The ecosanctuary, north of Dunedin, is surrounded by a fence that keeps out introduced mammals, other than perhaps mice.
The hatchlings at Orokonui were found earlier this year under small strips of roofing material by Jade Christiansen, an undergraduate student working on a Te Ngaru Paewhenua: Māori and Pacific Science Summer Studentship at the University of Otago.
"My hands were shaking," Ms Christiansen said.
"I was very nervous, yet very excited.
"The hatchlings can be surprisingly lively. One of them still had its horny 'shell-breaker' - a projection on the tip of its snout - so I knew it had hatched recently."
Professor Alison Cree, of Otago's Department of Zoology, said evidence of offspring being produced was an important stage in re-establishing a viable population.
A breeding population at Orokonui could be a valuable contribution to protecting the survival of the taonga species in the global climate emergency, she said.
"We've been excited to see tuatara surviving and growing, and we've long suspected that hatching was occurring based on indirect evidence, including split eggshells. But this is the first direct evidence for the entire cycle through to hatching, from egg-yolk production onwards in the mother's body, taking place at Orokonui."
It was likely the hatchlings were female due to their long incubation period and the cool soil temperatures.
Nest temperatures when known to determine the sex of developing tuatara embryos.
Orokonui Ecosanctuary conservation manager Elton Smith said the discovery was a significant one for the sanctuary.
"This success can be directly attributed to our fence that excludes all introduced mammals that would otherwise predate upon the tuatara," he said.
Orokonui Ecosanctuary is currently closed due to the Covid-19 outbreak, but staff are still carrying out essential tasks.
- RNZ
