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© University of AucklandMOA: Artist's impression of an Upland Moa, Megalapteryx didinus.
The flightless moa was doomed the moment humans landed in New Zealand, new research suggests.

Whether they were big or small, moa were wiped out in 200 years and the last were killed nearly 600 years ago, between 1440 and 1445.

When humans arrived there were an estimated 58,000 moa in the country.

"Moa were hunted to the point of being critically endangered within 150 years of settlement, after which only a few small populations clung on in remote mountain regions, but only for another 50 years before they vanished forever," George Perry of the University of Auckland's School of Environment and School of Biological Sciences says.

The findings, with input from Landcare Research, used a large database of radiocarbon dates and has been published in the journal Quaternary Science Reviews.

"This is the first time we have been able to show that extinction was both rapid and synchronous across New Zealand," Perry said.

Landcare palaeoecologist Janet Wilmshurst said they had produced a "time zero" for the beginning of the decline for the moa which was the arrival of humans in the mid-13th century.

"Previous studies have relied on older and less precise dates, so what this research does is help settle a long-standing debate about the speed and nature of this extinction," Wilmshurst said.

"We now have a much clearer understanding of when and how it happened."

Size made no difference - from more than 200 kilograms to less than 50kg moa were all killed.

The research analysed 653 radiocarbon dates from moa remains to pinpoint the extinction time line.

Landcare's Jamie Wood said the research provided insights into how intense hunting pressure on the slow-breeding birds produced a catastrophic decline.

"We always suspected extinction was remarkably rapid for the moa and we now have evidence that none of them survived into the post-European era," he said.

Perry said that with about 58,000 moa in the country and a human founding population in New Zealand of 100 people growing at 1 per cent a year, it would have taken just five birds harvested per person per year to eliminate moa within 200 years.

The paper's authors said extinction occurred contemporaneously at sites separated by hundreds of kilometres.

"Our results demonstrate how rapidly megafauna were exterminated from even large, topographically and ecologically diverse islands such as New Zealand, and highlight the fragility of such ecosystems in the face of human impacts," the paper said.

The authors said that while there was little doubt human activity killed the moa, the way it reached extinction was unclear.

"Extinction seems to have loosely followed the 'overkill' model, but whether it occurred contemporaneously throughout New Zealand or followed a 'blitzkrieg' rolling extinction front is again less clear."

Assuming hunting was the key factor, the researchers said their extinction models provided insights into the movements and strategies of Polynesian hunters in New Zealand.