For millions of years, nine species of large, flightless birds known as Moas thrived on the islands today known as New Zealand (Aotearoa). The evolutionary lineage of these Moas dates back sixty million years. The Moa fed on twigs and plants. The Moas had one main predator and that was the Haast’s Eagle. The wingspan of Haast’s Eagle was up to three meters, body length was up to one and a half meters, and adults stood ninety centimeters tall.
These islands had been isolated for eighty million years. The Moas had few predators prior to human arrival. It is thought that the Moa arrived in Aotearoa sixty million years ago.
It is likely that the Haast’s Eagle and the Moa evolved due to island gigantism, a phenomenon in which animals isolated from more diverse populations of other animals end up much larger than they would be on the mainland. There were no land animals there at the time. Birds and reptiles evolved to fill up these empty ecological niches that would have been typically filled up by larger mammals. Evolutionarily speaking, the Haast’s Eagle took the place of the apex predator that hunted grazers, a space taken up by the Moa species.
The two largest species of Moas reached about 3.6 meters in height with neck outstretched, and weighed about 250 kg. The smallest of the Moas, the Bush Moa, was 1.3 metres tall and weighed 30 kg.
When the Maori first arrived they called the islands Aotearoa, meaning ‘Land of the Long White Cloud’. It is estimated that, when Maori settled Aotearoa circa 1280, the Moa population was about 58,000.
The Māori were the first inhabitants of Aotearoa. It is believed the Māori came from islands in Polynesia in the South Pacific Ocean. The Māori arrived in Aotearoa in several waves of canoe voyages. It is estimated that the ancestors of the Moa existing in Aotearoa when the Maori arrived had been living there for nearly six million years.
About 600 years ago the Moas became extinct. Their die-off coincided with the arrival of the first modern humans on the islands, the Maori. A new genetic study of Moa fossils points to humankind as the sole perpetrator of the birds’ extinction. Moa extinction occurred between 1280 and 1460, primarily due to overhunting by the Māori. The native species were not equipped to cope with human predators. Recent research strongly suggests that the events leading to extinction took less than 100 years.
When the Maori hunted the Moa to extinction in the first half of the 1400s, barely a century after their arrival, there was no prey large enough left to sustain the Haast’s Eagles that hunted the Moas for food, so the Haast Eagles also became extinct soon afterwards.
The Moas present us a particularly important insight because they were the last of the giant species to vanish, and they did so recently, when a changing climate was not a factor.
Archaeologists know that the Polynesians who first settled Aotearoa ate Moas of all ages, as well as the birds’ eggs. Archeologist Morten Allentoft said. “If you hunt animals at all their life stages, they will never have a chance.” The Moa egg could be as large as eighteen by twenty four centimeters.
Analysis of mitochondrial and nuclear DNA from Moa bones led archeologists to determine that the Moas’ genetic and population history over the last four thousand years. Extinction events can be seen in a species’ genetic history. As the animals’ numbers dwindle, they lose their genetic diversity. But the researcher’s analysis failed to find any sign that the Moas’ populations were on the verge of collapse. The report published in the Proceedings of the National Academy of Sciences in 2014 stated that the birds’ numbers were stable during the four thousand year period prior to their extinction and in fact even appear to have been slowly increasing when the Polynesians arrived.
“The inescapable conclusion is these birds were not in the old age of their lineage and about to exit from the world. Rather they were robust, healthy populations when humans encountered and terminated them.” says Trevor Worthy, an evolutionary biologist and Moa expert at Flinders University in Adelaide, Australia.
The scientific models used to gauge the population size of the Maori people in Aotearoa during the Moa extinction period reveal a human population size of under two thousand individuals. The models also reveal that it was unlikely that the human population was greater than one thousand five hundred individuals during the peak period of Moa over-kill and habitat destruction. Notwithstanding making allowances for Moas being long-lived birds with protracted growth and low reproductive rates and their being naive to human predation, their extinction was caused by a remarkably low number of people. This seems to indicate that the extermination was executed with particular tenacity and savagery.
By the early 1400s the Moa populations had plummeted. We have learnt, from orally transmitted Maori tradition, that at the time of the Moa extinction, tracking down and killing the last surviving Moa individuals by a Maori tribesman, was considered to be an act of bravery. And so it went. The Maori bravely wiped out every last Moa of all the nine species.