Flightless Giant's Flower Diet Revealed by Poop Fossils

If Big Bird had ever invited his weird armless cousin from Down Under to visit Sesame Street, American kids would have met the moa. These flightless birds lived in New Zealand until hungry humans arrived; the last moa species predictably went extinct around 1500. Thanks to fossilized droppings, though, scientists are learning how the hapless giants lived, what they ate, and what holes they left in the ecosystem by vanishing.

Here are some fossil turds. In polite company, you can refer to them as "coprolites."

Researchers led by Jamie Wood of Landcare Research in Canterbury, New Zealand, discovered about a hundred moa coprolites in the entrance to a remote cave. Thanks to the sunlight and breezy air, the desiccated droppings had been well preserved. They picked out 35 choice specimens (above) to take back to the lab.

To turn the rocky clumps into open books, the researchers used every tool they had. They carbon dated the coprolites to find out their ages. They cracked them open and looked for tiny bits of leaves or seeds that had been fossilized inside. They extracted DNA from the coprolites, both belonging to the moas that had left them behind and the plants those birds had eaten. And they dissolved their samples to get out pollen grains, which could be traced to plant species.

There were 11 or so species of moa alive in the past, ranging from hefty to alarmingly large. The biggest were nearly twice the weight of a large ostrich today. However, the DNA sequences inside the coprolites revealed that they all belonged to just one species: the upland moa, Megalapteryx didinus. Jamie Wood says this was one of the smaller moa species, standing about three feet tall (minus the neck and head) and weighing around 80 pounds. "It had sharp claws and was feathered right down to the feet," he adds.

The upland moa was also the last one to go extinct. Carbon dating showed that the most recent fossil droppings were only dropped about 700 years ago. Other coprolites in the cave were closer to 6400 years old. Based on the pollen and moa DNA inside them, the authors think certain clusters of coprolites within their sample came from "a single defecation event." Nearly half their sample might be accounted for by just five birds, using this cave as a latrine at different points in history.

Plant DNA, pollen, and microscopic fossils inside the coprolites revealed what those historic birds had recently eaten. The upland moa wasn't picky: At least 67 types of plants were accounted for in the droppings. Some of the pollen may have blown onto the birds' food from elsewhere. But overall, the upland moa was an indiscriminate herbivore, eating whatever plants were around. In addition to trees, shrubs, and grasses, it likely ate the flowers of flax and fuchsia plants. (These nectar-filled treats are eaten by some living birds as well.)

The pollen and seeds inside the coprolites came from plants that flower in the spring and summer, which let the researchers infer that the birds moved to warmer forests during the winter months. And they squeezed a further bit of information from the stony droppings: Seeds from several plant species had survived intact inside them. This means the birds would have scattered these seeds—possibly to sprout again—wherever they did their business.

Certain regional plant species may have relied on the moas to distribute their seeds in this way. In evolutionary terms, the birds haven't been gone long; the authors point out that some very old trees alive today might have been planted by moas. Dominos tipped by the extinction of the moa may still be falling throughout the New Zealand ecosystem.

Jamie Wood says he and his colleagues still haven't exhausted the information that can be extracted from a fossil turd. In the future, they'd like to use DNA evidence to discover the sex of each dung-depositing moa. "Some moa species had vast size differences between sexes, so we are interested in working out whether the diets and habitat use also varied with the different sexes," he says.

Six-thousand-year-old poop might not have gone over well as a Sesame Street topic, even if Big Bird's extinct cousin had shown up. But for scientists, the fossils are providing an elementary education about a vanished species.

Jamie R. Wood, Janet M. Wilmshurst, Steven J. Wagstaff, Trevor H. Worthy, Nicolas J. Rawlence, & Alan Cooper (2012). High-Resolution Coproecology: Using Coprolites to Reconstruct the Habits and Habitats of New Zealand’s Extinct Upland Moa (Megalapteryx didinus) PLoS ONE : 10.1371/journal.pone.0040025


Images: Upland moa by George Edward Lodge/Wikipedia; coprolites Wood et al.