Importing Australian emus and cassowaries to New Zealand to fill the ecological gap left by the extinction of the moa would not work, according to insights into the giant flightless birds’ feeding behaviours.
The findings, reported in the journal Proceedings of Royal Society B, show the nine species of moa were able to co-exist in New Zealand by using different feeding strategies.
With the coastal and other moa now extinct, there’s nothing in New Zealand to fulfil the range of ecological rolls the moa had.
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Dr Marie Attard
“My research shows each moa species specialised in different types of food and it’s not certain we can introduce other species to New Zealand to fill those roles because they’re quite diverse,” the study’s lead author Marie Attard, of the University of New England, said.
“I don’t think you can introduce a single species like an emu or cassowary into New Zealand to act as an ecological surrogate — which is what others have proposed in the past — to fill the role of the moa.”
It is thought that the extinction of these birds 550 years ago left indelible holes in New Zealand’s ecosystem and likely led to drastic changes in fire frequency, regeneration patterns and seed dispersal opportunities of plants.
But scientists have had little real understanding of how this damage manifested because they know little of how the moa lived and co-existed.
Dr Attard and her colleagues obtained CT scans of the skulls of five different moa species and conducted MRI scans of the mummified remains of one moa that still had all its jaw muscles attached to create the first three-dimensional computer models of how the muscles worked in each bird.
The team then compared the moa models to 3D models created from the skulls of its Australian cousins the cassowary (Casuarius casuarius) and emu (Dromaius novaehollandiae).
The models showed different species used different skull biomechanics depending upon the types of food they ate.
“We could simulate how the birds would bite down on a twig which is how they could grab vegetation off plants,” Dr Attard said.
“We also did other simulations like shaking, bowing and twisting the head, as well as various other strategies that we find in living birds to see which of those methods were best suited for different types of feeding habits.”
The researchers were surprised to discover how diverse the different moa species’ feeding behaviour was.
The little bush moa (Anomalopteryx didifornis) possessed a relatively short, sharp-edged bill designed to cut twigs and branches, supporting the idea that they primarily fed on fibrous material from trees and shrubs.
“Another species called the coastal moa (Euryapteryx curtus), seemed to be very suited to eating soft fruits, and would have ranged over a large area to find those fruits, which made them quite good at distributing seeds,” Dr Attard said.
“With the coastal and other moa now extinct, there’s nothing in New Zealand to fulfil the range of ecological roles the moa had.”
The team found the bite mechanics of both species of Australian birds were quite weak compared to the moa, which suggested the extinct birds used different feeding strategies their modern cousins.
Dr Attard said the findings indicated the Australian birds would be poor replacements for moa and would not be able to restore lost ecosystems.
“Kiwis will be really glad that no other species will be introduced into New Zealand — no foreign species should have been introduced in the first place,” Dr Attard said