Tuatara nest has scientists shellshocked

The Otago tuatara are protected by a predator-proof fence. Photo / Christine Cornege

Tuatara have hatched in the wild in the South Island for possibly the first time in several hundred years, experts say.

Researchers from the University of Otago found evidence of tuatara eggs hatching in a nest at Orokonui Ecosanctuary, a 307ha site near Dunedin where native species are protected from predators by a specially constructed fence.

The Otago researchers found hatched tuatara eggs.

Wild populations of tuatara disappeared from the North and South Islands soon after the arrival of humans and predatory mammals.

But researcher Scott Jarvie discovered the tuatara eggs in a nest at Orokonui in late 2012, during the course of his PhD research monitoring tuatara at the sanctuary.

Researchers have since spent two years monitoring the fate of the eggs, which were laid in the soil.

Adult females were among the tuatara translocated to Orokonui Ecosanctuary from Takapourewa-Stephens Island in October 2012.

"At least two of the adult females must have been carrying shelled eggs when transferred, as they nested soon afterwards," research team member Dr Anne Besson said.

"On Stephens Island, eggs hatch about 11-16 months after laying, after one winter in the ground. But when we checked the eggs at Orokonui previously, at the end of the summer about 15 months after laying, the eggs were still incubating."

The researchers continued to check on the nests and, at the end of last month, they found an excavated nest contained three empty eggshells with the characteristic splits that hatchlings make to exit the shells. Some other eggs had collapsed and failed.

Research team leader Dr Alison Cree, an associate professor at the University of Otago, said the discovery provided the first indication that tuatara eggs could hatch after a "remarkable" two winters in the ground.

Sanctuary staff were looking forward to the hatchlings becoming more visible as adults in about 15 years' time.