Listed as Critically Endangered as it is only known from one location, two islets ashore of Isle of Ile des Pins, with an extent of occurrence and area of occupancy estimated well below 4 km². There is a continuing decline in the extent and quality of habitat and number of mature individuals due to a variety of threats. In addition, the number of mature individuals known in each subpopulation is estimated well below 50 individuals with a total number of individuals estimated to be below 100.

Geographical area

Phoboscincus bocourti is endemic to Province Sud, New Caledonia. It is known to exist only on two islets ashore of Ile des Pins, New Caledonia (Ineich 2009). Its extent of occurrence (EOO) and area of occupancy (AOO) are estimated well below 4 km² (the islet surfaces are around 20 and 70 ha).

While it is speculated that the species may also occur on other islets of the Ile des Pins, on Ile des Pins itself and even on Grande Terre, there are no data at present to support this (Ineich 2006).

Population

There is no precise information on population size and trends for Phoboscincus bocourti. Until recently, it was presumed extinct, as no observations had been made since the holotype was collected (Bauer and Sadlier 2000). However, in December 2003 and November 2005, Ivan Ineich from Muséum national d'Histoire Naturelle, Paris recorded two individuals on a small islet off Ile des Pins, New Caledonia (Ineich 2006). Recent surveys conducted by IRD (Jourdan et al. 2014) recorded a few individuals on two islets (two individuals on one islet, 11 on the second islet), see also Caut et al. (2013).

The data available suggest that population density is low (or the species is very elusive). Given the very small size of the island on which it occurs, it is presumed that this is a relict population and that the species has been extirpated from Ile des Pins, and perhaps also Grande Terre, by a combination of habitat loss and predation by introduced mammals.

Habitat

The Ile des Pins is dominated by coastal humid forest. Very little is known of the species' ecology. It is presumed to be diurnal and terrestrial, but there is some evidence of arboreal behaviour (one found 1 m above ground on a horizontal branch, another climbed quickly up a vertical trunk when released). It occupies low coastal forest. It is presumed to bask, as one was observed motionless in a patch of sunlight.

Threats

Phoboscincus bocourti faces a number of potentially serious threats, which are exacerbated by the fact that it is a small population and confined to two very small, low and easily-accessible island, and has a very large body size (up to 284 mm SVL). Foremost amongst these threats is habitat loss and degradation. This could happen from an accidental fire that destroys a substantial area of the island's forest, from illegal timber cutting and from touristic activities. The status of invasive ants on the island is unknown but given their impact on lizards elsewhere in New Caledonia it is predicted they also would have a detrimental effect.

The islets where this species is present are islets where the black rat (Rattus rattus) is not yet introduced but tourism development with big cruise boats on Ile des Pins may incur more transit between the main island and the islet, hence fostering the risk of new introductions. The black rat is presumably exerting a predation pressure (Thibault 2017) on the skinks (large lizard species are markedly more vulnerable to rodents than small ones).

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. Not present in any reserve. No specific conservation management is currently being undertaken.

This species urgently needs a management plan.  A higher level of formal protection of the island and active management for conservation is a high priority for this species. A regulation/eradication plan for rats should be implemented immediately in Isle of Pines. As this species is present on islets where the Black Rat (Rattus rattus) is not yet introduced, urgent biosecurity preventive measures are needed. Monitoring is also needed to detect whether this species is currently declining. 

Bibliography

Morat, P.; Jaffré, T.; Tronchet, F.; Munzinger, J.; Pillon, Y.; Veillon, J.-M. and Chalopin, M. 2012. Le référentiel taxonomique Florical et les caractéristiques de la flore vasculaire indigène de la Nouvelle-Calédonie [The taxonomic database « FLORICAL » and characteristics of the indigenous flora of New Caledonia]. Adansonia sér 3(34) , p.177-219.

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

Hallé N.; Aubréville A.; Leroy J. F.; 1977. Flore de la Nouvelle-Calédonie et dépendances. Volume 08 : Orchidaceae.

Experts

Assessor(s): Laudereau, C., Butin, J., Antheaume, C., Cazé, H., Cazé, H., Fleurot, D., Garnier, D., Gâteblé, G., Maura, J.

Reviewer(s): Tanguy, V.

Facilitator(s): Tanguy, V., Maura, J.