Researchers at the University of Otago say they've found evidence of tuatara eggs hatching in a nest at the Orokonui Eco-sanctuary near Dunedin.
Tuatara disappeared from the mainland North and South Islands shortly after the arrival of humans and mammals, and previously survived only on offshore islands.
Researchers have been monitoring the pregnant adult females who laid eggs not long after they arrived at the sanctuary three years ago.
It has a specially-constructed fence to protect the tuatara, brought from Stephens Island, and other native animals from introduced mammals.
"At least two of the adult females must have been carrying shelled eggs when transferred, as they nested soon afterwards," said Dr Anne Besson, a member of the research team.
The eggs are laid in the soil and hatch between 11 and 16 months later, after one winter in the ground.
At the end of last month, researchers found three empty eggshells with characteristic splits showing where the hatchlings had exited the shells. Others had collapsed and failed.
Associate Professor Dr Alison Cree, the research team leader, said the timing suggested that cool soil temperatures at the sanctuary could slow egg development.
"With New Zealand reptiles, you have to be in for the long haul, unlike many birds where nesting success may be apparent within a few weeks or months."
The hatchlings cannot yet be seen by the public, but will be more visible as adults in about 15 years time.