, it drives an overall positive trend. But that masks major regional differences.
"While they are thriving on the Antarctic Peninsula, expanding south and increasing in population size, in the Falklands they have been decimated by avian influenza over the past few years – and on Macquarie Island, they are declining."
"Meanwhile in some other regions, we don't have reliable recent monitoring data, so we don't really know how they are doing."
The new study proposes a formal taxonomic revision recognising four gentoo penguin species, including one newly described species from Kerguelen. It also calls for taxonomic authorities and conservation bodies to consider these findings and to assess the conservation status of each species separately.
"The discovery of these four gentoo penguin species highlights how little we still understand about the amazing diversity of life on this planet," Dr Younger said.
"It really shows why taxonomy is not just academic, it shapes whether we can recognise species at risk before it is too late."
Banner image by Milan Sojitra IMAS
