Research

Leach's Giant Gecko Rhacodactylus lechianus

Conservation status: Vulnerable

Description: A large species of gecko growing to a body length of 255 mm and tail approximately as long as the body when young, but nearly always small in adults. It has broad toes with extensive webbing, and extensive loose folds of skin along the ventrolateral margin of the body. The colour pattern highly variable, being typically greyish-green, through to brown, with lighter spots or pale blotches on the body.

Natural distribution: Widespread throughout New Caledonia over a wide altitudinal range, also present on satellite islands of Ile des Pins,

Distribution within Province Sud: Recorded from seven locations in the south of the Province, from Ile des Pins and several offshore islands.

Distribution within Province Nord: Recorded from a number of locations up the east coast with several records from the central mountain chain.

Threats:

• extremely high level of threat to insular populations (Isle of Pines and surrounding islets) posed by collection for illegal trade
• high level of threat to populations inhabiting low elevation closed forest at the base of the ranges on the west coast through loss of closed forest to ranching and agriculture, resulting in a decline in area of occupancy, and degradation and fragmentation of once continuous forest habitat
• high level of threat from exotic pests such as rats and cats (predation of adults, young and eggs), particularly in closed forest habitat adjacent to intensive settlement or urban development, small remnant forest patches, or islets off the Isle of Pines
• potentially high level of threat to populations in low elevation closed forest from high infestation levels of introduced fire ants (Wasmannia auropunctata), leading to a possible decline in abundance
• moderate level of threat to populations inhabiting low elevation closed forest on the east coast populations through loss of closed forest to subsistence agriculture, resulting in a decline in area of occupancy, and degradation and fragmentation of once continuous lowland forest habita
• moderate level of threat to the area, extent and quality of closed forest habitat and its edge through repeated firing of adjacent savannah habitat
• localised but moderate level of threat to populations inhabiting closed forest adjacent to urban development from general degradation of the forest, increased likelihood of fire in adjacent habitats, and increased pressure from pests and predators, resulting in an overall decline in area, extent and quality of habitat
• localised but moderate to high level of threat to populations inhabiting closed forest habitat exploited for timber plantations and logging resulting in a decline in area, extent and quality of mid elevation forest
• localised but potentially intensive decline resulting from collection for illegal trade at readily accessible sites

Conservation status: The species is recorded from 9 locations in the south of the main island (including 2 from the Ile des Pins - the status of which is uncertain) representing 5 disjunct sub-populations, and 14 locations in the central and northern areas of the main island representing around 9 sub-populations. Although the species does not satisfy the criteria for a small distribution (area of occupancy <1000km2), its large size and unique biology represent a special conservation case, and it is here categorised as Vulnerable.

Future research required:

• determine basic life history parameters and habitat requirements
• undertake targeted survey work to more comprehensively document the species overall distribution
• identify distinct geographic units
• undertake targeted survey work on the sub-population on the Isle of Pines to determine its preferred habitat on the island and the extent of threat posed by land clearing on the preferred habitat
• determine the levels of infestation of introduced fire ants at low elevation sites, particularly the island sub-populations, and monitor population trends for the species at these locations

Copyright © Australian Museum, 2002