The moa diet

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In the summer of 2015, in a remote valley of Fiordland National Park, two scientists discover fossil poo fragments underneath a limestone overhang. Analysis suggests the fragments are from moa and are thousands of years old, so a team returns—three years later—to excavate.

What they find is a rich deposit of moa poo—called coprolites—that accumulated over a period of two millennia, probably between 6800 and 4600 years ago.

But what use is old poo? Scientists can carefully examine the pollen, seeds, DNA and plant microfossils in coprolites to determine what kind of food fuelled the nine moa species that roamed the country.

The team determined that these nuggets of dietary information were from little bush moa (Anomalopteryx didiformis), a mid-sized species between 50 and 90 centimetres tall and weighing 26 to 64 kilograms that inhabited lowland forests. This made it an exciting find. “Until now, only five little bush moa coprolites have previously been identified, all from Central Otago,” says lead researcher Jamie Wood from Manaaki Whenua–Landcare Research.

The poo contained very few seeds, suggesting that little bush moa were not important seed dispersers. But the fossils were rich in ground-fern spores and fronds, suggesting that fern foliage played an important role in this species’ diet, and that the moa spread the plants around.

Because the coprolites were deposited over a period of 2000 years, the researchers were able to trace how the plant matter contained within changed over time. This revealed a shift in the prevailing vegetation from conifers such as miro, mataī and tōtara to the silver beech trees that dominate today.

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