Kaipara Moa mystery: Footprints discovered at South Head likely one million years old

These moa tracks, discovered at Kaipara's Mosquito Beach three years ago, have been estimated to be around one million years old.

• A set of moa tracks, preserved on a fallen sandstone slab, were discovered by a couple walking along Kaipara’s Mosquito Beach in March 2022
• The slab and its precious contents were rescued after a multi-day salvage effort – and just as the tide was approaching
• Now, scientists have been able to describe the tracks’ likely age – but haven’t been able to nail down what moa species left them around one million years ago

It was the find of a lifetime: a slab of sandstone, freshly fallen from a cliff amid a heavy storm, bearing the unmistakably large footprints of our long-lost moa.

Just over three years later, scientists can now tell us much more about the prints that Ava Peters and Matthew Brown happened upon after a slip at Kaipara’s Mosquito Beach.

The couple, who’d been returning from an unsuccessful fishing trip, were stunned at the discovery and quickly alerted Auckland Museum, which in turn notified Ngāti Whātua o Kaipara.

When scientists arrived to find the tide approaching, they knew they were in a race against time to save the slab and its precious contents.

“We worked together for a few days to come up with a plan and materials required to attempt an excavation and kaitiaki watched over the footprints day and night,” said the museum’s land vertebrates collection manager, Ricky-Lee Erickson.

Moa tracks found on a fallen sandstone slab at Mosquito Beach, at Kaipara's South Head, are among just a handful of traces of moa discovered in the Auckland region. This image shows experts and kaitiaki working to salvage the slab after its discovery in March 2022. Photo / Auckland Museum

“We knew that the odds were against us, as the sandstone slab was extremely soft and friable, but we all agreed it was worth a shot.”

Each time the tide came in, the lower prints were submerged in water, eventually to be washed away.

Museum research associate Dr Daniel Thomas took a series of photographs that were digitally stitched together to create a 3D image of the tracks.

But fortunately, the team managed to rescue the two-tonne slab – which took six people to carry – just in time.

“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,” Erickson said.

Since being welcomed back to Ngā Maunga Whakahii o Kaipara, the block has been stored at the museum within a temperature and humidity-controlled room, enabling the prints to dry very slowly.

Along with consolidating the footprints so they’re not at risk of crumbling or cracking, scientists have also been able to date and describe them.

Prominent geologist Dr Bruce Hayward has estimated the prints were created around one million years ago – give or take 500,000 years – making them a standout artifact.

“There aren’t too many moa trace fossils, particularly from the Auckland Region and from the Early-Middle Pleistocene era,” Erickson said.

The museum housed just six moa specimens from the northern Kaipara region, along with one other record of fossil footprints in sandstone at Muriwai.

“This absence of moa fossils in south Kaipara and Auckland region is more likely due to the conditions not being suitable for preservation, rather than a reflection on the size and distribution of moa populations.”

A team of experts and kaitiaki helped save a fallen slab of sandstone, bearing million-year-old moa footprints, after it was discovered at Auckland's Mosquito Beach in March 2022. Photo / Auckland Museum

For the footprints to have been preserved, they’d have likely been made in damp, firm sand, before being filled and buried by windblown dry sand, then finally submerged by the tides.

That meant Mosquito Beach was probably still a sandy beach one million years ago, Erickson said.

Through close analysis of the footprints, researchers also determined the moa was around 80cm tall at the hip – a little shorter than a fully-grown emu – and at up to 29kg it may have weighed as much as a 10-year-old child.

They concluded the moa was walking at a leisurely 1.7km per hour at the time the prints were made: slower than the preferred walking pace of emus, ostriches and humans.

“So, all we can say is that this moa was enjoying a nice slow stroll on the beach in ancestral Kaipara.”

But there were still lingering questions the team have been unable to answer: namely, just what species they were dealing with.

Thomas suspected the prints were either left by a very large species like kuranui/North Island giant moa – or a previously undescribed species.

“These fossils are one million years old, give or take, so there might have been different species back then,” he said.

Another possibility was that it was one of the species present when humans first arrived in Aotearoa, but which was simply leaving footprints in a slightly different shape.

“We can stand on the beach where these footprints were found, and imagine these magnificent icons of our natural history gently plodding along,” Thomas said.

“The fact that we haven’t matched the footprint to a species reminds us that most of what we know about the history of moa comes from the time of people living in Aotearoa – and if we step only a little way deeper into time our level of knowledge about these magnificent birds falls away,” he said.

“Moa are often imagined as forest species, but was this a coastal moa foraging along a beach?

“This discovery has revealed that even a short trackway of four footprints can reveal a wealth of information about the ecology and biology of moa.”

Moa footprints discovered on a fallen slab of sandstone at Auckland's Mosquito Beach were estimated to be around one million years old. Image / Auckland Museum

A further mystery, Thomas said, was that one of the five embedded footprints didn’t match the others – meaning there could be a separate moa trackway still to be found.

For tangata whenua, the tracks represented something yet more profound.

“In our history, there are names, places, and remembered events that feature moa,” said Malcolm Paterson, of Ngā Maunga Whakahī o Kaipara.

“So even though these footprints come from a bird that was around before there were Homo sapiens, its descendants and our ancestors had some kind of relationship.

“We’ll never have a relationship with moa in that way again. There is a link between this bird’s descendants and our ancestors – and that’s a special relationship within the context of Aotearoa.”

Jamie Morton is a specialist in science and environmental reporting. He joined the Herald in 2011 and has written about everything from conservation and climate change to natural hazards and new technology.

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