Scientists use fossilized feces to reconstruct moa diet

(Phys.org) —Until it became extinct in the 15th century, the moa, a flightless bird, played a significant role in New Zealand's ecology. In a study published in the Proceedings of the National Academy of Sciences, Alan Cooper of the University of New South Wales in Sydney and his colleagues reveal they have used coprolites to reconstruct the dietary habits of four moa species. They determined how the moa's extinction has affected New Zealand's ecosystems and considered whether any existing species can take its place.

In the past 50,000 years, many large herbivores, which play an integral part in shaping vegetation communities, have become extinct. By analyzing fossilized feces, or coprolites, scientists can determine what these animals ate and gain a better understanding of the ecological impact of their extinctions. Cooper and his team chose to study the moa because it was the largest herbivore in New Zealand before humans arrived in the 13th century, and moa coprolites are relatively easy to find.

The team examined 51 coprolites found at Daley's Flat in the Dart River Valley in South Island. Radiocarbon dating and analysis of ancient DNA (aDNA) revealed that the coprolites belonged to at least 22 individuals of 4 different species: the South Island giant moa (Dinornis robustus), the upland moa (Megalapteryx didinus), the heavy-footed moa (Pachyornis elephantopus) and the little bush moa (Anomalopteryx didiformis). Before the moa became extinct, nine species lived on New Zealand. This is the first time scientists have been able to study more than one species at a single site.

When the researchers examined fossilized plant materials, pollen and plant aDNA found in the coprolites, they found significant differences in the diets of the four species. They were able to create ecological models explaining how all four could coexist near Daley's flat. While the bush moa found its food in the forests, the heavy-footed moa restricted itself to plants in open herb fields. The South Island giant moa and the upland Moa ate plants from both forests and fields. The South Island giant moa may have eaten low-quality fibrous plant matter that the other, smaller moas would not have been able to digest. The upland moa's diet may have varied seasonally.

The team believe the extinction of the South Island giant moa would have changed the forest canopy and understory, while the extinction of the shorter upland and bush moas would have affected the understory. The extinction of the heavy-footed moa would have caused the loss of herbs that depend on animals for seed dispersal. The researchers found that no living herbivore can fulfill all of these species' ecological roles. The ecological changes stemming from their extinctions are irreversible.