What lives inside a 200 million-year-old reptile?

Sunday, 12 July 2026

Brainwaves is a new weekly Post and Sunday Star-Times feature showcasing the best, brightest and most innovative minds in New Zealand. Each week we will bring you four pieces of research from each of the country’s top universities - the articles will cover a broad range of disciplines and topics as both a window into what Kiwis are working on, and a showcase of how we can mould the future through inventive thinking.

It's incredible that Aotearoa New Zealand’s tuatara has outlived the dinosaurs. What’s equally amazing is what’s inside this special creature’s gut.

When most people think about tuatara, they think of them as living fossils. These unique creatures have been around for more than 200 million years, outlasting the dinosaurs. And no, they’re not lizards.

I study the microbiome, the community of microbes that live in the digestive system and, for my doctoral research, I wanted to know what was living inside the tuatara’s gut. These microbes help animals digest food, fight disease and respond to environmental change. As such unique, long-living animals, I was interested to find out if their microbes would be as special as the tuatara itself.

To find out, I travelled across Aotearoa, from warm northern sanctuaries to cooler southern sites, collecting samples from tuatara populations living in very different environments.

This meant getting very up close and personal with them.

I’m actually a bit of a germophobe, which makes this next part slightly ironic, because for my research I collected more than 200 samples by swabbing the tuatara’s cloaca, the opening to the digestive tract.

Back in the lab, we extracted DNA from those samples and focused on a gene shared by all bacteria. It works a bit like a barcode, letting us identify which microbes are present based on small differences in the sequence.

What I found was surprising.

A large portion of the microbes in tuatara doesn’t match anything we’ve seen in other reptiles. That means these microbes might be unique to tuatara, or to Aotearoa. Most reptiles are dominated by a group of bacteria called Bacteroides, a bacteria found across the animal kingdom, including in humans. Tuatara have very little of it, and their microbial community looks completely different.

To put that in context, we compared our data with microbiomes from 785 individuals across 91 reptile species. Tuatara were clearly doing their own thing. What that uniqueness means for the ecology and evolution of tuatara is something we still don’t know.

But the most unexpected finding was how stable their microbiome is.

No matter where I sampled, north or south, wild or captive, tuatara shared a consistent core microbiome. Even when their diet changed, or when they were moved into captivity, those microbial communities stayed largely intact.

That stability is encouraging for conservation. Tuatara are sometimes moved from offshore islands to mainland sanctuaries, which exposes them to new conditions. What my research shows is that these moves aren’t disrupting their microbiome. They seem to be remarkably resilient wherever they’re placed.

That doesn’t mean they’re unaffected by change.

When I compared populations across the country, I found that warmer temperatures were linked to differences in gut bacteria, as well as differences in body condition. Seasonal shifts also had measurable effects on the microbiome.

This matters because tuatara are vulnerable to rising temperatures. The temperature of their nests determines the sex of their offspring, with warmer conditions producing more males. Climate change could eventually skew populations in that direction, while also influencing the microbes that help keep them healthy.

Interestingly, diet had much less impact than we expected.

Tuatara are generalist insectivores. They’ll eat almost anything, although beetles seem to be a favourite. Even when their diet changes, their microbiome barely shifts.

We’re starting to realise that these microbial communities could be a powerful tool for conservation. By monitoring the microbiome, we may be able to track the health of tuatara populations and make better decisions about where and how to manage them.

For me, this project was about more than just the science.

I travelled all over Aotearoa, measuring gut communities, body condition and parasitism across multiple sanctuaries, and worked alongside mana whenua and other researchers in the field. It gave me a much deeper appreciation of both the species and the people who care for them.

I don’t miss crawling around in the bush at 2am getting covered in spiders, but I do think there is something incredible about the idea that after 200 million years, tuatara are still holding onto secrets.

And some of the most important ones are the ones we cannot see.

Professor Mike Taylor (University of Auckland), Professor Nicky Nelson (Victoria University of Wellington) and Dr Danielle Middleton (Bioeconomy Science Institute) supervised Cam Hoffbeck’s research.