A revision of the threat status of New Zealand's reptiles has shown Otago and grand skinks have recovered dramatically in managed areas at Macraes Flat, while other populations continue to decline.
However, the recovery did not yet meet the threshold for their threat classification to change, a study in the New Zealand Journal of Zoology says.
The two species were among the six assessed as being at greatest risk of extinction (nationally critical) and all were from the South Island, in the study led by the Department of Conservation.
Grand and Otago Skink Recovery Programme chairwoman Prof Carolyn Burns, of the University of Otago, said she thoroughly agreed with the classification which considered the population had not yet progressed far enough to off-set the declines in other parts of the species' ranges.
Since the recovery programme had been in place, skink numbers had improved in managed situations such as within enclosures and areas were predators numbers were controlled.
"We're optimistic. It's good news they are showing a response."
The status of the population as a whole, particularly those which were not within those controlled areas remained in the high risk categories, she said.
Among those were skink populations in the west of the South Island which while the same species were genetically different, but not much was known about their status or range.
"We're very much in the dark."
They were hopeful they would be able to fulfil their long-term goal of re-establishing populations in the wild but in the meantime they need protection from predators, Prof Burns said.
Managing the populations was slow and expensive work due to the skinks slow reproductive rate.
The study said despite considering public submissions on Otago Peninsula's jewelled gecko suggesting it was taxonomically distinct, it listed as at risk - declining due to numerous records of the skinks in Canterbury and western Otago.
"Otago Peninsula represents only a small proportion of this species range."
While five species had improved their threat status in the past five years, the Mackenzie Basin and long-toed skink's status increased due to potential threats from rabbit-driven predator irruptions as well as the new threat of dairy conversion destroying habitat.
