Gentoo penguins: three hidden species discovered

Genetics and body measurements reveal that four species of penguin have been masquerading as one...
17 December 2020

Interview with 

Josh Tyler, University of Bath


A gentoo penguin.


The gentoo penguin has been traditionally known as a species of penguin with colonies across the Southern Ocean, first described in the 18th Century by the naturalist Johann Forster. Hundreds of years on, new evidence suggests that his species is, in fact, a multitude. Josh Tyler from the University of Bath explained to Phil Sansom...

Josh - We found that the gentoo penguin, which is currently one species, is in fact four species. And we use DNA evidence, and we use morphological evidence to support our findings.

Phil - Really? Four species were hiding as one?

Josh - Yeah. So this is actually quite a common thing across birds, but also a lot of other species. It's called cryptic species, which are where the organisms are actually separate species but they look identical.

Phil - So how does that bump up your penguin species numbers, then?

Josh - Before this piece of research there were 18, and if we split the gentoo from one to four, that will take the total number up to 21; which is really exciting, that's an over 10% increase in species number.

Phil - Now what exactly are gentoo penguins?

Josh - Sort of medium-sized penguins. You can think of the king and emperor penguin being much larger; the gentoo penguin is the next largest penguin. And they have these really charismatic red tone bills, they have black heads, and they have these two contrasting white patches on their face, above the eyes.

Phil - Do these four species... is it, one lives on one island, one lives on another one, one lives in Antarctica, something like that?

Josh - You're absolutely correct. They have a range that covers the Southern Ocean; they're on a number of different islands there, and also on the actual Antarctic peninsula itself.

Phil - Were you down with the penguins, measuring how tall they are, and getting a bit of their genes, something like that?

Josh - Biology is sometimes not as glamorous as people might think. I was in charge of collating all of the data, but we had teams that went down and collected the genetic data directly from live penguins. And for that we take blood from the penguins, so you would lift the flipper up and take a small amount of blood; or alternatively sometimes you can get DNA from plucked feathers. And for the morphology we use museum specimens, which are much easier to get measurements from; because you imagine holding a penguin squirming, it's quite difficult. So we used museum collections in London and in New York, and you can take your trusty tape measure and your calipers, and you can take all of these really interesting measurements from across the penguin body. And we use those measurements for the physical characters.

Phil - What did you find?

Josh - When we looked at the genetic data, we found that members of each of these different populations were really closely related to each other, to the exclusion of members of other populations on other islands. So you can imagine that the penguins on South Georgia are very closely related to each other, but then they're far more distantly related to the penguins, say, on the Falkland islands. And in terms of morphology, we find there's actually a really interesting statistically significant body size trend. So the penguins in the Falkland islands are fractionally larger than their counterparts, say, in South Georgia, and with the smallest penguins being in the Western Antarctic and on the South Shetland islands,

Phil - How big a genetic difference is that?

Josh - From their genetic signal, we can see that they aren't mixing. And when we did the analysis, there were no individual penguins that might be jumping islands or jumping populations. And that's really exciting, and that is not always the case in genetic analysis, so it really reinforced this idea that they're each their own species.

Phil - Do you know how this dividing into species happened? Is it just the fact that they were separated from each other for a while?

Josh - I think that's absolutely correct. So if you were to imagine the Southern Ocean, the distances between these islands are very large. There's thousands and thousands of kilometres between some of these populations. And also there's a body of water called the polar front, which is where this current that goes around Antarctica sort of envelops Antarctica and the Southern ocean. And actually it's really difficult for penguins to cross that line. And so despite the fact that they can swim a very large distance, these gentoo penguins don't seem to be traveling too far away from their breeding grounds.

Phil - It is definitely interesting, but is it actually important for... I don't know, for the penguins themselves, for their conservation? Because in some ways it seems like it's quite a fine line between a species and just groups living apart, and in some ways it's a line that we humans have created.

Josh - You're absolutely right that there is a very subtle difference maybe between populations and species, depending on what avenue of science you're looking at. The most important thing from this study that comes out is: in terms of conservation, we're trying to protect and conserve diversity of organisms and life on the planet. And when organisations such as the IUCN Red List look at extinction risk, they operate at a species level. And so it's really important, when we find that there are these differences, that they are raised up to the species level so they can be accounted for accordingly. Whilst gentoo penguins across the board, if we took them as one species, are doing fairly well in the fight against climate change, they're not consistently doing well across their range. Some of these island populations are actually seeing marked decreases in population over the past couple of decades. So in order to protect them correctly and introduce measures that will protect the whole diversity of gentoo penguins, it's important to recognise that they're in fact four different species.

Phil - You better introduce me to those four species then!

Josh - Currently they are just named geographically. So we'll have the Falklands gentoo, the Western Antarctic gentoo, the Kerguelen gentoo, and then the South Georgia gentoo. I think that makes it easiest for us.


Add a comment