Geomalacus maculosus 

Scope: Global
Language: English

Translate page into:

Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Mollusca Gastropoda Stylommatophora Arionidae

Scientific Name: Geomalacus maculosus Allman, 1843
Common Name(s):
English Kerry Slug
Taxonomic Source(s): Bank, R.A. 2013. Fauna Europaea: Mollusca: Gastropoda. Available at:

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2017
Date Assessed: 2016-06-22
Assessor(s): Rowson, B.
Reviewer(s): Duda, M. & Allen, D.J.
This species is widespread and not uncommon in either its Iberian or Irish (introduced) range. It has a large extent of occurrence (EOO) overall. There is some evidence of decline and threat from habitat loss and degradation in Spain, where the species is listed as Vulnerable (VU) (Castillejo and Iglesias 2011). The Iberian subpopulations may be considered especially important for conservation, given the evidence that the Irish population is genetically impoverished and where the origin is uncertain (Reich et al. 2015). Furthermore, a continued long-term decline in the number of subpopulations could make this species meet more stringent criteria in future. At present the species is assessed as Least Concern (LC), however habitat and population monitoring is recommended.
Previously published Red List assessments:

Geographic Range [top]

Range Description:This species is native to northwestern Spain and Portugal, where it is found in the Serra da Estrela (Portugal), Galicia and Cantabria (Spain) (Castillejo 1997, 1998, Bank 2007, Castillejo and Iglesias 2011). It is also widespread in western Ireland, where it is a protected species, now considered to be an ancient introduction (Reich et al. 2015). A 19th century record from Brittany, France is considered erroneous (Platts and Speight 1988, McDonnell and Gormally 2011). In Iberia the EOO is approximately 65,000 km2.
Countries occurrence:
Portugal (Portugal (mainland)); Spain (Spain (mainland))
Additional data:
Upper elevation limit (metres):300
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:In Spain this species is listed as Vulnerable (VU) under criterion B1ab(i,ii,iii) (Castillejo and Iglesias 2011). This refers to a continuing decline in the extent of occurrence (EOO), area of occupancy (AOO) and the quality of oak and chestnut habitats. These are assumed to correspond to reductions in the Spanish population, despite the species sometimes being one of the commonest slug species at a site. The overall population of the species is assumed to be somewhat stable, but at some risk of depletion in Iberia.

In Ireland, this species is not considered threatened, is said to have a strong viable population, and may be capable of expanding its range with global warming (Byrne et al. 2009). Fieldwork carried out in Ireland (McDonnell and Gormally 2011) found three hectads in which the species had not been recorded since before 1965, but also revealed six additional hectads from which the species had not previously been recorded. One of these was in a plantation far from the known range and is considered an introduction. The study showed that this species is often one of the most common slugs at a site, although its density is reduced by Rhododendron (Rhododendron ponticum) invasion, burning of peatlands, and conifer afforestation. The Irish population is therefore assumed to be stable or increasing.
Current Population Trend:Stable
Additional data:

Habitat and Ecology [top]

Habitat and Ecology:This is a lichenivorous species. In Iberia, it is a species of coastal and montane oak and chestnut woodland and groves (oak Quercus spp., Castanea sativa) and pine woodland (Pinus pinaster) as well as rocky or walled areas (Castillejo 1998, Castillejo and Iglesias 2011). In Ireland, it inhabits oak woodland, open peat bogs with rocky outcrops, and conifer plantations (McDonnell and Gormally 2011, Rowson et al. 2014).

Use and Trade [top]

Use and Trade: This species is not used or traded.

Threats [top]

Major Threat(s): There are no threats affecting the whole population of this species. However, in Spain it is threatened specifically by logging of chestnut and oak (Castillejo and Iglesias 2011). In Ireland it is possibly threatened by Rhododendron (Rhododendron ponticum) invasion, burning of peatlands, and conifer afforestation (McDonnell and Gormally 2011). In both cases deforestation and air pollution have also been considered potential threats.

Conservation Actions [top]

Conservation Actions: There is no single threat to the whole population of this species. In Spain it is listed as Vulnerable (VU) under criterion B1ab(i,ii,iii) (Castillejo and Iglesias 2011). Limiting the logging of chestnut and oak woodland is recommended. In Ireland it has been listed as Least Concern (LC).

Citation: Rowson, B. 2017. Geomalacus maculosus. The IUCN Red List of Threatened Species 2017: e.T9049A85983466. . Downloaded on 23 May 2018.
Disclaimer: To make use of this information, please check the <Terms of Use>.
Feedback: If you see any errors or have any questions or suggestions on what is shown on this page, please provide us with feedback so that we can correct or extend the information provided