Ancient moa remains lasted 6800 years
In January 2015, Dr Jamie Wood and grad student Theresa Cole discovered moa turds in a rock shelter in a remote valley about 20 kilometres south of Manapo¯ uri in Fiordland.
They were on the North Branch Borland River walking track and came across a rock shelter that opened roughly to the northeast.
This was exactly the sort of place that moa remains survive on the South Island – protected from the prevailing wet weather coming in from the southwest and kept dry by the overhang of rock.
Sure enough, the pair observed five fragmentary moa coprolites – as ancient dung is known to scientists – beneath a wooden platform used by trampers in the rock shelter.
They knew what to look for. Wood has a PhD in palaeoecology from the University of Otago and is now a researcher at Landcare Research, and Cole now has her PhD and is at the University of Copenhagen in Denmark.
For more than 20 million years, moa were the tallest and heaviest herbivores on the continent of Zealandia.
But they were hunted to extinction sometime in the 1400s, and paleobiologists must now travel to the remotest places to find traces of their existence.
As these specimens were at risk of being damaged or destroyed if left in place, they were collected and taken to a lab for preliminary inquiry.
Radiocarbon analysis showed they were several thousand years old, and permits were sought to properly excavate the Borland rock shelter.
Wood, Cole and archaeologist Shar Briden got back to the overhang in March 2018 and removed three boards from the platform.
Then they created a 40 centimetre square hole mostly with brushes.
In the top layers, they found lots of ungulate fecal pellets and plastic. Deeper down, they found more moa coprolites and plant remains probably the same age as the dung.
The results of their dig are now in. The coprolites were left by little bush moa (Anomalopteryx didiformis), the smallest moa species. They were 50 to 90cm tall and weighed between 26 and 64 kilograms. These coprolites were 4647 to 6849 years old and indicate the moa used the rock shelter for a span of 2200 years.
This was the southernmost site from which moa coprolites have been found so far. Analysis showed at least four individual birds left the specimens.
Analysis of pollen, spores, plant DNA and leaf remains in the coprolites ‘‘provide further evidence that little bush moa inhabited forests where they browsed a variety of trees and shrubs’’, wrote Wood and colleagues in a paper in the peerreviewed journal, Quaternary Science Reviews.
They established the ‘‘most convincing evidence yet’’ that fern and mistletoes were also important components of little bush moa diet and that the birds probably dispersed ground fern spores throughout the forests.
These birds lived during a time when the forests of Fiordland were undergoing significant change.
‘‘The forest canopy was transitioning from conifers (dominated by miro, ma¯ tai , to¯ tara and mountain toatoa from the Podocarpaceae family) to silver beech (Lophozonia menziesii) dominance about 6800 to 4600 years ago,’’ they wrote.
The coprolites (and moa) survived those changes, and the researchers were convinced that the wooden platform helped to protect the prehistoric deposits under it, even if only for a few decades.