Consider the moa, the flightless, Muppet-esque bird that once dominated the New Zealand landscape. The nine known moa species ranged greatly in size, from 12-foot-tall, 440-pound beasts to two-foot-tall, 60-pound darters. But they all met a similar fate, hunted to extinction in the 15th century by Polynesian settlers. Scientists knew a fair amount about the moas, including, thanks to some fossilized poop, what they ate. But they didn’t know how they ate. It may not seem so important, but when the moas vanished, they left a hole in the ecosystem; because there were no grazing mammals in New Zealand at the time, these large herbivores had played an outsized role in shaping the landscape, from thinning out vegetation to dispersing seeds. So to find out more about how the moas fed, a squad of scientists from Australia and New Zealand decided to use the magic of 3-D software (and an assist from a mummy) to digitally reconstruct the heads of several moa species, and then feed them a snack. Here’s how they did it.
Step 1: Build a Digital Skull
Using a computed tomography (CT) machine like you’d find in a hospital, the scientists generated scans of skulls taken from five different moa skeletons: an Upland Moa, a South Island Giant Moa, a Little Bush Moa, a Crested Moa, and a Coastal Moa. For comparison’s sake, they also scanned the skulls of an Emu and a Southern Cassowary, modern-day relatives of the moas (all are members of the ratite family). Then, using a technique called finite-element modeling, the scientists translated those medical image files into interactive digital 3-D models of each skull. Not all of the moa skulls were intact, so the team copied and pasted existing symmetrical pieces to fill in the holes, paying extra attention to the jawbones.
Step 2: Borrow Mummy Muscles
The team needed more than skulls—they needed jaw muscles, too. So they asked the Museum of New Zealand if they could borrow its resident moa mummy, an Upland Moa bust—discovered by gold miners in the 1860s—whose soft tissue was nicely preserved. The team carted the bust to a hospital for an MRI scan, which they then ran through their 3-D software. Then they inserted the digitized muscle tissue into the digitized skulls. To figure out each species’ muscle strength, they calculated the mummy’s jaw power, and then scaled that figure according to each species’ mass, which was determined by measuring the skeletons’ femurs. (In moas, femur circumference corresponds predictably with body mass.)
Step 3: Feed the Moa
With the moas built, it was time to play with them. Using simulation software created to test the structural integrity of buildings in strong winds, the researchers ran each of their digitized skulls through four distinct feeding motions, such as clipping a branch with one side of the jaw or biting down on a branch and shaking it from side to side. During each simulation, the software measured how much stress was put on the bird’s mandibles. By assuming that each species preferred the feeding motion that caused it the least biomechanical stress, the scientists were able to analyze the resulting stress diagrams and match each feeding behavior to the species that likely employed it.
So how did the moas eat? Surprisingly, each moa species “appears to be using different feeding strategies, with some being more specialized than others,” says Marie Attard, a researcher at Sheffield College in England and leader of the study, the results of which were published earlier this year in the journal Proceedings of the Royal Society B. These different feeding styles, which may have evolved to reduce interspecies competition, would have, in turn, affected what the moas ate, where they lived, and what ecological role they played. Another takeaway? The moas had fed differently than the Emu and the cassowary. “There have been several politicians over the years that have advocated introducing large modern ratites into New Zealand to fulfill the ecological role of the moa,” says Attard. But her research suggests that when it comes to moas, there’s no substitute for the real deal—short of a Jurassic Park-style resurrection (see sidebar), the landscape the moa knew and shaped is gone for good.