Millions more moa in Aotearoa

By SIMON COLLINS

The flightless moa that were once our biggest land animals may have been dying of natural causes well before Maori hunters arrived to finish them off.

Biologist Neil Gemmell of Canterbury University has calculated there were between 3 million and 12 million moa at their population peak 1000 to 6000 years ago - far more than the estimated 158,000 at the time Maori arrived about 700 years ago.

Dr Gemmell said the moa might have been devastated by a volcanic eruption, such as successive eruptions of Lake Taupo which dropped ash over much of the North Island, or through diseases spread by new bird species arriving from Australia.

But his estimate, published last Wednesday in the Proceedings of the Royal Society of London, has been dismissed as ridiculous by Te Papa palaeontologist Trevor Worthy, co-author of the 2002 book Lost World of the Moa.

Dr Gemmell agreed that his figures were highly uncertain.

"Perhaps you do have to come out with something outrageous in order for us to settle on something that is more reasonable," he said.

"I certainly think their previous number may be wrong. Our number could be half what we say it is, but I don't think it's going to be much more than that."

The previous estimate of 158,000, published by two Canterbury researchers, Richard Holdaway and Chris Jacomb, in the equally eminent journal Science in 2000, was based on analysing moa remains in each region of the country.

That figure, in turn, was roughly twice a previous estimate by Professor Atholl Anderson in 1989.

Dr Gemmell, aged 38, used a new method, developed to calculate past whale populations, which derives historical numbers from the genetic diversity in an existing population or in the bones collected from an extinct species.

He and two co-authors used 57 samples of DNA from bones of the biggest moa species, dinornis, to calculate that there must have been between 299,000 and 1.4 million dinornis at the population peak.

They then multiplied those numbers by about 10 because dinornis represented only 7 to 14 per cent of the fossil records of all moa species, depending on the site.

However, Mr Worthy said Dr Gemmell's calculations were based on the false assumption that moa interbred throughout both the North and South Islands.