Assessment Rationale:

The last population surveys in 1986-1999 shows that the species population at the single site continues to be stable. In 2000 the species assessment was changed from Vulnerable to CR based on the increased traffic of tourism, the potential tourism developments in the eastern bays of the island (P. Craze pers. comm. 2000) and the lack of protection for the mainland of Porto Santo. There is a need to resurveys these populations to confirm that developments over the last 10 years have not impacted the species. Porto Santo now has designated protected areas, which should lead to a re-appraisal of the relative threat to the species, once the surveys have been completed, however, the assessment is left at Critically Endangered (CR) B2ab(iii) until this information is available.

Geographic Range:

Caseolus subcalliferus is endemic to Madeira, where it is only known from Porto Santo, on the eastern peninsular of Pico Branco (Seddon 2008). Here is it recorded from three closely adjacent sites in one location (Cameron et al. 1996, Seddon 2008).

Population:

There are no recent data on population trends, but it has always been a rare species, based on limited records from the literature (Wollaston 1877, M. Seddon, pers. comm. 2009).

Habitat and Ecology

This terrestrial species was described by Wollaston (1878) as living on upper parts of various plants including Juncus maritimus. Recent surveys have only found the species in areas of conifer plantation, where it was aestivating at up to 2 m up on the branches.

Major Threat(s):

These populations are most susceptible to habitat loss from land-use management (building, road or path construction) or fire. Habitat degradation due to invasive species (plants) or loss of subpopulations due to introduced rodents are secondary threats.

Conservation Actions

This species is listed on the EU Habitats and Species Directive Annex II and the Council of Europe Bern Convention Appendix 2 under the name Caseolus sphaerula. Habitat management plans to maintain the status of the habitats, reduce likelihood of fire and impact of recreational use on habitats in the area.