Robust skink breeding programme

New Zealand Herpetological Society robust skink breeding programme

Robust skinks (Oligosoma alani) are New Zealand's largest species of native skink, reaching over 30cm in length, and are now one of our rarest lizards. Like all other native lizards, they are endemic, meaning they are unique to NZ and found no-where else. The species was once common in lowland areas throughout the North Island, but due to the introduction of mammalian predators, the species is now found only on a handful of small offshore islands.

Unusually for a skink, robust skinks are nocturnal. They naturally occur in forested areas, usually hiding under rocks or logs, in deep leaf litter, or in seabird burrows during the day. At night, they emerge to forage for food which includes a wide variety of insects, and the berries from native trees and shrubs such as Coprosma and Kawakawa.

Due to their large size, nocturnal habits, terrestrial lifestyle, and slow life-history (usually taking 5-8 years to reach maturity, and females generally breeding only once every two years), they cannot survive in the presence of any introduced mammalian predators. In fact, robust skinks would have been among the first species to disappear from the mainland following the arrival of humans in New Zealand, and only survived on six small islands that fortunately have never had introduced mammals.

In order to safeguard the species for future generations, new populations should be established on other islands and in pest free areas where they will be safe from predators.

This sounds simple enough. However, the islands that robust skinks occur on are small, and as a consequence the populations on these islands are restricted both in number and genetic diversity. These skinks are in high demand for conservation and restoration projects, but we cannot collect large numbers of animals from existing populations to start new ones, as this could threaten their survival on these islands by critically reducing their numbers or genetic diversity. Because of this, a captive breeding program, providing sufficient numbers of animals for release into new areas, would be immensely valuable to assist robust skink conservation.

The New Zealand Herpetological Society (NZHS) members and Zoos hold a number of robust skinks in captivity. These skinks have been bred for several generations from wild caught animals that were collected around 50 years ago. In a partnership, the NZHS and Department of Conservation (DOC) have written a captive management plan for these animals, so that they can be bred in captivity for release into new safe areas.

Across their natural range, robust skinks are genetically distinct between island populations, and were collected from several different islands to start captive colonies. So, the first step for the robust skink captive programme is understanding what island/s the current captive individuals originated from, and assessing their suitability for a breeding program. Part of this will involve investigating the genetic diversity of the captive population, which may have originated from a small number of founders. The NZHS will work with Iwi partners in the event it is necessary to collect additional wild animals to supplement the genetic diversity of captive stock, or start breeding programs for different populations of robust skink.

Once the NZHS has this information, we can pair breeding animals and begin the programme.


Key Messages:

  • The NZHS are seeking an equal financial contribution from donors to enable the project to progress.
  • The NZHS wants to support robust skink conservation through establishing new populations in safe sites.
  • The NZHS will lead the captive programme by contributing skills, husbandry and facilities.
  • The NZHS will work in partnership with Iwi, DOC, and island managers to establish new, secure populations in the wild.
  • Currently, we have received a grant from the Lotteries Environment and Heritage fund to get the captive robust skinks DNA tested to understand their geographic origin and genetic diversity.
  • We intend to seek further funding in the future to support later stages in the project including such activities as; collection of additional animals if necessary, disease screening, and eventual releases.


Robust skinks, adult and juvenile
Adult robust skink with juvenile.
Photo: Nick Harker