IUCN SSC Mid-Atlantic Island Invertebrates Specialist Group

Species

BackDiscula testudinalis Pfeiffer, 1853

Discula testudinalis Pfeiffer, 1853

Madeiran Land Snail

  • Kingdom: Animalia
  • Phylum:
  • Class: Mollusca
  • Order: Gastropoda
  • Family: Hygromiidae
CR Critically Endangered
IUCN Red List Status:

Countries of Occurrence:
Portugal - Madeira

Archipelago(s):
Madeira

Assessor/s:
Seddon, M.B.

Reviewer/s:
Cameron, R., Groh, K., Cuttelod, A. & Neubert, E.

Contributor/s:

Facilitators / Compilers/s:


Assessment Rationale:

This species has been listed since 1980s, and still remains rare, as well as susceptible to predation from non-native species. The area of occupancy is under 10 km2, and hence meets the threshold for Critically Endangered, as the two closely located sites (Seddon 2008, map 174) are considered a single location given the threats of fire and predation from non-native species. There is concern for the survival of this species, as there are potential problems of changing land-use and evidence that a rodent is feeding on other species of Discula with similar shell size and form. This species is therefore assessed as Critically Endangered B1ab(iii)+2ab(iii).

Geographic Range:

This species is restricted to Porto Santo, on the north side of the main island. Waldén (1983) believed the species might be extinct but Seddon (pers. comm. 1992) noted it was still present in a small region of headland where originally found by Wollaston (1878), and the finding was reported in Wells and Chatfield (1992) where the species was noted to be present on dry stony ground on the headland of Pedragal in an area of 10 m2 only. Another site was located close by during Cameron and Cook's surveys and mapped by Seddon (2008).

Regions:
Portugal - Madeira
Extent of Occurrence (EOO):
(km2)
Area of Occupancy (AOO):
10 (km2)
Elevation Lower Limit:
(m)
Elevation Upper Limit:
(m)
Biogeographic Realms:
Palearctic
Presence:
Extant
Origin:
Endemic Madeira
Seasonality:
Resident

Population:

The species is very rare. It is usually found in specialist surveys targeted at the species.

Habitat and Ecology

This species is found in grassland areas on cliffs, where it's found under stones or in small scree areas.

Major Threat(s):

The main threats to this species are fire and predation from non-native species, in two closely sites on small headland, which is considered to be a single location.

Conservation Actions

This species is listed on the EU Habitats and Species Directive Annex II and the Council of Europe Bern Convention Appendix 2. At present the range does not lie in a designated SPA, and so protected area management is needed, as well as management of the introduced predators (rats) that are feeding on this species.