Assessment Rationale:

This species was previously listed as Vulnerable (VU) D2 (version 2.3;  IUCN 1996), the latest evaluation suggests it could meet the criteria for Endangered  (EN) B1ab(iii) or Vulnerable (VU) D2 (version 3.1) depending on the severity of threats to these locations.  All recent records are only from three locations; the populations on Pico Branco and Ilhau de Cima are the safest, as there is no possibility of building development.  The third location on the mainland is most susceptible, from habitat loss from coastal erosion or habitat degradation due to invasive species (plants), fire or tipping or loss of populations due to introduced rodents. Given the maintained presence in low density at the three locations, the species should be maintained as Vulnerable (VU) D2.

Geographic Range:

This species is endemic to Madeiran islands where it is only known from Porto Santo, around Pico Branco, the southeast end of the island and the Ilhau de Cima (Seddon 2008) with similar distribution since 1878 (Wollaston 1878). Recent records (Field records 1984-1998) confirm the species is still living in all these locations.

Population:

Populations have been small since 1880's, although there is a possible decline of the mainland populations.

Habitat and Ecology

Caseolus calculus lives at the base of grasses and herbs and on rocky slopes.

Major Threat(s):

The population on the mainland coastal area is most susceptible, from habitat loss from coastal erosion or habitat degradation due to invasive species (plants), fire or tipping or loss of populations due to introduced rodents.

Conservation Actions

This species is listed on the EU Habitats and Species Directive Annex II and the Council of Europe Bern Convention Appendix 2. Recommended conservation actions include management of the protected areas for maintenance of this species and monitoring of the protected areas to ensure no loss of further habitat and subpopulations.