Poo study shows deer and moa had wildly different effects on NZ forests

Two moa shown in an illustration by John Megahan.

A long-running debate that deer might fill the extinct moa's place in the ecosystem has been snuffed out in a new study comparing prehistoric moa poo with deer droppings.

Using plant pollen from these faeces, Kiwi researchers reconstructed the diet of moa and deer and found the moa's was richer and more varied, owing to the diversity in New Zealand's prehistoric forests.

Deer have likely driven out many species that moa used to feed on, suggesting the two animals had very different impacts on their environment, the authors say.

Reacting to the research, Dr Nic Rawlence, Director, Otago Palaeogenetics Laboratory, University of Otago, said previous research had shown moa were truly unique. No suite of feathery or furry pretenders could replace the broad range of feeding types exhibited by moa.

Their extinction was a sucker punch to the way ecosystems worked in Aotearoa New Zealand.

However, until now it had been difficult to test for differences in the diet of moa and deer from the same locality but at different times.

Deer droppings. Photo / File

This was to ensure that dietary reconstructions reflected local habitat and dietary preferences.

Now Jamie Wood and Janet Wilmshurst from Manaaki Whenua Landcare Research have done just this.

They collected prehistoric moa coprolites (desiccated faeces) and deer droppings from within native forest at Daley's Flat, (up the Dart River Valley), that had experienced little human impact.

Using plant pollen from these coprolites and droppings, the pair reconstructed the diet of moa and deer.

They found that the diet of moa and deer differed markedly, with a much richer and varied diet in moa, indicating a richer and varied forest understory in prehistoric New Zealand compared to today.

Rawlence said this highlighted that the higher population densities and browsing pressure of deer, compared to moa, had driven the loss of many understory species that could survive being eaten by moa, but not deer.

"Ever wondered why our native forests are relatively open under the canopy. Now you know why.

Photo / File

"This ingenious study highlights that moa and deer have different impacts on our native forests. It is the final nail in the coffin for any idea that deer fill the same job vacancy in the ecosystem as moa.

"Deer are a pest damaging our precious remaining ecosystems and should be treated as a pest. End of story.​"

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