Mid-Holocene coprolites from southern New Zealand provide new insights into the diet and ecology of the extinct little bush moa (Anomalopteryx didiformis)

Abstract

Knowledge about the diets of New Zealand's extinct moa (Aves: Dinornithiformes) is heavily biased towards just three species (Dinornis robustus, Megalapteryx didinus and Pachyornis elephantopus), which represent about 90% of all identified coprolites and gizzard content samples. By comparison, the diets of the other six moa species are poorly known. Here, we report the discovery of a new coprolite deposit attributed to little bush moa (Anomalopteryx didiformis) based on DNA barcoding and former moa species distributions. The deposit is the southernmost site from which moa coprolites have been recovered and just the second to contain mid-Holocene specimens. Moreover, the deposit provides the longest known temporal span (∼2200 years) of moa coprolites within a stratigraphic context. Pollen and plant DNA from the coprolites, as well as associated plant macrofossils, indicate that the deposit spans a period when the forest canopy was transitioning from Podocarpaceae to silver beech (Lophozonia menziesii) dominance about 6800–4600 years ago. Our analysis of coprolite content supports the current hypothesis that little bush moa browsed trees and shrubs within the forest understorey, but provides new evidence that ferns were also an important part of their diet. Based on this finding, we suggest that moa might once have played a previously unrecognised role in the dispersal of ground fern spores throughout New Zealand forests.