Listed as Vulnerable because it has a restricted distribution, it occurs in less than 10 locations, and there is continuing decline in its extent of occurrence, area of occupancy, and extent and quality of its habitat. Genetic data (R. Sadlier, pers. comm. 2010) indicates that this species has a very high level of population sub-structuring. This translates into numerous isolated populations in humid forest fragments that are subject to an array of threats that could reduce its habitat or lead to population crashes with no perceived chance of re-colonization once extinct. Further research is recommended to determine if this species is experiencing population declines in response to intensifying threats, thereby warranting listing in a more threatened category.

Geographical area

Nannoscincus gracilis is endemic to New Caledonia. It occurs in widely scattered locations throughout the island from Mount Mandjélia in the north to Forêt de la Thy and Nouméa in the south (Bauer and Sadlier 2000). Most localities are in the central part of the island between Poindimié and Mont Do. The upper elevation limit of this species is 1,000 m asl. The extent of occurrence is estimated at 6,703 km² and the area of occupancy at 148 km².

Population

There are no quantitative data on population size and trends for Nannoscincus gracilis. It is assumed to have undergone substantial reduction in area of occupancy from the widespread loss of low to mid-elevation closed forests through clearance for agriculture and logging, and of mid- to high elevation forests for mining. The impact of wildfires from adjacent savanna and maquis will also have reduced the extent of forests through peripheral damage. It is considered locally common at some locations (Bauer and Sadlier 2000).

Habitat

It is known to inhabit closed humid forest and montane forest, and from sclerophyll forest in the Noumea region. This species is cryptozoic, semi-fossorial and terrestrial. It shelters beneath logs, stones and litter, and in cracks in the soil and forages through leaf litter. It is highly desiccation-prone. It is oviparous with two to three eggs per clutch, and the females are gravid during the rainy season from December to January (Bauer and Sadlier 2000).

Threats

Habitat loss and degradation is the primary threat to Nannoscincus gracilis. Further clearance for agriculture and afforestation will jeopardise the already highly fragmented low to mid-elevation forests of the central region, and the nickel mining industry threatens populations in montane forests on ultramafic substrata. The periphery of all closed forests is at risk from wildfires in adjacent savanna and maquis. All forests are also at risk to degradation by introduced ungulates (deer and pigs), leading to lower humidity, and from pigs disturbing the litter layer and cover. There are high infestations of the introduced ant Wasmannia auropunctata at many of the low to mid-elevation sites where N. gracilis occurs and these are expected to be a serious issue (Jourdan et al. 2000, 2001). Predation by rodents (Thibault 2017) and cats (Palmas 2017) may be a 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.

The distribution of this species occurs in protected areas, including Réserve de Nature Sauvage du Massif de l’Aoupinié and Mont Do, offering small safeguards against habitat loss and degradation. However, these areas need to be managed to provide effective conservation. No specific conservation management is currently being undertaken for this species. Research and monitoring of the population, habitat and threat status should be carried out.

Bibliography

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.

Endemia.nc 2016. Faune et Flore de Nouvelle-Calédonie.

IUCN 2021. The IUCN Red List of Threatened Species. Version 2021-2.

Bauer, A.M. and Sadlier, R.A. 2000. The Herpetofauna of New Caledonia.

Bauer, A.M. and Sadlier, R.A. 1993. Systematics, biogeography and conservation of the lizards of New Caledonia. Biodiversity Letters(1) , p.107-122.

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.

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.

Uetz, P. (ed.) 2017. The Reptile Database.

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): Lietar, J., Tanguy, V., Warimavute, G.