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A lasting impression

Map of New Zealand overlaid on a photo of a beach cliffside

On the 27th of March 2022, the weekend after a large storm hit the Auckland region, Matthew Brown and Ava Peters made an unexpected discovery in South Head, Kaipara – a couple of hours drive north-west from Auckland CBD. The couple came across a large piece of sandstone that had slipped down from the cliff above, displaying the footprints of a large bird. Only one bird in Aotearoa could have left footprints quite that large, a moa.

 

Blog by Ricky-Lee Erickson (Auckland War Memorial Museum Tāmaki Paenga Hira), Daniel B Thomas (University of Auckland, Massey University), Kane Fleury (Otago Museum), Malcolm Paterson (Ngā Maunga Whakahī o Kaipara Ngahere Ltd.) and Bruce W. Hayward (Geomarine Research).

Moa were large, flightless birds, endemic to Aotearoa and were represented by nine species at the time of human settlement1. Moa varied greatly in size, with adults from the smallest species being slightly taller than a large turkey, through to adults from the largest species being taller than an Asian elephant.  The ranges held by different moa species also varied in size, with the smallest moa species being found across the Te Ika a Maui (North Island) and Te Wai Pounamu (South Island), through to there being separate giant species for the two main islands of Aotearoa2,3,4. The currently recognized Moa families were estimated to have originated 5-8.5 million years ago, with all 9 species estimated to have originated within the last two million years1. Moa are studied through archaeological remains, like bones, eggshells, coprolites (fossilised poo), feathers, mummified skin and footprints, as well as through mātauranga (Māori knowledge and oral traditions)5,6,7,8,9,10.   

Moa footprints imprinted on a beach rock
Moa Footprints in sandstone at beach

The sandstone block at South Head was perfectly positioned on the beach to display its three and a half positive casts, as well as a smaller separate block with a single footprint impression. It was quite incredible that they weren’t destroyed on the 8 meter fall down the cliff, and that they were spotted on what is quite a remote beach. 

Fossil trackways offer rare insight into the movement of ancient animals, providing ecological knowledge and insight on human-wildlife interactions.24 Kōrero tuku iho (Māori tradition) confirms ancestral knowledge of and direct experiences with moa to the end of the 17th century. Locally in South Kaipara, they are referred to as kura (nui) and te manu pouturu (the bird on stilts)11. Ancient names applied to the South Kaipara landscape recall interactions with moa (e.g. Te Toremingamoa, where swamp moa were driven and killed). Poka (trap pits) may still be found locally12,13.

Working to relocate footprints before damage occurs

Meanwhile, in March 2022: Matthew and Ava alerted Auckland War Memorial Museum, Tāmaki Paenga Hira, who in turn contacted Ngāti Whātua o Kaipara, the kaitiaki of the South Kaipara region. 24-hour surveillance of the footprints was quickly instigated, to ensure the protection and safety of this incredible find. Staff from Auckland Museum, representatives from Ngāti Whātua, palaeontologists and geologists worked together to come up with a plan to retrieve the footprints and bring them to a secure location, to be cared for by Ngāti Whātua o Kaipara. Retaining taonga within the rohe preserves the connection with the whenua (land) and provides direct access to taonga by mana whenua for education and research.

The team worked quickly to formulate a plan. The bottom of the sandstone boulder was submerged during high tide, meaning that each time the tide came in, the lower footprints were damaged. Eventually, the sandstone would crumble away to sand, and the footprints would be lost. So, it was decided that an excavation should be attempted, despite the considerable risk that the sandstone would crumble during the process.

Footprint Photogrammetry

While the team was formulating a retrieval plan, Dr Bruce Hayward studied the geology of the site and put together a report of his findings, giving the team more insight into the age of the sandstone and when the footprints were made. Dr Hayward deduced that for the footprints to be so well preserved in sandstone, they need to have been made in damp firm sand and then been filled and buried by windblown dry sand before they could be submerged by the tides that would have destroyed them14. Dr Hayward estimated the age of the sandstone to be 1 ± 0.5 million years old (Early-Middle Pleistocene era) using known relationships between rock layers across the Kaipara region15,16,17.

In addition, Dr Daniel Thomas undertook photogrammetry on the block containing the footprints, where it stood on the beach. Photogrammetry involves taking a series of images that can be stitched together to form a digital image. This ensured that at least a digital copy of the moa footprints could be preserved, in the event the excavation failed. The Museum’s Natural Science team also gathered comprehensive measurements of the footprints, and the distances between the footprints.

