Geomalacus (Geomalacus) maculosus | Kerry Slug



Conservation status

Future Prospects
Overall Assessment of Conservation Status
Overall Trend in Conservation Status
Source: NPWS 2013.

IUCN Conservation Status

Ireland (1)Least Concern
Europe (2)*Not evaluated
Global (3)*Least Concern

* This species is only recorded in the wild from Spain, Portugal and Ireland so the global assessmnet may be interpreted as the European assessment.

**This assessment is acknowledged to be in need of updating.

Sources (1):Byrne, A. et al 2009; (2) The IUCN Red List of Threatened Species. Version 2014.3. (3): Mollusc Specialist Group 1996.

Legal status

Protected by the following legal instruments:

  • Habitats Directive [92/42/EEC] Annex I, Annex IV
  • Convention on the Conservation of European Wildlife and Natural Habitats (Bern Convention) Appendix II
  • Wildlife Act, 1976 as amended
  • Wildlife (Amendment) Act, 2000

Native status


Species Biology


  • A terrestrial slug between 6cms and 9 cms in length. It occurs in two colour varietys

            - brown with cream or off-white flecks

            -black / grey with white or off white-flecks.

  • Juveniles may also have lengthwise striping that fades with age.
  • Both colour varieties can occur in the same populations but the brown ground colour variety is more frequent in woodlands, the black / grey ground colour in more open habitats.
  • The Kerry Slug displays a not very common response to disturbance in that it will detach from the substrate and roll into a ball.

Sources: Reich, al, 2012; Mc Donnell, R.J. and Gormally, M.J., 2011.


In Ireland the Kerry Slug (Geomalacus maculosus) is very much associated with Devonian Old Red Sandstone geology in south west Ireland. In that area the species occurs in woodland, open heath and blanket bog. A population has been recorded in rocks around a lake on limestone, although the lake is of relatively low pH and there is peat deposition. A population has recently (2010) been recorded in conifer plantation on granitein Co. Galway.

At least in open areas, the species appears to require the presence of rocks, possibly for shelter in hot and / or dry periods.

The presence of lichens for feeding and bryophytes for feeding but more likely shelter, also seems important.

Habitats include but are not necessarily limited to;

  • Dry siliceous heath (HH3)
  • Wet heath (HH3)
  • Montane heath (HH4)
  • Dry-humid acid grassland (GS3)
  • Upland blanket bog (PB2)
  • Lowland blanket bog (PB3)
  • Cut-over bog (PB4)
  • Oak-birch-holly woodland (WN1)
  • Wet pedunculate oak-ash woodland (WN4)
  • Highly modified non-native woodland (WD) but not Scattered trees and parkland WD5)
  • Recently felled woodland (WS6)
  • Exposed siliceous rock (ER1)
  • Siliceous scree and loose rock (ER3)

Sources: Reich, al 2012; NPWS 2013; Mc Donnell, R.J. and Gormally, M.J., 2011; Anon., 2013; Fossitt, J.A. 2001.


Eggs laid July - October and take 6 to 8 weeks to hatch. Sexually mature in second year. Life-span to 6 years or so.

Source; Mc Donnell, R.J. and Gormally, M.J.

Threats faced

Invasive non-native species*
Forestry clearance
Forest replanting
Artificial planting on open ground (non-native trees)
Artificial planting on open ground (native trees)B01.01Low
Agricultural intensification

I* From notes in the Article 17 reporting for the 2007-2012 it would appear that the reference to 'invasive non-native species' is specifically to incursion of Rhododenron spp into semi-natural habitats, particularly woodlands, used by the Kerry Slug (Geomalacus maculosus).

Source: NPWS 2013.

A 2010 Threat Response Plan includes the following threat;

  • fragmentation of habitat and isolation of populations by major infrastructure such as roads.

Source: Anon. 2010.

Conservation actions

In the Article 17 Habitats Directive reporting for the period 2007-2012 Conservation Measures implemented or being implemented during the period were;

  • Continued legal protection of the species and its habitats inside and outside of Natura 2000 sites
  • Legal measures to adapt forest management
  • Recurrent measures to restore / improve forest habitats.

