One of our most remarkable exhibits - a three-metre tall female giant moa reconstruction - has turned 100 years old. Built in 1913, she tells a unique (but ultimately tragic) evolutionary tale and recalls museum displays over the century.
Approximately 80 million years ago, the fledgling landmass of Aotearoa New Zealand said its final goodbyes to the ancient continent of Gondwana and drifted out into the Pacific Ocean. This isolated landmass came to be dominated by birds to such an extent that the only land mammal inhabitants present on human arrival were three species of bat/pekapeka.
In the absence of other competitors, such as the mammals found in continental ecosystems, New Zealand's birds adapted to fill all the ecological roles that were vacant in their homeland. Some, like our endemic wrens, were tiny and scuttled around the forest floor like avian mice and others, such as kokako and huia, hopped through the trees like monkeys. Over half of New Zealand's land birds became flightless or had reduced powers of flight.
Flight is an extremely expensive mode of locomotion that requires ongoing inputs of resources to power those big flight muscles. In addition, the only predators threatening New Zealand's birds were native avian hunters such as the New Zealand falcon and Haast's eagle for which the best escape was to hide on the ground rather than take to the skies.
This evolutionary experiment was successful for millions of years but unfortunately the sudden arrival of humans approximately 800 years ago led to rapid decline and extinction of many of these unique and precious bird species. One of the first to vanish was the moa.
A giant of the bird world
Moa were part of a diverse group of large flightless birds called ratites, spread out across the scattered remnants of Gondwana. The group includes the ostrich of Africa, the extinct elephant birds of Madagascar, the rhea and tinamous of South America, the cassowary and emu of Australia, and New Zealand's own national symbol, the kiwi.
We now know there were at least nine species of moa when humans first reached the shores of Aotearoa. Moa ranged from the turkey-sized (30 kg) Mantel's moa (Pachyornis geranoides) up to the two species of giant moa - one from the North Island (Dinornis novaezealandiae) and one from the South Island (Dinornis robustus).
Female giant moa stood approximately two metres high to the top of their back. So in an upright standing position, with their head held high, they could reach three metres tall, allowing them to pluck leaves from tall trees like a giraffe. Their maximum weight was about 250 kg – as much as a cow.
Bones deposits have not only revealed the body size differences in moa species but, as a result of their location have indicated moa had a diverse range of habitat preferences between species. Small species such as the little bush moa (Anomalopteryx didiformis) preferred the dense wet forests. The stout legged moa (Euryapteryx curtus) lived in the forest margins and the upland moa (Megalapteryx didinus) inhabited subalpine tussock grasslands.
The extinction of moa
The people who would have known most about the moa's habits and appearance were the first Polynesian settlers to New Zealand. The exact date of human settlement has been debated for decades, until some ingenious work by New Zealand scientists who carbon dated New Zealand shells and seeds gnawed by the Pacific rat. They found no evidence for presence of rats in Aotearoa prior to 1250 AD, suggesting rats and people colonised around this time.
Archaeological evidence shows that moa were a major part of the settlers' diet. Feathers and skins were used for clothing and bones were made into fishhooks, pendants and other tools. However after millions of years of isolation, moa were likely slow breeders and not able to withstand this harvesting.
Research using carbon dating of moa bones, skin, coprolites (poos) and feathers suggests the youngest moa material available dates to no later than 1450 AD. These new studies provide the sobering reality that the arrival of humans in Aotearoa saw the demise of the mighty moa in little more than 200 years. Given the length of time since this extinction it is thus understandable that there is little oral record of moa by Māori, with stories long ago becoming myth, then legend then lost to the whims of time.
The first moa reconstructions
The first European to attest to the moa's existence, and to attempt to reconstruct moa, was Richard Owen, the British anatomist, biologist and palaeontologist. In 1839, a trader offered him a thighbone fragment, considering it part of a "great New Zealand eagle".
Owen deduced that it was a bone, not from an eagle, but from a giant flightless bird. His colleagues doubted his conclusion based, as it was, on such a small amount of evidence.
However, within a few years he was sent further bone samples, which enabled him to start reconstructing a skeleton. He based his drawings of the moa on the cassowary but it would appear he had not seen a live cassowary, for his illustrations show the bird in an atypical erect posture.
Based on Owen's widely published work, colonial reconstructions (including Auckland Museum's moa) were mostly made in an upright position. It wasn't until the 1980s that a more accurate, typical posture of ratite birds was proposed; where the neck looped down to form an 'S' with the body.
Auckland Museum's moa reconstruction
Moa have been an important part of the Auckland Museum collection since it first opened in 1852. In 1912 a successful public appeal was made to raise £700 to set up a plate-glass case containing a moa restoration. L. T. Griffin built the reconstruction using emu feathers. The ratite display opened with a 'conversazione' attended by about 550 people in October 1913.
The giant moa model has been more or less on continuous display ever since. She has been admired and photographed by local and international tourists for 100 years and is now a historical object in her own right.
Bones to DNA: science reconstructs the moa
While analysis of the bones of moa have provided a huge amount of data on moa biology, recent advances in the study of ancient DNA from moa tissue and bone over the past decade has revolutionised our understanding of the moa. It had been assumed that there were three species of giant moa but the third species was in fact the male of both North and South Island forms. DNA-based sexing revealed surprising and extreme sexual dimorphism (differences between the sexes) in the giant moa. The females could be more than twice as big as the males.
DNA-based studies have also blown away our understanding of moa evolutionary history and challenged our ideas around the arrival of iconic species in New Zealand. For example, for decades it was believed that ratites, including moa, were the perfect example of vicariant speciation: individual ratite species isolated on their respective continental landmasses as Gondwana broke into pieces with genetic relatedness correlating with geographical distance between each population. Under this scenario moa and kiwi should be closest relatives as a result of their long isolation.
However ancient DNA has shown that moa are most closely related to the tinamous of South America, whereas kiwi are most closely related to the elephant birds of Madagascar. Incredibly when you compare the timing of the breakup of Gondwana and the age of these relationships the only way this scenario could have occurred is if both moa and kiwi at some stage flew to an ancient New Zealand landmass and later became flightless.
The moa bone collections of Auckland Museum, and the other major New Zealand museums are a perfect example of how well preserved, catalogued and curated museum collections are essential to advancing scientific research that opens up our understanding of the natural world. Such work can teach us important lessons from the past, and help guide our management of the natural environment into the future.
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Mitchel et al (2014). Ancient DNA reveals elephant birds and kiwi are sister taxa and clarifies ratite bird evolution, Science, 344.
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Listen to a Radio New Zealand interview with former Museum curator Dr Gill where he talks about the 2013 'makeover' of the moa. You can visit her in the Origins Gallery on level two at Auckland War Memorial Museum.
Cite this article
Rayner, Matt and Stevens, Andrea.
Tale of the giant moa. Auckland War Memorial Museum - Tāmaki Paenga Hira. First published: 23 November 2015. Updated: 11 December 2015.