Australasian Science: Australia's authority on science since 1938

Moa Diet Fits the Bill

Australian and New Zealand researchers have discovered that the nine species of moa that roamed New Zealand until the 15th century were able to co-exist because differences in the structure and strength of each species’ bills influenced or dictated their diet.

The moa were herbivores, and were some of the largest birds to have ever existed. The largest species, the South Island Giant moa, weighed up to 240 kg while the smallest, the upland moa, was the size of a sheep. Until now scientists had thought that the huge differences in size between the species determined their foraging behaviour as well as what, when and where they ate.

Prof Paul Scofield of Canterbury Museum says the team took the most complete skulls of each species and scanned them using medical CT scanners. “We then produced highly accurate 3D models of each. This wasn’t a simple job as we didn’t have a single skull that was perfect, so we used sophisticated digital cloning techniques to digitally reconstruct accurate osteological models for each species,” he said.

Using medical MRI scans of mummified remains, the researchers digitally reconstructed the muscles of each species. Software used by civil engineers after the Canterbury earthquakes to identify weak or unsound buildings was then employed to test the strength and structure of each species’ skull.

These were compared with each other and to two living relatives, the emu and cassowary. The models simulated the response of the skull to different biting and feeding behaviours, such as clipping twigs and pulling, twisting or bowing head motions to remove foliage.

Lead author Dr Marie Attard of the University of New England says that the skull mechanics of the moa were surprisingly diverse. “The little bush moa had a relatively short, sharp-edged bill and was superior among moa at cutting twigs and branches, supporting the proposition that they primarily fed on fibrous material from trees and shrubs.

“At the opposite extreme, the coastal moa had a relatively weak skull compared to all other species, which may have forced them to travel further than other moas in search of suitable food, such as soft fruit and leaves.”

“Little has been known about how New Zealand’s ecosystem evolved, largely because we know so little about how moa lived and co-existed.” says A/Prof Stephen Wroe of the University of New England. “This new research advances our understanding about the feeding behaviours of the moa species and their impact on New Zealand’s unique and distinctive flora.”

The findings have been published in Proceedings of the Royal Society B (www.tinyurl.com/hw8wxl7).