Gentoo penguins should be reclassified as four separate species, scientists have said.

Researchers from the Milner Centre for Evolution at the University of Bath analysed the genetic and physical difference between penguin populations around the southern hemisphere.

They say that counting the birds into four separate species will help their conservation, as it will be easier to monitor any decline in numbers.

Gentoo penguins, which have the Latin name Pygoscelis papua, live in a range of latitudes in the southern hemisphere and are currently split into two subspecies, P. p. ellsworthi and P. p. papua.

The researchers say these two subspecies should be raised to species level, and two new species created named P. poncetii and P. taeniata.

Their work is published in the journal Ecology and Evolution.

Dr Jane Younger, from the Milner Centre for Evolution at the University of Bath, said: “For the first time, we’ve shown that these penguins are not only genetically distinct, but that they are also physically different too.

“Gentoos tend to stick close to their home colonies, and over hundreds of thousands of years have become geographically isolated from each other to the point where they don’t interbreed with each other, even though they could easily swim the distance that separates them.

“The four species we propose live in quite different latitudes – for example P. ellsworthi lives on the Antarctic continent whereas P. poncetii, P. taeniata and P. papua live further north where conditions are milder, and so it’s not that surprising that they have evolved to adapt to their different habitats.”

The study examined the genomes of penguin populations living in the Falkland Islands and South Georgia in the southern Atlantic Ocean, the South Shetland Islands in the Antarctic and Kerguelen Islands in the Indian Ocean.

Researchers used the data to create an evolutionary tree to understand the relationship between the different populations.

This data, along with measurements of museum specimens from each of the populations, showed clear physical and genetic differences between the four groups.

Josh Tyler, a PhD student, said: “They look very similar to the untrained eye, but when we measured their skeletons we found statistical differences in the lengths of their bones and the sizes and shape of their beaks.

“It’s a similar story to giraffes, which were revealed in 2016 to be four genetically distinct species.”

The scientists say that defining the populations as four separate species gives conservationists a better chance of protecting their diversity.

This is because if there is a decline in one of the groups, it will change the threat status as defined by the IUCN Red List.

“Currently Gentoo penguins are fairly stable in numbers, however there is some evidence of the northern populations moving further south as the climate gets warmer, so we need to watch them closely,” Dr Younger added.

An international committee of scientists will review the proposed changes and assess all the evidence in the scientific literature before accepting the reclassification.

The study also involved scientists from Loyola University Chicago, Cornell University and the University of Minnesota.