A little over 700 years ago, humans finally discovered the last habitable place on Earth, Aotearoa-New Zealand (Wilmshurst et al., 2011; Mulrooney et a;, 2011; Bunbury et al., 2022). They found a land where large flightless birds (including the now-extinct moa) abounded, and even the driest parts were covered in forest. Neither lasted long. The dry forests succumbed to fire (Perry et al., 2012), and the moa to a mixture of habitat loss and unsustainable hunting levels (Worthy and Holdaway, 2002), and introduced predators (such as kiore/rat and the kuri/dog. See Anderson, 1981; Holdaway, 1999; Greig and Rawlence, 2021, for different points of view on this).

With most of the actual living evidence gone, we now struggle with to understand how the dry forest system ‘worked’. In the wetter parts of New Zealand, peat has preserved the intact contents of moa gizzards. These show that the moa, at least just before they were bogged in a wetland, were browsing a range of twigs, leaves, and fruits (e.g. Burrows, 1980). In the drier country, there is little or no peat. Instead, some of the evidence lies in dried-out turds – ‘coprolites’ in polite parlance. Coprolites are a well-known source of information about what an animal ate. They are used today, for example, to see what introduced predators have been eating.

In New Zealand’s Central Otago dry country, a range of coprolites ‘morphologies’ have been found in dry rock overhangs, or ‘shelters’ (Wood and Wilmshurst, 2014). Some of the coprolites have been confirmed as moa by DNA, while others probably belong to other bird types. The moa coprolites contain leaf fragments (e.g. some from the shores of Lake Wakatipu, were found to contain Myrsine and a podocarp (what I would say was matai), pollen, Wood and Wilmshurst, 2013), and DNA (Wood et al., 2021). Put together, we now have a pretty good idea of diet (Wood et al., 2020 and references therein).

As part of my study focussing on ancient plant fragments in the rock shelters (Pole, 2022), I have come across a range of fossil coprolites too. The ones that were both large and had a silty (and now brick-like) texture, I considered to be moa. These were so hard that I could use a hack-saw blade to cut out a disk out from the middle of the coprolite. Then, with sand paper, I could abrade off a millimetre of so of the outside (No jokes about ‘polishing turds’ please, this is serious stuff). This was to minimise the chances that anything I found in next stage, might have simply been stuck on the outside when the coprolite was dropped on the shelter floor by the moa.

The next stage was to place the cleaned coprolite disk into warm water and peroxide. It would fizz a little, and soon broke down into a sludge of its constituent material. Under a microscope this proved to be mostly featureless fibres – probably the broken down remains of twigs. But in among that material, there were usually rare fragments of leaf cuticle. This is the translucent ‘skin’ of leaves, which retains an impression of the complex patterns of epidermal cells that it used to protect. These cuticle fragments were tiny, only a fraction of a square millimetre, and had very shredded appearance. But, even such small fragments often had the key characters which allowed them to be identified.

These fragments made it clear that at least some moa had eaten (among other plants) kōwhai (Sophora microphylla) leaves. This is interesting for a few reasons. Firstly, kōwhai foliage is somewhat poisonous. Today, kereru (our indigenous pigeon) seem to find it palatable, but little else in the bird world. So moa seem to have been another exception. Secondly, kōwhai has been suggested as something moa avoided (Wood et al., 2020). Thirdly, kōwhai seeds have something of a reputation among gardeners to be hard to germinate. It is often said that they ‘require scarification’ first. This can mean, for example, sanding the hard outside of the seed, or clipping it with nail clippers (I’ve also ben told, ‘Nah, just bury them deeply, and keep them slightly moist’).

At this point, a light might come on – so if moa ate kōwhai leaves, they probably ate the seeds as well. And since moa had crop-stones in their gizzards, as the seeds passed through the gut, they would definitely be ‘scarified’ and fit to germinate. And there we have it, a wonderful example of ecology – the kōwhai-consuming moa, an integral part of the kōwhai forest!

Unfortunately, this is probably just a nice-sounding story. A group of researchers (Carpenter, 2018; Carpenter et al., 2018) had a close look at how moa may have dispersed seeds. Their conclusion was that what went in one end of a moa, came out the other end in pretty bad shape (the bits of kōwhai leaf that I found, were often only the tougher parts that overlay the midvein). Basically, anything larger than about 3.3 mm was broken up. This includes kōwhai seeds, so it’s highly unlikely that any intact kōwhai seeds popped out of moa in their droppings.

