Page last updated at 01:55 GMT, Wednesday, 19 November 2008

Rare penguin took over from rival

The wing bones of the two penguin species differ in size
The yellow eyed penguin is bigger than its extinct relative

The arrival of humans in New Zealand may have led to the extinction of one penguin species - to the advantage of another.

Writing in the Royal Society journal Proceedings B, researchers say the extinct species lived in areas now home to New Zealand's rare yellow eyed penguin.

The extinction is thought to have occurred as recently as 500 years ago.

Early settlers wiped out many of New Zealand's unique animal species.

Scientists from the University of Otago, New Zealand, say they discovered the new species unintentionally when researching the genetic history of the yellow eyed penguin.

Although there are only around 7,000 yellow eyed penguins they have a wide range, being found on the sub Antarctic Campbell and Auckland islands as well as 700 km (435 miles) further north on the South-East coast of New Zealand's South Island.

DNA evidence

The discovery of the new species was something of a mystery according to Sanne Boessenkool, who led the research.

"They were around 10% smaller [than the yellow eyed penguin] they were very closely related, but we can't say if they had a yellow crown. There are no records of their existence from the local Maori people," she told BBC News.

European collectors took penguins to museums around the world
DNA samples were taken from the feet of stuffed penguins

DNA analysis compared modern penguins with samples from the feet of 100-year-old museum specimens and 500-year-old bones from both the sub-Antarctic islands and early Polynesian settlements on New Zealand's South Island.

The older bones found in South Island were smaller than those from the modern yellow eyed penguins and contained different DNA.

The DNA from the sub-Antarctic islands matched that of the modern birds.

This geographic variation and subtle differences in the structure and shape of the bones led the researchers to conclude that New Zealand's South Island had been home to a different, now extinct penguin and to designate this as a new species.

You get a complete shift in just a couple of hundred years
Sanne Boessenkool, University of Otago

Hunting Penguins

Sanne Boessenkool says it's hard to pinpoint exactly why the penguins became extinct but its likely they were eaten by Polynesian settlers who arrived from about 1280AD.

"The fact we find these bones in archaeological sites, villages or settlements, suggests hunting played a role. The birds were an easy target, easy to take and there were never very many of them,"

The new species has been named Megadyptes Waitaha. The Waitaha were the first Polynesian tribe to occupy South Island.

M. waitaha's rapid replacement by its close relative the yellow eyed penguin, Megadyptes antipodies, raises questions about current dating techniques and extinction theories, says Sanne Boessenkool.

"Often when we look back in time and date bones we don't think a couple of hundred years is important, but here you get a complete shift in just a couple of hundred years. These patterns might be more common, a view we don't consider when looking at large scale extinction events,"she explained.

The penguins moved further north
Yellow eyed penguins increased their territorial range

Shy and secretive

By the time Europeans arrived in South Island in the 1800s, the yellow eyed penguins had already taken over the sites left by its relative. The bird's breeding behaviour makes it an unlikely coloniser. Sanne BoessenKool has studied them in the field for many years.

"They are very secretive, shy and difficult to monitor, they don't live in big colonies, but build their own nest perhaps under some bushes," she commented.

Despite their fragile foothold the researchers say these incoming penguins probably survived on New Zealand's South Island due to a change in human behaviour.

Either the human settlers moved further north due to a lack of food following the extinction of the earlier penguins and other species, or they had begun to develop some of the conservation principles found in contemporary Maori culture and so saw a need to allow these penguins to survive.

Sanne Boessenkool is now investigating how and when the penguins moved across from the sub-Antarctic Auckland and Campbell islands.

"It is a mystery, were now looking at the ways it may have colonised, if its a small group or if they are still coming," she said.

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