Research

Deplanche's Shiny Skink Sigaloseps deplanchei

Conservation status: Lower risk - near threatened

Description: A small species of skink growing to a body length of 46 mm with relatively short limbs, a short tail approximately 88-111% the length of the body, and smooth body scales. Colouration is light overall with a yellow flush to the ventral surface and orange on the throat of males.

Natural distribution: Widely distributed throughout the south the island.

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 a number of scattered sites in the far south to near Mt Ouin in the north, then only as scattered records further north including historic records from the Ngoye valley, and recent records from Mt Sidoa and Mt Menzai. The latter record is the most northern and is of particular interest as Mt Menzai is an outlier to the main southern ultramafic block. The sparse and scattered nature of the species distribution in the north of its range reflects both the lack of survey work and fragmentation of remnant closed forest in that area.

Because of its specialised habitat requirements its distribution will reflect the pattern of fragmentation of closed forest habitat throughout the species range, and as such will consist of a number of disjunct populations of varying size. Some populations, like those at Kwa Neie, Mt Sidoa and Mt Menzai, are clearly isolated from neighbouring populations by extensive areas of maquis shrubland.

Ultramafic - soils that are dominated by minerals high in magnesium and iron, and which tend to be dark-coloured rather than pale.
Maquis shrubland - low and heath-like vegetation

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
• moderate to 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
• moderate to high level of threat to closed forest edge through repeated firing of adjacent maquis shrubland habitat resulting in a decline in area, extent and quality of habitat
• low level of threat to populations in low elevation closed forest on the east coast from clearing for subsistence agriculture resulting in loss and further fragmentation of habitat

Conservation status: Sigaloseps deplanchei occurs at over 15 sites representing up to 10 sub-populations. Because of its broad distribution, the species does not satisfy the criteria for area of occupancy required to place it at a level of threat. It is also likely to be recorded from additional locations with further survey work. 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, S. deplanchei is categorised as lower risk - near threatened. The reason for this is, 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 S. deplanchei in isolated high elevation closed forest on ultramafic soils areas are likely to be highly threatened at a local level by activities associated with mining.

Geographic variation revealed in morphological studies may reflect different levels of population sub-structuring. Identification and preservation of these geographical units is an important issue for conservation of biodiversity.

Future research required:

• general survey work to more comprehensively document the species overall distribution
• identification of distinct geographic units
• assessment of the extent of decline in area and/or quality of forest habitat in which the species occurs

Copyright © Australian Museum, 2002