Planning relocation of the sandstone

After a few days of brainstorming and pulling resources, the team met at South Head to attempt to excavate the footprints. As the tide dropped enough to access the site, the team worked hard to isolate the footprints from the larger block, which was far too large to remove in one piece (roughly 2m2 in size and weighing 2-3 tonnes). After the block was trimmed down, it still took six people to carry! As the tide rapidly approached, the sandstone block was placed on a ute trailer and driven off the beach just as the water started to creep towards the tyres, it could not have been a narrower escape! Long after the sun had set, the team held a karakia to welcome the footprints to their new whare and congratulated each other on a successful day.

In the proceeding weeks, the team monitored the sandstone anxiously, to see if it was stable after the excavation. The facility was kept at stable temperature and humidity to ensure the block would not dry out too quickly. The footprints, which are exposed on the face of a block of quartz sandstone, is extremely friable and weakly consolidated (i.e. very crumbly). In fact, during the excavation, the main block was split into two separate pieces, realising the team’s fears. Luckily, the split occurred between footprints, with just the far tip of one of the prints damaged. Dr Thomas 3D scanned the footprints, which provided a more detailed digital copy of the block (compared to the photogrammetry method he used on the beach). It also gave the team a good baseline for how the footprints looked post-excavation and can be used by researchers in the future. The sandstone blocks have been stable in their new location and will soon be consolidated by preparators from the Queensland Museum.

Next, the team wanted to figure out what kind of moa made the footprints, how big was the moa and how fast was it travelling? To help with this, they looked to Auckland Museum’s existing moa skeleton collection for size comparisons and used a series of calculations in scientific papers that use the size and shape of footprints to deduce information on the animal that made them18.

 

We know that all four North Island moa species were present in the Auckland region during the last few thousand years19. These were the Moariki | Little bush moa, Kuranui | North Island giant moa, Moa hakahaka | Stout-legged moa and Moa ruarangi | Mantell’s moa. However, recall that the Kaipara footprints were likely formed 1 ± 0.5 million years ago. It is possible that the species of moa that made the footprints is an ancestor to the nine recognised species. Moa are reported as one of the most dramatic examples of morphological radiation amongst vertebrates20,21. This means that moa evolved very quickly and dramatically. Nevertheless, it was still useful to compare the moa footprints with more recent skeletons.

 

Using a series of calculations, the team estimated that the moa that left these footprints in South Head, roughly 1 million years ago, had a hip height of approximately 81.4 cm, weighed 13.8 - 29 kg (average weight of a 10-year-old human) and was moving at a pace of around 1.7 km per hour. This is slower than the walking pace of most humans and slower than the preferred walking speed for emus and ostriches22,23. This moa was enjoying a very leisurely stroll on the beach!

After generating a good idea of the sizes of North Island moa feet using Auckland Museum's collection, they were compared to the Kaipara footprints. Perplexingly, the measurements from the footprints did not perfectly match any of the four North Island moa. The toe lengths were very similar to the Mantell’s moa, too small for the Little bush moa or North Island giant moa and too large for the Stout-legged moa. However, the width of the foot was much larger than the three smaller moa (Mantell’s, Little Bush and Stout-legged), but too small to be an adult North Island giant moa. And so, we cannot say which species of moa created these footprints, perhaps it’s an ancestor of one of the four North Island species. Perhaps, it wasn’t quite fully grown, or simply an anomaly. We do know that this moa was relatively small and walking at a gentle pace across the beach of an ancestral Kaipara Harbour.

 

This find is particularly special because there are relatively few physical records of moa from the Kaipara region compared to other parts of Aotearoa. Within the collections of Auckland War Memorial Museum Tāmaki Paenga Hira, there are six moa specimens from the northern Kaipara region: bones from the Little Bush moa and four records of gizzard stones, not attributed to a species. Gizzard stones are rocks that birds eat on purpose, to help break up food in their stomachs. There is also one other record of fossil footprints in sandstone at Muriwai. The absence of moa records in South Kaipara and Auckland region is more likely due to the conditions not being suitable for preservation, rather than being about the original distributions or sizes of moa populations19.

 

The team is continuing to work with specialist preparators from Queensland Museum to preserve the footprints so they can be enjoyed and researched for years to come.

