New Study Provides Insights into Diet of Extinct Little Bush Moa
Paleontologists have examined 6,800- to 4,600-year-old coprolites attributed to the little bush moa (Anomalopteryx didiformis). The results support the current hypothesis that this moa species browsed trees and shrubs within the forest understorey, and provide new evidence that ferns were also an important part of its diet.
Most of what scientists currently know about the diets of New Zealand’s extinct moa 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.
Moa coprolites and gizzard contents can be dissected and analyzed under the microscope or using DNA identification techniques to decipher what the birds ate. The contents can also be screened to see what seeds the birds may have dispersed.
A rare deposit of 6,800- to 4,600-year-old moa coprolites was recently discovered in Fiordland National Park in the southwest corner of the South Island of New Zealand.
“This rock shelter deposit is scientifically very important as it is the southernmost site from which moa coprolites have been recovered, with the longest documented timespan of coprolite accumulation (2,200 years) preserved within a sediment horizon in a single place,” said Dr. Jamie Wood, a researcher with Manaaki Whenua — Landcare Research.
“Until now, only five little bush moa coprolites have previously been identified, all from central Otago.”
Using DNA analysis and known moa species distributions, the scientists attributed the deposit to the little bush moa, a small-to medium-sized species of moa that lived in lowland closed-canopy forests throughout New Zealand.
Pollen and plant DNA from the coprolites, as well as associated plant macrofossils, show that the deposit spans a period when the forest canopy was transitioning from conifers (dominated by miro, matai, totara and mountain toatoa from the Podocarpaceae family) to silver beech (Lophozonia menziesii) dominance about 6,800 to 4,600 years ago.
DNA, pollen and leaf cuticle fragments of the red mistletoe (Peraxilla tetrapetala), a species usually associated with silver beech, were also found in the little bush moa coprolites.
The nutritious leaves of this mistletoe are highly palatable and today are also sought out by the introduced possum (Trichosurus vulpecula) and browsing mammals such as deer.
The little bush moa coprolites contained very few seeds compared with other analysed moa coprolites.
“This observation was interesting because it contrasts with what we know about other moa species which played an important role dispersing tiny seeds (less than 3 mm) of many plant species in their droppings,” said Dr. Janet Wilmshurst, a researcher from Manaaki Whenua — Landcare Research and the University of Auckland.
“The near absence of seeds in the little bush moa coprolites indicates they were not important seed dispersers, and that they may have been targeting the largest conifer seeds which get totally ground up in their muscular gizzards and destroyed rather than dispersed.”
The study also provided striking new evidence that the foliage of ground ferns were an important part of their diet.
“While little bush moa may not have been great seed dispersers, based on our finding of ground fern DNA, frond cuticle remains and high spore counts, they may have played a previously unrecognised role as dispersers of ground fern spores throughout New Zealand forests,” Dr. Wood said.
The study was published in the journal Quaternary Science Reviews.
Jamie R. Wood et al. 2021. Mid-Holocene coprolites from southern New Zealand provide new insights into the diet and ecology of the extinct little bush moa (Anomalopteryx didiformis). Quaternary Science Reviews 263: 106992; doi: 10.1016/j.quascirev.2021.106992