Nangur skink

Common name: Nangur spiny skink; Nangur skink

Scientific name: Nangura spinosa

Family: Scincidae

Conservation status: This species is listed as Critically Endangered in Queensland (Nature Conservation Act 1992) and nationally (Environment Protection and Biodiversity Conservation Act 1999).

Description and discovery: The Nangur spiny skink grows to about 19 cm with a snout to vent length of approximately 9.5 cm. Adults can weigh between 18 and 37 grams with new-born skinks weighing less than 1.5 grams. It has spiny scales along its back, tail, and flanks. It is brown in colour with dark irregular bands (sometimes quite faded) on its back. The belly is cream with the scales around its mouth barred with cream and brown.

The Nangur spiny skink was first discovered in 1992 at a single location in South East Queensland, with a second population found approximately 40km to the west in 1997. At the time, there was significant excitement that a skink so morphologically distinct had remained undiscovered for so long in South East Queensland.

Habitat and distribution

This skink is only known from South East Queensland, where it mainly occurs in semi-evergreen vine thicket and vine forest. It occurs at only two locations and genetic analysis indicates these populations became isolated from each other well over one million years ago, despite being only 40 kilometres apart.

Early surveys of the population of the first discovered population, estimated this population to be approximately 140 animals but is currently estimated to be less than 50 adults occupying an area covering less than 50 hectares. Monitoring of this population has observed a decline over the past decade with a 67% decline in animals between 2015/16 and 2019. Since 2019 the rate of decline has reduced with positive signs of the population slowly recovering with good numbers of immature animals detected during monitoring.

While recruitment into the population is encouraging, the adult population continues a slow decline. The reasons behind this decline are unclear but are believed to be due to a combination of the threatening processes described below. While recovery actions have been put in place to protect these animals including predator control and exclusion, weed control and fire management, the decline has continued and there may be other, yet unknown, reasons for this decline.

Current population estimates of the second population, indicate that there are a few thousand adult skinks over an area of approximately 850 hectares, with this population considered to be relatively stable with only small declines occurring on the margins of the population.

Extensive surveys in potential habitat at over 30 other locations have failed to find further populations. It is also currently absent from significant tracts of what appears to be suitable habitat at the two known locations.

Life history and behaviour

The Nangur spiny skink lives in a single-entrance burrow, normally occupied by one adult, but on occasion shared with another adult and/or juveniles. Burrows are typically constructed under a structure such as a rock or tree root and are relatively shallow, being less than 60 cm in length.

In the warmer months, the skink can be active at or near its burrow entrance any time from the pre-dawn twilight through to the post-sunset twilight. Activity peaks during the twilight periods when invertebrate activity is highest. Their home range around a burrow is unknown, however movement data from cameras monitoring burrows indicate that they spend most of their time either at or within a metre of the entrance with occasional longer forays. With this activity being focused close to the burrow entrance it often creates a smooth, distinctive platform in front of the burrow. Their diet includes a range of insect and arthropods such as beetles, spiders, slaters and other bugs.

The birth of 1-4 live young usually occurs between late January and into February and females have the capacity to breed every year. Mating has been seen to occur in the two to three months immediately following the birth of young, with gestation being around 11 to 12 months. It is unknown how long they live or at what age animals become sexually mature.

Threatening processes

There are a number of historic, current, emerging and potential threatening processes that are likely to impact the Nangur spiny skink. Understanding the extent of the impact and the role the threat has played in the decline of the species requires further research.

The following threatening processes are believed or known to have an impact on the Nangur spiny skink:

• Predation by feral cats, foxes, and pigs;
• Feral pigs, deer, and goats modifying and destroying habitat;
• Cane toads block borrows, compete with skinks for food resources and potentially prey on young animals;
• Invasion of ecosystem modifying weeds such as cat’s claw creeper (Macfadyena unguis-cati), coral berry (Rivinia humilis), lantana (Lantana camara) and high biomass grasses leading to significant habitat degradation, increased fire risk and changes to forest structure and microclimate;
• Climate change where the skink occurs will result in higher temperatures, an increase in the duration of hot weather and a likely reduction in rainfall. This will impact habitat quality and feeding resources, and increase the risk of uncontrolled fire burning into areas of dry rainforest that are sensitive to fire. Data already indicates a drying trend for both national parks where the species occurs, and wildfires in 2019 and 2020 burnt vine forest and threatened the second Nangur spiny skink population;
• Illegal collection and/or disturbance of burrow sites to obtain photographs;
• The introduction of disease with the emergence of several potentially fatal reptile diseases in Australia;
• Historic clearing of suitable habitat for agriculture and forestry;
• Historic harvesting and replanting of hoop pine plantations.

Recovery actions

A Recovery Plan for the Nangur spiny skink (Nangura spinosa) (PDF, 529KB) was prepared in 2010. However, new information on the species biology, population size and trajectories, and threats has been documented since the Recovery Plan was published and is being used to guide recovery actions.

The following recovery actions are currently being undertaken by the department:

• surveys to determine the population size and trajectory of both populations;
• implementation of threat abatement programs, including weed and feral animal control to protect both populations;
• implementation of fire management plans to protect the skink's habitat from fire;
• establishment of a captive breeding program.

Captive Breeding

With the on-going decline of the smaller population, captive breeding was identified as a priority recovery action. With little known about the breeding biology of the Nangur spiny skink, animals from the second and larger population were sourced for a pilot captive breeding program.

In late January 2020, 14 adults and one juvenile were collected and within a couple of weeks of being collected, three animals known to be pregnant had each given birth to twins, confirming the Nangur spiny skink bear live young. While these animals were the first Nangur spiny skinks born in captivity, they were not conceived in captivity.

Since the birth of these animals mating was observed amongst the adults and in January 2021, two sets of triplets and one set of twins were born, the first ever Nangur spiny skinks conceived and born in captivity.

The next step is to release animals born in captivity into the wild to determine if they can survive and be used to establish new populations or supplement existing populations.