Taxonomy
Common name :
Le Gécko rayé des plaines
Red List Status -
Endangered (EN) , assessed in 11/12/2017Protected species -
in Southern Province , in Northern Province
Description
Description:
A small relatively stout species of gecko growing to a body length of 45 with a short tail 118% that of the body. It has moderately broad toes. The colour pattern on the body is highly variable, ranging markedly two-toned with a broad pale yellowish-brown dark median region above and brown at the sides, to a more poorly defined pattern where the body colour is almost uniformly light brown with a dorsolateral series of pale spots defining a marginally paler median region above.
Natural distribution:
Known from Riviére Nehoué and Dome de Tiébaghi in the northwest near Koumac.
Distribution within Province Nord: see above.
Habitat:
Low elevation vallicole forest along Riviére Nehoué; closed forest and maquis shrubland at Dome de Tiébaghi.
Threats:
-
potentially high level of threat to that part of the population inhabiting closed forest habitat with high infestation levels of introduced fire ants (Wasmannia auropunctata) causing significant declines in abundance.
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potentially high level of threat to remnant closed forest habitat on Dome de Tiébaghi through activities associated with mining leading to a decline in area, extent and quality habitat.
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moderate to high level of threat to remnant closed forest habitat on Dome de Tiébaghi from fire from adjacent maquis shrubland.
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localised but potentially intensive decline in area, extent and quality of humid forest habitat at Riviére Nehoué from exotic pests such as pigs, deer and cattle (high levels of disturbance of areas of the forest floor and of shelter sites).
Conservation Status: Endangered.
Dierogekko Nehouéensis has an restricted distribution (<100km2) and is known from only two adjacent areas only 2-5km apart, on this criteria alone could be categorised as Vulnerable. At both sites it is threatened by mammalian predators, and deer, pigs, and cattle are seriously impacting the forest at Riviére Nehoué and the closed forest on Dome de Tiébaghi. Closed forest habitat on Dome de Tiébaghi may also be at risk from future mining activities, although some gully forest has been set aside as botanical reserves. The species has been identified as highly threatened (Bauer et al., 2006) and to meet the criteria to be categorised as Endangered.
*Species occurring in localised areas of maquis shrubland are highly susceptible to catastrophic impact wildfires, and require pro-active conservation management to deal with this potential threat.
This species is listed as Endangered. Although it has a restricted distribution, it occurs in two locations with different types of habitats and threats. There is a continuing decline in its extent of occurrence, area of occupancy, the extent and quality of its habitat and the number of mature individuals, mainly caused by the mining activities and introduced species.
Geographical area
Dierogekko nehoueensis is endemic to Province Nord, New Caledonia. It is known only from the Dôme de Tiébaghi massif and adjacent lowlands, northern Grande Terre. It occurs at elevations up to 580 m. The extent of occurrence and the area of occupancy are estimated to be 32 km2.
Population
There are no quantitative data on population size or trends for Dierogekko nehoueensis, but it is still locally common at some sites with good habitat. However, the current expansion of the nickel mine on Dôme de Tiébaghi is reducing the area of occupied habitat and populations are noticeably declining in areas affected by pollution (dust) from the mine. This species is presumed to have suffered a substantial reduction in population size and extent with habitat loss from forest clearance for agriculture at low elevations and past mining activities (mainly at higher elevations).
Habitat
At Rivière Nehoué, Dierogekko nehoueensis occupies gallery forest on the floodplain; on Dôme de Tiébaghi it is present in closed-forest and in maquis shrubland. This species is nocturnal and arboreal, sheltering beneath stones and logs by day and climbing into the vegetation at night.
Threats
The major threat to Dierogekko nehoueensis is the current expansion of the nickel mine on Dôme de Tiébaghi as this will reduce the extent of habitat. Wildfires are a recurrent threat on Dôme de Tiébaghi, particularly in maquis shrublands. There is widespread habitat degradation throughout the range of these geckos from introduced ungulates such as deer and pigs (Jourdan 2014), plus cattle at Rivière Nehoué. The invasive ant, Wasmannia auropunctata, is abundant at Rivière Nehoué and in some closed forest areas on the massif. This ant species is expected to have a severe and potentially unsustainable impact on the geckos (Jourdan et al. 2000, 2001). Rodents and feral cats are numerous throughout the area and are expected to exert a predation pressure (Palmas 2017, Thibault 2017). Illegal collections and trafficking at accessible location are also estimated to have significant effects.
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). A small part of the habitat of Dierogekko nehoueensis at Rivière Nehoué is administered as a recreation reserve but it receives high human use. Two areas on the upper part of Dôme de Tiébaghi are unofficially set aside as botanical reserves, but to date this species has not been recorded within them. No conservation management is currently being undertaken.
Bibliography
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.
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.
Uetz, P. (ed.) 2017. The Reptile Database.
IUCN 2021. The IUCN Red List of Threatened Species. Version 2021-2.
Palmas, P., Jourdan, H., Rigault, F., Debar, L., De Meringo, H., Bourguet, E., Mathivet, M., Lee, M., Adjouhgniope, R., Papillon, Y. and Bonnaud, E. 2017. Feral cats threaten the outstanding endemic fauna of the New Caledonia biodiversity hotspot. Biological Conservation(214) , p.250-259.
Jourdan, H., Brescia, F. and Vidal, E. 2014. Programme R_Mines.Impact des espèces invasives sur les communautés de reptiles des massifs miniers.
Bauer, A.M., Jackman, T., Sadlier, R.A., Whitaker, A.H. 2006. A revision of the Bavayia validiclavis group (Squamata: Gekkota: Diplodactylidae), a clade of New Caledonian geckos exhibiting microendemism. Proceedings of the California Academy of Sciences(57) , p.503–547.
Thibault, M., Brescia, F., Vidal, E. and Jourdan, H. 2017. Invasive rodents, an overlooked threat for skinks in a tropical island hotspot of biodiversity. New Zealand Ecological Society(41) , p.74-83.
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., Tanguy, V., Lietar, J.