Source: NPWS 2013.

A 2010 Threat Response Plan for Geomalacus maculosus included 17  'Future Actions'. The Threat Response Plan was reviewable annually over a three year period. The Threat Response Plan is available via the National Parks and Wildlife website. A selection of 'Future Actions' is included below.

  • Encourage international scientific co-operation on research into genetic variability between and within Irish and Iberian populations of Geomalacus maculosus.
  • Encourage surveying and recording of Geomalacus maculosus.
  • Review forestry guidelines and schemes to ensure they are consistent with the conservation of Geomalacus maculosus and its habitats.
  • Endeavour to include the presence of Geomalacus maculosus in the definition of High Conservation Value Forest in Ireland.
  • Continue the eradication of Rhodendron ponticum and Prunus laurocerasus from Killarney National Park and Glengarriff Nature Reserve.
  • Ensure appropriate species protection policies for are inserted into all relevant land-use plans, such as County Development Plans, Functional Area Plans and Local Plans.
Source: Anon. 2013.


World distribution(GBIF)

The Kerry slug (Geomalacus maculosus) has a restricted distribution, limited to the south west of Ireland and the north west of Iberia (Spain and Portugal).

Accuracy of world distribution shown in the Global Biodiversity Information Facility (GBIF) map below will be constrained by, amongst other factors, data held but not shared by countries and organizations not participating in the GBIF.

Irish distribution

 Current known main populations are located in the south west (Cork and Kerry) with a recently (2010) discovered population in Co. Galway.

Temporal change

Records submitted to Data Centre in 2022

The following map is interactive. If you would prefer to view it full screen then click here.

How can you help

The National BiodiversityData Centre is trying to improve our knowledge on the distribution of the Kerry Slug in Ireland. Should you observe this species, please submit sightings to add to the database. Detailed observations will assist us gaining a betterinsight into where the Kerry Slug is most abundant in Ireland and we might also be able to detect regional variations. Please submit any sightings and photographs at:

All records submitted online can be viewed on Google Maps – once checked and validated these will be added to the database and made available for conservation and research.

Further information

For further information contact Dr. Liam Lysaght



Anon, (2010) Threat Response Plan, Kerry Slug, Geomalacus maculosus. Department of Environment, Heritage and Local Government.

Byrne, A., Moorkens, E.A., Anderson, R., Killeen, I.J. & Regan, E.C. (2009) Ireland Red List No. 2 – Non-Marine Molluscs. National Parks and Wildlife Service, Department of the Environment, Heritage and Local Government, Dublin, Ireland.

Fossitt, J.A. (2001). A Guide to Habitats in Ireland. The Heritage Council.

Mc Donnell, R.J. and Gormally, M.J. (2011). Distribution and population dynamics of the Kerry Slug, Geomalacus maculosus (Arionidae).Irish Wildlife Manuals, No. 54. National Parks and WildlifeService, Department of Arts,Heritage and the Gaeltacht, Dublin, Ireland.

Mollusc Specialist Group 1996. Geomalacus maculosus. The IUCN Red List of Threatened Species. Version 2014.2. <>. Downloaded on 18 September 2014.

NPWS (2013) The Status of EU Protected Habitats and Species in Ireland.  Species Assessments Volume 3. Version 1.0. Unpublished Report, National Parks & Wildlife Services. Department of Arts, Heritage and the Gaeltacht, Dublin, Ireland.

Reich, I., O’Meara, K., Mc Donnell, R.J. and Gormally, M.J. (2012) An assessment of the use of conifer plantations by the Kerry Slug (Geomalacus maculosus) with reference to the impact of forestry operations.Irish Wildlife Manuals, No. 64. National Parks and Wildlife Service, Department of Arts, Heritage and the Gaeltacht, Ireland.

The IUCN Red List of Threatened Species. Version 2014.3. <>. Downloaded on 06 January 2015.