Paleobiologist Richard Holdaway of Palaecol Research in Christchurch, New Zealand, reporting in today's journal Science, used a computer simulation to figure out how the moa population would respond to hunting pressure from a 100-person band of settlers. By using information known about other large birds living in forests, he estimated that about 160,000 moas were alive when Polynesians reached New Zealand in the late 13th century.
Scientists know about moas only from fossils and archaeological digs.
Even using the most conservative estimates of moa consumption and human population growth, he found that all the big birds vanished about 160 years after people arrived. Moas, thought to live 30 or 40 years and to reproduce slowly, just couldn't handle the additional predation from humans, Holdaway says. To verify when moas became unavailable for food, co-author Chris Jacomb, an archaeologist at Christchurch's Canterbury Museum, dated bits of sea shells from excavated garbage pits and found that people switched from munching moa to grubbing for clams around the late 14th century. That's a better way to figure out when moas went extinct than dating moa bones and hoping they were bones from the last moa ever, Holdaway says. I don't believe people would eat shellfish if they could have turkey.