Mature exotic conifer stands have greater catches of the EU-protected Geomalacus maculosus than adjacent peatland or clear-felled stands—implications for forestry

  • Erin Johnston
  • Gesche Kindermann
  • Jack O’Callaghan
  • Daniel Burke
  • Cillian McLoughlin
  • Sinéad Horgan
  • Inga Reich
  • Rory Mc Donnell
  • Christopher D. Williams
  • Michael Gormally
Original Paper


Key message

Mature exotic Sitka spruce ( Picea sitchensis ; Bong. Carrière)-dominated stands, particularly trees of greater circumference, result in greater numbers of Geomalacus maculosus (Allman) captures than adjacent clear-felled stands and adjacent peatland with Before-After-Control-Impact-Paired analysis indicating lower catches of G. maculosus post-felling.


The discovery of EU-protected Geomalacus maculosus in commercial plantations requires an understanding of the implications of forestry practices for the species within the context of sustainable forest management.


  1. 1.

    Compare Geomalacus maculosus captures across mature exotic Sitka spruce-dominated stands, previously clear-felled stands and adjacent peatland habitats.

  2. 2.

    Assess the suitability, for forest managers, of population estimate models for G. maculosus.

  3. 3.

    Assess the implications of felling by comparing relative abundances of G. maculosus directly before and after clear-felling at a mature exotic Sitka spruce-dominated stand.



Geomalacus maculosus catches were compared at four sites across two to three mature (43–45 years old) conifer stands per site, one clear-felled stand per site, and one adjacent peatland per site using refuge traps and hand searching. Capture-mark-recapture studies were undertaken to estimate population sizes. A BACIP (Before-After-Control-Impact-Paired) analysis was undertaken in one forest stand at one forest site to determine impacts of a clear-felling event.


Mean catches of Geomalacus maculosus adults in the mature forest stands were over 10 and 11 times greater than mean catches on peatland and clear-fell stands, respectively. The Schnabel model for estimating population size was most suited for mature forest stands but could not be utilised for the other habitats. BACIP analysis showed a significant impact of clear-felling with a 95% reduction in mean G. maculosus catches after a clear-felling event where none of the individuals marked prior to felling were recaptured compared to 21% recapture rates at the control site. Greater tree circumference in mature conifer stands correlated with greater catches.


Guidelines are needed to ensure the protection of Geomalacus maculosus in commercial forestry. Interventions could include patch/tall stump retention at final felling and/or translocation of the protected species.


Conservation Capture-mark-recapture Population estimates Before-After-Control-Impact-Paired (BACIP) Slug 



We are grateful to Aidan O’Hanlon, Clément Teillet, Declan McGovern, Lorenzo Sardo, Mark Welch, Úna Ní Ruairc and Frank O’Grady for assistance with fieldwork. We would also like to thank Stacey Bradly, Eamon Drohan, Joan O’Connor, Ted Kelleher, Padraig McMahon and Ciaran Walsh (Coillte) for providing information on the sites and Coillte for permitting access to the sites. Thank you to Dr. Aileen O Sullivan (Coillte) and Dr. Orla Fahy (Forest Service) for their assistance. We acknowledge, with thanks, the Wildlife Licensing Unit (National Parks & Wildlife Service) for providing us with licence no. C069/2014 and the Department of Agriculture, Food and the Marine for funding this research under the FIRM/RSF/CoFoRD 2013 Research Call. Finally, we wish to thank the reviewers and editors for their insightful and helpful comments.


This project was funded by the Department of Agriculture, Food and the Marine under the FIRM/RSF/CoFoRD 2013 Research Call.


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Copyright information

© INRA and Springer-Verlag France SAS, part of Springer Nature 2017

Authors and Affiliations

  • Erin Johnston
    • 1
  • Gesche Kindermann
    • 1
  • Jack O’Callaghan
    • 1
  • Daniel Burke
    • 1
  • Cillian McLoughlin
    • 1
  • Sinéad Horgan
    • 1
  • Inga Reich
    • 2
  • Rory Mc Donnell
    • 2
  • Christopher D. Williams
    • 3
  • Michael Gormally
    • 1
  1. 1.Applied Ecology Unit, Centre for Environmental Science, School of Natural SciencesNational University of Ireland GalwayGalwayIreland
  2. 2.Department of Crop and Soil ScienceOregon State UniversityCorvallisUSA
  3. 3.School of Natural Sciences and PsychologyLiverpool John Moores UniversityLiverpoolUK

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