Taxonomy
Common name :
Le Gecko rayé des îles
Islands Striped Gecko Red List Status -
Endangered (EN) , assessed in 11/12/2017Protected species -
in Southern Province , in Northern ProvinceDescription
Description:
A small relatively stout species of gecko growing to a body length of 43mm, with a short tail 118% that of the body. It has moderately broad toes. The colour pattern on the body is highly variable, ranging typically mid brown above with a broad darker brown median region 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 only from the Iles Beleps (Ile Art & Ile Pott) and Ile Yandé NNW of Poum.
Distribution within Province Nord: see above.
Habitat:
It has been recorded from both maquis shrubland and closed forest habitats, and naiouli savannah – but was most common in closed forest.
Threats:
-
potentially high level of threat to maquis shrubland and closed forest habitat on the Ile Beleps from frequent firing of adjacent land under cultivation.
-
potentially high level of threat to closed forest with high infestation levels of introduced fire ants (Wasmannia auropunctata) causing significant declines in abundance.
-
moderate to high level of threat from predation by introduced rats and cats.
Conservation Status: Endangered
Dierogekko insularis has a restricted distribution (<100km2) spread over three locations, each a separate island, and on this criteria alone could be categorised as Vulnerable. At all sites it is threatened by mammalian predators, and on Ile Art to habitat damage and loss of habitat through wildfires The species has been identified as highly threatened (Bauer et al., 2006) and to meet the criteria to be categorised as Endangered.
Dierrogekko insularis is listed as Endangered because it is known from three locations with an extent of occurrence estimated at 43 km2 and the area of occupancy at 12 km2 and a continuing decline in its area of occupancy, extent and quality of its habitat and in the number of mature individuals due to a variety of threats.
Geographical area
This species is endemic to the Province Nord of New Caledonia. It is present in Iles Belep and Ile Yandé, northwest of Grande Terre. There are three known subpopulations (Ile Art, Ile Pott, and Ile Yandé). It occurs at elevations up to 280 m. The extent of occurrence is estimated at 43 km2 and the area of occupancy at 12 km2.
Population
Dierogekko insularis is still locally abundant at some sites where good habitat remains, but there is no information on present population trends. This species is presumed to have suffered a significant reduction in population size and extent due to habitat loss and degradation resulting from wildfires, clearance for agriculture and grazing, and past mining activities.
Habitat
Dierogekko insularis inhabits low, closed-forest remnants on rocky cuirasse surfaces (Ile Art and Ile Yandé), and rocky maquis shrublands (Ile Pott, Ile Art and Ile Yandé). It is nocturnal and arboreal, sheltering beneath stones by day, and climbing into the vegetation at night.
Threats
The populations on the Iles Belep are under constant threat from wildfires that encroach on the remaining areas of habitat. There is also localized pressure on habitat from clearance for subsistence gardening and timber harvest. Habitat degradation is also occurring on Ile Yandé from introduced ungulates (goats and pigs) but fortuitously there are no wild ungulates on the Iles Belep. Predation by rodents (Thibault 2017) and feral cats (Palmas 2017) is an issue at all locations where Dierogekko insularis occurs. The occurrence of Wasmannia auropunctata in forest habitats on these islands is also expected to have a severe and potentially unsustainable impact on the geckos, as these ants are known to decimate lizard populations and lead to localized extinctions (Jourdan et al. 2000, 2001). All three islands where the species occurs have been subjected to nickel exploration and localized mining in the past, and the increasing pressure on remaining ore reserves means the habitat of this species is at high risk, particularly on the cuirasse plateaux on Ile Art.
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). This species does not occur in any protected area. Research and monitoring of the population status, habitat and threats for this species should be carried out.
Bibliography
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., 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.
IUCN 2021. The IUCN Red List of Threatened Species. Version 2021-2.
Uetz, P. (ed.) 2017. The Reptile Database.
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.
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.
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., Lietar, J., Tanguy, V.