What we found in Martinborough’s Cave of Bones

What we found in Martinborough’s Cave of Bones

Victoria University summer scholar Laura Wilson has spent two months sorting through a box of bones and dirt. The aim? To identify and catalogue the huge array of species represented in Martinborough’s Cave of Bones.

How many species do you think are in this box?

Samples - bones and dirt
The samples Alan came back from his expedition with. Photo by Rachael Hockridge. Te Papa

Three years ago, Curator Vertebrates Alan Tennyson retrieved this sample from a cave in Martinborough.

Even without cleaning, Alan could identify the beak of kākāpō, Finsch’s duck leg bones, and even a tuatara jaw.

It’s a huge amount of work to clean, sort, and identify species in a sample such as this – and it’s with the help of volunteers and summer scholars, such as Laura Wilson from Victoria University, that this work can happen.

Laura stands over bones sorted into different boxes
Laura with the bones from the cave, 2020. Photo by Rachael Hockridge. Te Papa

Cleaning, identifying, and sorting

Cleaning

Laura’s first step was to wash everything using water and a toothbrush – which took about a week due to the number of small fragments.

“This cave has been sampled for over 100 years, but people tended to only take the big bones, rather than the tiny ones,” she says. “So it was really important to represent small species properly this time around.

“I picked up everything that was bigger than 1mm by using a sieve with a really small mesh. This ensured that the tiny lizard and frog bones didn’t fall through the gaps with the rest of the crud.

“I also wanted to catch tiny flakes of bone, because we know they still have DNA in them that can be identified one day.”

Hands point to a large sieve
The sieve Laura used to clean the bones, 2020. Photo by Rachael Hockridge. Te Papa

After the cleaning and sieving, Laura removed the large pieces of bones, and then began to pick through tens of thousands of tiny pieces to decipher whether they were animal remains, seeds … “Anything worth keeping that gives a clearer picture of the cave environment,” she says.

Laura picking through tiny pieces
Laura picking through the pieces, 2020. Photo by Rachael Hockridge. Te Papa

Sorting

Laura then sorted everything into different elements to make it easier to compare bones when it came to identification.

She removed ones that are impossible to identify without DNA testing (like toes!). “I learnt so much about bird anatomy,” she says.

Bones sorted into boxes
Sorted bones, 2020. Photo by Rachael Hockridge. Te Papa

Identification

Laura then had the huge job of identifying the bones.

“I started out comparing with species previously found in the cave,” she says.

Vertebrate curator Alan Tennyson taught Laura how to identify species. This included identifying distinct features that different groups of birds have.

“You basically just hold up already identified bones until you get a match!” Laura says. “First, go by size, because the bigger bones can only be a certain number of things.”

Laura holds two similar looking bones
Laura holding two radius bones (left is a kākā, right is a Finch’s duck), 2020. Photo by Rachael Hockridge. Te Papa

The results

The results from the identification show that pretty much anything that fell in this cave couldn’t get out, Alan says.

“When you look at the make-up of the fauna it’s mostly flightless things,” he says.

Alan and Laura stand over a table of bones
Alan and Laura identifying bones, 2020. Photo by Rachael Hockridge. Te Papa

Laura and Alan have concluded that approximately 18 species were in this one box. This includes at least 13 species of bird and 41 individual birds.

Those species include:

  • 12 Finsch’s ducks
  • 6 weka
  • 5 kākāpō
  • 5 kiore (rats)
  • 4 Hodgens’ waterhens
  • 3 rowi kiwi
  • 2 North Island takahē/mōho
  • 2 snipe rails
  • 2 New Zealand coots
  • 2 tuatara
  • 1 paradise shelduck
  • 1 North Island adzebill
  • 1 owlet-nightjar
  • 1 bush wren
  • 1 North Island saddleback

In addition, Laura and Alan identified 4 gecko bones, 24 skink bones, and 25 frog bones.

And Mollusc expert Bruce Marshall identified 9 species of tiny native land snail.

“All the extinct flightless rails from the North Island are sitting right here,” Alan says. “And there are also so many Finsch’s ducks, presumably they were really common – which is possibly not what you’d expect in a native forest.”

Painting of a grey duck with a brown head
Finsch’s Duck Chenonetta finschi. From the series: Extinct Birds of New Zealand, 2004, Masterton, by Paul Martinson. Te Papa (2006-0010-1/32) CC BY-NC-ND 4.0.

Laura’s favourite species from the box is the owlet-nightjar. “I didn’t even know it existed before this!” she says.

Painting of a small owl (the owlet-nightjar)
New Zealand Owlet-nightjar Aegotheles novaezealandiae. From the series: Extinct Birds of New Zealand, 2004 by Paul Martinson. Te Papa (2006-0010-1/58) CC BY-NC-ND 4.0.

Alan’s highlights are the frog and lizard bones, because generally they don’t preserve as well as this.

“This particular site is perhaps the best site in New Zealand for getting DNA out of bones – it’s so well preserved. So these bones are so genetically valuable,” he says.

“I know there’re a few gems still in here that I need to identify. And even the pieces that are too small to identify, we’ll keep – there’s DNA in them and techniques these days which are really efficient. You can essentially run them though a machine and it will spit out their identities.”

Overall, Laura identified 740 bones. “122 of these were from animals like sheep though …” Laura says.

Hands hold tiny bones with a label that says 'skink'
Laura holds skink bones, 2020. Photo by Rachael Hockridge. Te Papa

Thanks to Laura for all her hard work and to Victoria University who we partner with for their Summer Research Scholarships initiative.

If you’re a student at VUW and would like to work on a project with Te Papa’s scientists, keep an eye out for the next call, which will happen in the second half of this year.

Further thanks

We’d also like to acknowledge Clint Easton, Andrew Veale, Kristina Aluzaite, and Sam Tennyson who helped collect this sample from the cave; also James Crampton at Victoria University for assisting with Laura’s supervision.

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