In some ways, this is good news. Kōwhai trees do not need moa to perpetuate. In fact, this is obvious here and there in New Zealand’s dry country. Around some of the most ancient kōwhai trees, young ones are springing up. They are doing this from seed which is naturally germinating in the soil. This does not mean that moa were not an important part of kōwhai forests. Moa likely had a big impact on the forest structure. Their heavy foot-falls and browsing may have kept tracks and patches relatively open. Their presence may explain the ubiquitous mix of kōwhai and shrubby material found in the shelters.

I suspect that every plant type that moa hauled into the rock overhangs will eventually also be found to be part of their diet. This includes the almost ubiquitous kōwhai. Moa seem to have been remarkably unfussy eaters – everything from tough-as-hell native broom stems, to bush-lawyer with its thorns, went down the hatch. Compared with those, kōwhai foliage was relatively palatable. Despite its toxicity, moa gobbled it as well.

References

Anderson, A. 1981. Pre-European hunting dogs in the South Island, New Zealand. New Zeal. J. Arch. 3, 15-20.

Bunbury, M.M.E., Petchey, F., and Bickler, S.H. 2022. A new chronology for the Maori settlement of Aotearoa (NZ) and the potential role of climate change in demographic developments. PNAS, 119: 46, e2207609119.

Burrows, C.J. 1980. Some empirical information concerning the diet of moas. New Zealand Journal of Ecology, 3: 125-130.

Carpenter, J.K. 2018. Despite living amongst plants with large seeds, extinct giant moa dispersed only tiny seeds. The Conversation.

Carpenter, J.K., Wood J.R., Wilmshurst J.M., and Kelly D. 2018. An avian seed dispersal paradox: New Zealand’s extinct megafaunal birds did not disperse large seeds. Proc. R. Soc. B, 285: 20180352. http://dx.doi.org/10.1098/rspb.2018.0352

Greig, K. and Rawlence, N.J. 2021. The Contribution of Kurī (Polynesian Dog) to the Ecological Impacts of the Human Settlement of Aotearoa New Zealand. Frontiers in Ecology and Evolution, 9: https://doi.org/10.3389/fevo.2021.757988.

Holdaway, R.N. 1999. Introduced predators and avifaunal extinction in New Zealand. In: MacPhee, R.D.E. (ed.) Extinctions in Near Time. Springer, pp. 189-238.

Mulrooney, M.A., Bickler, S.H., Allen, M.S., and Ladefoged, T. N. 2011. High-precision dating of colonization and settlement in East Polynesia. PNAS, 108: E192–E194.

Perry, G.L.W., Wilmshurst, J.M., McGlone, M.S., McWethy, D.B., and Whitlock, C. 2012. Explaining fire-driven landscape transformation during the Initial Burning Period of New Zealand’s prehistory. Global Change Biology, 18: 1609–1621.

Pole, M. 2022. A vanished ecosystem: Sophora microphylla (Kōwhai) dominated forest recorded in mid-late Holocene rock shelters in Central Otago, New Zealand. Palaeontologia Electronica, 25(1):a1. https://doi.org/10.26879/1169
palaeo-electronica.org/content/2022/3503-vanished-ecosystem

Wilmshurst, J. M., Hunt, T. L., Lipo, C. P., and Anderson, A. J. 2011. High-precision radiocarbon dating shows recent and rapid initial human colonization of East Polynesia. . Proceedings of the National Academy of Sciences of the United States of America, 108: 1815-1820. http://doi.org/1810.1073/pnas.1015876108.

Wood, J.R. and Wilmshurst, J.M. 2013. Pollen analysis of coprolites reveals dietary details of heavy-footed moa (Pachyornis elephantopus) and coastal moa (Euryapteryx curtus) from Central Otago. New Zealand Journal of Ecology, 37: 151-155.

Wood, J.R. and Wilmshurst, J.M. 2014. Late Quaternary terrestrial vertebrate coprolites from New Zealand. Quaternary Science Reviews, 98: 33-44. http://dx.doi.org/10.1016/j.quascirev.2014.1005.1020

Wood, J.R., Richardson, S.J., McGlone, M.S., and Wilmshurst, J.M. 2020. The diets of moa (Aves: Dinornithiformes). New Zealand Journal of Ecology, 44: 1-21 https://dx.doi.org/10.20417/nzjecol.20444.20413.

Wood, J.R., Vermeulen, M.J., Bolstridge, N., Briden, S., Cole, T.L., Rivera-Perez, J., Shepherd, L.D. Rawlence, N.J., Wilmshurst, J.M. 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. https://doi.org/106910.101016/j.quascirev.102021.106992

Worthy, T.H., and Holdaway, R.N. 2002. Lost World of the Moa. Canterbury University Press, Christchurch.