Research

Gracile Dwarf Skink Nannoscincus gracilis

Conservation status: Lower risk - near threatened

Description: A small, elongate species of skink growing to a body length of 45 mm with short limbs and digits, and a short tail approximately equal in length to the body. The scales of the body are smooth or have several weak grooves. Colouration is two-toned being lighter on top and darker at the sides.

Natural distribution: Nannoscincus gracilis is widely distributed throughout the central ranges but represented only by one or two isolated records in the far north and south of the island. It is not known whether the sub-populations in the far north and far south of the island are broadly disjunct from those on the central ranges. The lack of records in some areas most likely reflects inadequate survey work, but its absence in other well studies areas (Mt Panie) show that its distribution may be irregular. The species is generally restricted to moist forest habitat throughout its range. Its distribution reflects the pattern of fragmentation of closed forest habitat throughout its range, and as such will consist of a number of disjunct populations of varying size.

Distribution within Province Sud: Recorded from several ultramaffic peaks in the north of the Province (Mt Sidoa, Mt Do, Pic Ningua), several locations in the central ranges (Plateau de Dogney, Saramea, Me Adeo), and records from Noumea and Foret Thy.

Ultramafic - rocks that are dominated by minerals high in magnesium and iron, and which tend to be dark-coloured rather than pale.

Distribution within Province Nord: Recorded from several sites in the central ranges (Col d'Roussettes, Mt Aoupinie, Foret Plate), Poindimie, and Mt Mandjelia in the far north-east ranges.

Threats:

• potentially high level of threat to isolated high elevation closed forest populations on ultramafic soils in the central ranges through activities associated with mining (particularly gully forests affected by mining spoil) resulting in a decline in area, extent and quality of habitat
• moderate to potentially high level of threat to closed forest populations with high infestation levels of introduced Fire Ants (Wasmannia auropunctata) causing a significant decline in abundance
• moderate level of threat to low elevation closed forest on the east coast from clearing for subsistence agriculture resulting in loss and further fragmentation of habitat
• low level of threat to mid elevation forest for timber plantations resulting in a decline in area, extent and quality habitat
• low level of threat to populations on the east coast and ranges from repeated firing of adjacent savannah habitat resulting in a decline in area, extent and quality of closed forest edge habitat

Conservation status: Nannoscincus gracilis occurs at 19 sites representing up to 14 sub-populations. Because of its relatively broad distribution the species does not satisfy the criteria required to place it at a level of threat. It is also likely to be recorded from additional locations with further survey work. Most records are from the central ranges with broadly disjunct isolated sub-populations present in the far north and far south of the island. It is a closed forest-dependant species over most its range.

Although it has a relatively broad distribution and has been recorded from a number of sites, N. gracilis is categorised as lower risk - near threatened. The reason for this being the degree of fragmentation of closed forest habitat and wide range of potential threats leading to a decline in area, extent and/or quality of that habitat. In particular populations of N. gracilis in the more highly developed lowlands areas are likely to be threatened at a local level by human activities in these areas.

It is also possible the species will show broader levels of population sub-structuring. Identification of these broader geographical units and the threats at a local level, are important issues for the preservation of the species and for conservation of biodiversity.

Future research required:

• general survey work to more comprehensively document the species overall distribution, particularly in the north-east ranges and north-west massifs
• identification of distinct geographic units

Massif - a compact portion of a mountain range, containing one or more summits.

Copyright © Australian Museum, 2002