Study shows that the Moa was killed off by settlers

The last known moa lived in the mountains of north-west Nelson. Photo / Supplied

Even small human populations can wipe out big animal species, according to local researchers who suggest moa extinction was rapid.

Researchers from the University of Canterbury and University of Otago contributed to the new findings, which appeared in the journal Nature Communications.

Professor Richard Holdaway from Canterbury and Otago's Chris Jacomb said early Polynesians who caused moa extinction in little more than a century had amongst the lowest human population densities on record.

They found that during the peak period of moa hunting, there were fewer than 1500 Polynesian settlers in New Zealand, or about 1 person per 100 square km. New Zealand's population density today is 17 per square km.

The researchers started with the latest estimate for a founding population of about 400 people, including 170-230 women. They then applied population growth rates in the range achieved by past and present populations and modelled the human population size through the moa hunter period and beyond.

Prof Holdaway and Mr Jacomb said when moa and seals were still available, the better diet likely fuelled higher population growth.

But the moa's total extinction most probably occurred within a decade either side of 1425. This was barely a century after East Polynesians settled the earliest well-dated site, at Wairau Bar near Blenheim.

The last known moa lived in the mountains of north-west Nelson. The researchers said it was often suggested that people could not have caused the extinction of megafauna such as the mammoths and giant sloths of North America and the giant marsupials of Australia, because the human populations when the extinctions happened were too small.

Prof Holdaway and Mr Jacomb said the extinction of the New Zealand terrestrial megafauna of moa, giant eagle, and giant geese showed that population size can no longer be used as an argument against human involvement in extinctions elsewhere.