Acknowledgements

We would like to thank the team involved in the successful excavation of the prints:

  • Matt Rayner – Senior Researcher, Natural Sciences, Tāmaki Paenga Hira Auckland War Memorial Museum
  • Daniel Thomas – Honorary Academic, School of Biological Sciences, University of Auckland & Research Associate, Tāmaki Paenga Hira Auckland War Memorial Museum
  • Simone Giovanardi – Doctor of Philosophy, Massey University
  • Malcolm Patterson – Tumuaki, Ngā Maunga Whakahii o Kaipara, Ngāti Whātua o Kaipara
  • Fraserina Panui – Ngāti Whātua o Kaipara / Ngā Maunga Whakahii o Kaipara
  • Hemi Garland - Ngāti Whātua o Kaipara / Ngā Maunga Whakahii o Kaipara
  • Wikiriwhi Ratima - Ngāti Whātua o Kaipara / Ngā Maunga Whakahii o Kaipara
  • Tūmanako Povey - Ngāti Whātua o Kaipara / Ngā Maunga Whakahii o Kaipara
  • Davin Paterson - Ngāti Whātua o Kaipara / Ngā Maunga Whakahii o Kaipara
  • Ged Wiren – Collection care, Tāmaki Paenga Hira Auckland War Memorial Museum
  • Andrew Shaw - Collection Manager, Collection Care, Tāmaki Paenga Hira Auckland War Memorial Museum
  • Ricky-Lee Erickson – Collection Manager, Land Vertebrates, Tāmaki Paenga Hira Auckland War Memorial Museum
  • Rebecca Bray – Manager Natural Sciences Collections, Tāmaki Paenga Hira Auckland War Memorial Museum
  • Christina Bloom – Geo-heritage expert, Auckland Council
  • Jennifer Carol – Photographer and Media Producer, Tāmaki Paenga Hira Auckland War Memorial Museum

 

We would also like to thank the following individuals for their support of the project:

  • Josie Galbraith – Curator, Land Vertebrates, Tāmaki Paenga Hira Auckland War Memorial Museum
  • Sarah Withers – Associate Curator, Land Vertebrates, Tāmaki Paenga Hira Auckland War Memorial Museum
  • Fraserina Panui - Ngāti Whātua o Kaipara / Ngā Maunga Whakahii o Kaipara
  • Margaret Kapea - Ngāti Whātua o Kaipara / Ngā Maunga Whakahii o Kaipara
  • Hemi Garland - Ngāti Whātua o Kaipara / Ngā Maunga Whakahii o Kaipara
  • Tūmanako Povey - Ngāti Whātua o Kaipara / Ngā Maunga Whakahii o Kaipara
  • Malcolm Paterson - Ngāti Whātua o Kaipara / Ngā Maunga Whakahii o Kaipara
  • Davin Paterson - Ngāti Whātua o Kaipara / Ngā Maunga Whakahii o Kaipara
  • Wikiriwhi Ratima - Ngāti Whātua o Kaipara / Ngā Maunga Whakahii o Kaipara
  • Nicola Railton – He Korahi Māori Manager, Tāmaki Paenga Hira Auckland War Memorial Museum
  • Josie Maskell – Trust and Grants Development Executive, Tāmaki Paenga Hira Auckland War Memorial Museum
  • Natalie Edwards – Development Manager, Tāmaki Paenga Hira Auckland War Memorial Museum
  • Thomas Trnski – Head of Natural Sciences, Tāmaki Paenga Hira Auckland War Memorial Museum
  • Richard Ng – Senior Photographer and Media Producer, Tāmaki Paenga Hira Auckland War Memorial Museum
  • Alison Douglas – Preparator Biodiversity – Queensland Museum Kurilpa
  • Joanne Wilkinson – Preparator Geosciences - Queensland Museum Kurilpa
  • Brigid Gallagher – Conservator

 

Funding Sources:

  • The Tennyson Trust
  • Tāmaki Paenga Hira Auckland War Memorial Museum

 

References

 

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  2. Turvey ST, Holdaway RN 2005. Postnatal ontogeny, population structure, and extinction of the giant moa Dinornis. Journal of Morphology 265: 70–86.
  3. Latham ADM, Latham MC, Wilmshurst JM, Forsyth DM, Gormley AM, Pech RP, Perry GLW, Wood JR 2020. A refined model of body mass and population density in flightless birds reconciles extreme bimodal population estimates for extinct moa. Ecography 43: 353–364.
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