Research

Marble-throated Skink Marmorosphax tricolour

Conservation status: Lower risk - least concern

Description: A moderately large species of skink growing to a body length of 66 mm, with moderately well developed limbs and a tail 150% of the body. Adult males differ markedly in colour and pattern to adult females and juveniles. Adult males are usually mid to light brown overall with russet along the sides, whereas females are typically two-toned being lighter above and darker with pale spotting at the sides. Both sexes have scattered dark markings on the underside of the body and throat, but these are more obvious in females. The scales of the body have three distinct keels.

Natural distribution: Widespread throughout New Caledonia, but with a scattered distribution on the west coast and ranges. The species is restricted to moist closed forest habitat and occurs over a broad latitudinal range.

Distribution within Province Sud: Recorded from a number of scattered sites within the Province, ranging from Kwa Neie in the south to Mt Sindoa, Plateau de Dogney, and Col de Rousettes in the north. It is known only from a few low elevation sites on the west coast. This most probably reflects both a lack of collecting effort and suitable moist forest.

Distribution within Province Nord: Recorded from a number of localities on the east coast and ranges, and from closed forest patches on the high ultramafic peaks down the north-west coast including Mt Kaala, Mt Kopeto, and Mt Toam.

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

Threats:

• potentially high level of threat to closed forest populations with high infestation levels of introduced Fire Ants (Wasmannia auropunctata) causing significant decline in abundance
• potentially high level of threat to isolated high elevation closed forest on ultramafic soils through activities associated with mining (particularly gully forests affected by mining spoil) resulting in a decline in area, extent and quality habitat
• potentially high level of threat to remnant closed forest populations on the northwest ranges from repeated firing of adjacent maquis habitat, resulting in a decline in area, extent, and quality of forest habitat
• low 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
• generally low level of threat to closed forest populations overall from repeated firing of adjacent savannah habitat, resulting in a decline in area, extent, and quality of forest edge habitat
• generally low level of threat from exotic pests such as rats and cats (predation of adults, young and eggs)

Maquis habitat - low and heath-like vegetation.

Conservation status: Marmorosphax tricolor occurs at over 35 sites across the entire length of the island, possibly representing up to 18 sub-populations. It is a closed forest-dependant species over most its range, and as such both the extent of occurrence and the extent and quality of habitat occupied are likely to be in decline. Because of its broad distribution, the species does not satisfy the criteria for area of occupancy or degree of fragmentation required to place it at a level of threat. As such it is most appropriate to categorise the species as lower risk - least concern.

Populations of Marmorosphax tricolor in the more highly developed lowlands areas of the west and east coasts are likely to be threatened at a local level by human activities.

Because of its specialised habitat requirements Marmorosphax tricolor is likely to occur as a number of disjunct sub-populations of varying sizes that reflect the level of fragmentation of closed forest habitat throughout its range. Broad levels of population sub-structuring have been observed in other closed forest dependant species. Marmorosphax tricolor may show similar levels of population sub-structure. Identification of these geographical units and preservation of the species across them is an important issue for conservation of biodiversity.

Future research required:

• identification of gaps in the distribution and surveying these areas to more comprehensively document the species overall distribution
• identification of distinct geographic units
• assess the extent of decline in area and/or quality of habitat of the closed forests in any geographical units identified above

Copyright © Australian Museum, 2002