Taxonomy
Common name :
Le Gecko géant à tête bossue
Knob-headed Giant Gecko Red List Status -
Least Concern (LC) , assessed in 11/12/2017Protected species -
in Southern Province , in Northern Province
Description
Description:
A large species of gecko growing to a body length of 125mm and with a tail up to 90% the length of the body; moderately broad toes; the head has a series of raised crests on the skull that give the gecko a "knobbed" or "horned" appearance; the colour pattern is highly variable, being mottled or having a light and dark broad stripes running down the body.
Natural Distribution:
Moderately widespread throughout the ultramafic ranges in the south of Grande Terre, and from isolated ultramafic peaks on the northwest coast.
Distribution within Province Sud: Widespread in the ultramafic ranges from the very south of the island north to Mt Do and Pic Ningua - there is a large gap in distribution between Mt Ouin and Pic Ningua, reflecting a lack of field surveys in maquis habitat in this area.
Distribution within Province Nord: Recorded from ultramafic peaks in the southeast of the Province and on the northwest coast south to Massif du Boulinda, and isolated low elevation maquis sites.
Habitat:
Maquis shrubland ranging from low open maquis to maquis preforestier; edge of humid forest habitat.
Threats:
-
high level of threat to maquis habitat through repeated firing resulting in a decline in quality of habitat through simplification of plant diversity and vegetative structure.
-
potentially high level of threat to maquis and humid forest edge habitat on ultramafics through loss or degradation of habitat from activities associated with mining.
-
potentially high level of threat to populations in humid forest edge habitat from high infestation levels of the introduced Little Red Fire Ant (Wasmannia auropunctata) ), resulting in a significant decline in abundance particularly at low elevation.
-
localised but potentially high level of threat from exotic pests such as rats, cats and pigs (predation of adults, young & eggs) in heavily affected localities, particularly adjacent to development.
-
localised but potentially high level of threat by the collection for illegal trade at readily accessible sites.
Conservation Status:
Lower Risk - least concern.
Rhacodactylus auriculatus occurs at more than 20 locations. The species widespread distribution throughout maquis shrubland over the south of the island indicates there is likely to be some connectivity between the subpopulations identified, and therefore the potential for re-colonisation if it becomes locally extinct.
Threats leading to a continuing decline of humid forest edge habitat and maquis shrubland have been identified, but large areas of potentially suitable habitat subject only to minimal or no disturbance occur within the species range. For this reasons Rhacodactylus auriculatus is most appropriately categorised as Lower Risk – least concern. The species is not considered to be under any overall immediate threat, but sub-populations in some regions (particularly in the vicinity of mining activities) could be subject a suite of moderate to high localised threats.
Listed as Least Concern in view of its wide distribution, presumed large population, and because the rate of population decline is not sufficient for it to be considered under a higher threat category. Even though the extent of occurrence is <20,000 km², the population is significantly greater than 10,000 individuals, the reduction in population size is expected to be <30% and the species is present at >10 locations.
Geographical area
This species is endemic to New Caledonia. It is widespread in southern Grande Terre and present on massifs in the north-west as far north as Dôme de Tiébaghi. It appears to be restricted to ultramafic areas. Recorded up to 1,100 m asl. The extent of occurrence is estimated at 10,915 km2 and the area of occupancy at 252 km2.
Population
Bauer and Sadlier (1993) report that this species is common. There are no quantitative data on population size or trends. It is presumed to have suffered a past reduction in population size and extent through widespread simplification of maquis as a result of wildfires, and intensive but localized habitat loss associated with mining. The species is still relatively common at many localities, although the current and projected expansion of nickel mining will result in a further reduction of the area of occupied habitat throughout its range.
Habitat
Rhacodactylus auriculatus is found on the southern ultramafic block of New Caledonia and northward along the west coast and central-east coast ultramafic massifs. It inhabits humid forests, montane forests, and open and closed maquis (Bauer and Sadlier 2000). All Rhacodactylus species are excluded from agricultural and urban environments. This species is essentially nocturnal, but is sometimes active by day; primarily arboreal. It sometimes stays in the open on branches by day but usually shelters beneath dense vegetation on the ground or in tree cavities. It forages at night on the stems of shrubs and small trees (occasionally to 15 m above ground) or less commonly on the ground.
Threats
The close association of Rhacodactylus auriculatus to ultramafic substrates means that its habitat is vulnerable to the expanding nickel mining industry. This is a particular issue on the isolated massifs in the north-west of Grande Terre where almost every population is affected, and for large areas of the Grand Sud. The maquis habitat of R. auriculatus is also at risk to wildfires and, in the south of Grande Terre, to afforestation. Other threats include habitat degradation by introduced ungulates (deer and pigs) and predation by introduced mammals (rodents, feral cats and pigs). There is also a potential impact from the introduced ant, Wasmannia auropunctata, at low-elevation sites (Jourdan et al. 2000, 2001). Although the past illegal trade in this species has now largely abated due to the ease with which it can be bred in captivity, readily accessible populations are still at risk.
Conservation
Protected in Province Nord under Code de l'environnement de la Province Nord (Délibération No. 306-2008/APN, 24 October 2008) and in Province Sud under Code de l'environnement de la Province Sud (Délibération No. 25-2009/APS, 20 March 2009). Not listed on CITES. Present in Parc Provincial de la Rivière Bleue and many reserves in Province Sud, including Pic du grand Kaori, Mont Do, Montagne des sources, Cap N'dua, Nodela, Barrage de Yaté and Chutes de la Madeleine (but not present in any reserves in Province Nord). No conservation management is currently being undertaken.
Bibliography
Endemia.nc 2016. Faune et Flore de Nouvelle-Calédonie.
Jourdan, H., Sadlier, R.A. and Bauer, A.M. 2000. Premières observations sur les conséquences de l’invasion de Wasmannia auropunctata 1863 (Roger) sur les prédateurs supérieurs dans les écosystèmes Néo-calédoniens. Actes des collectes insectes sociaux(13) , p.121-126.
Bauer, A.M. and Sadlier, R.A. 1993. Systematics, biogeography and conservation of the lizards of New Caledonia. Biodiversity Letters(1) , p.107-122.
Jourdan, H., Sadlier, R.A. and Bauer, A.M. 2001. Little Fire Ant Invasion (Wasmannia auropunctata) as a threat to New Caledonian lizards: Evidences from a sclerophyll forest (Hymenoptera: Formicidae). Sociobiology(38) , p.283-301.
Bauer, A.M. and Sadlier, R.A. 2000. The Herpetofauna of New Caledonia.
IUCN 2021. The IUCN Red List of Threatened Species. Version 2021-2.
Uetz, P. (ed.) 2017. The Reptile Database.
Bauer, A.M. and Sadlier, R.A. 2001. New data on the distribution, status, and biology of the New Caledonian giant geckos (Squamata: Diplodactylidae: Rhacodactylus spp.). Amphibian and Reptile Conservation(2) , p.24-29.
Experts
Assessor(s): Sadlier, R., Bauer, A., Jourdan, H., Astrongatt, S., Deuss, M., Duval, T., Bourguet, E., McCoy, S., Bouteiller, A., Lagrange, A.
Reviewer(s): Cox, N.
Contributor(s): Whitaker, A.
Facilitator(s): Warimavute, G., Lietar, J., Tanguy, V.