Research

Short-snouted Giant Gecko Rhacodactylus chahoua

Conservation status: Vulnerable

Description: A large species of gecko growing to a body length of 147mm with a tail approximately as long as the body. Moderately broad toes with extensive webbing, and loose folds of skin along the ventro-lateral margin of the body. The colour pattern highly variable, with a mottling of lichenous grey-green and white on browns of varying hues.

Natural distribution: Known from a few scattered locations on the main island, the Ile des Pins, and the Belep Islands.

Distribution within Province Sud: Recorded from the Ile des Pins in the late 1800's, Mt Mou in 1925, and recently from Sarramea at the base of Plateau de Dogney.

Distribution within Province Nord: Recorded from several locations in the Valle d'Amoa north of Poindimie, and recently from two locations in the north-west near Koumac, and the Belep Islands.

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
• high level of threat to isolated low elevation closed forest on the north west coast from clearing for ranching or agriculture resulting in degradation, loss, and further fragmentation of habitat
• high level of threat to populations in low elevation closed forest of river valleys on the east coast from clearing for subsistence agriculture resulting in degradation, loss and further fragmentation of habitat
• high level of threat to isolated low elevation closed forest on the north west through repeated firing of adjacent savannah habitat resulting in a decline in area, extent and quality of habitat
• potentially high level of threat from exotic pests such as rats and cats (predation of adults, young and eggs), particularly in forest habitat adjacent to urban development or intensive human settlement
• localised but potentially intensive decline resulting from collection for illegal trade at readily accessible sites
• localised but potentially intensive decline in area, extent and quality of closed forest habitat adjacent to urban development or intensive human settlement

Conservation status: Rhacodactylus chahoua is recorded from only two locations in the far north of the main island and the outlying Belep Islands, 5 locations across the southern and central areas of the main island, and another from Ile des Pins. These represent seven widely disjunct sub-populations with an area of occupancy <1000 km2. Recent field research has extended the species range in the north of the island, and the broad distribution of records indicates the species is more widespread than previously thought, however its distribution is still likely to remain as scattered isolated populations with a low overall area of occurrence.

Most recent records have been from low elevation forest, particularly riverine (near a river) or valley forest. Low elevation closed forest has been greatly reduced or modified through the activities of humans, both pre and post European occupation. Clearing for subsistence agriculture has severely impacted upon forest in coastal and near coastal areas of the east coast. Low elevation forest on the west coast has also undergone extensive alteration and disturbance by grazing activities. As such the species is likely to have already suffered a significant reduction in range, and to have a highly fragmented area of occupancy.

These factors in combination with the range of threats identified above, and the specialised biology of the species, indicate it can conservatively be categorised as Vulnerable, but could be moved to a higher level of conservation concern given the number and intensity of those threats.

Future research required:

• information on the species distribution and biology to determine basic life history parameters and habitat requirements
• assessment of the extent of decline in area and/or quality of sclerophyll forests and gallery forest habitat with regard to the impact of fire on the forest edge
• assessment and monitoring of the spread of fire ant on populations in sclerophyll forests and gallery forests

Copyright © Australian Museum, 2002