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Montana Field Guide

Montana Field Guides

Pygmy Slug - Kootenaia burkei

Species of Concern
Native Species

Global Rank: G3
State Rank: S1S2

Agency Status

External Links

General Description
A small slug, extended adults usually < 15 mm. Dorsal base color is light gray or tan, with pale blue flecking to varying density. Mantle is oval with irregular dark gray to brown spots, the head extending a short distance beyond the anterior margin. The tail is rounded dorsally, lacks a middorsal keel, but sports a series of shallow, parallel longitudinal and oblique grooves that appear as darker lines; lacking a line of abscission, present in the taildroppers (Prophysaon). The sole is undivided (not tripartite), mucous clear. The pneumostome is slightly posterior to the midline of the mantle on the right side (Leonard et al. 2003, Hendricks 2012, Burke 2013). Internal anatomy is described by Leonard et al. (2003).

Diagnostic Characteristics
Distinguished by a combination of extremely small size, unkeeled tail, sole of foot undivided (not tripartite), gray or tan color with blue flecking, dark spots on mantle, a series of dark gray or brown parallel and longitudinal grooves on the tail, and the absence of a line a abscission.

Species Range
Montana Range


Range Comments
Southeastern British Columbia, northern Idaho and adjacent northwestern Montana west of the Continental Divide (Burke 2013). In Montana, 25 records in three counties: Lincoln (11), Mineral (4), Sanders (10). Elevation range is 668 to 1508 m (2190 to 4948 ft). May be locally abundant; 26 individuals were found at one Lincoln County site in early October (Hendricks 2012). Described as a new genus and species in 2003 based on animals collected at five northern Idaho sites during 2001-2003, first reported in Montana in 2005.

Observations in Montana Natural Heritage Program Database
Number of Observations: 28

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density



(Observations spanning multiple months or years are excluded from time charts)

Predicted Distribution in Montana
Predicted distribution model for Pygmy Slug (Kootenaia burkei). Records were spatially unique and had a locational uncertainty of ≤ 400 meters.  Hotter colors indicate areas that are predicted to have more suitable habitat for the species.  Black dots are positive data used to build the model.  Gray dots are locations where a survey capable of detecting the species has been performed.  Landownership, a shaded relief map, and county lines are included for reference.  Details of the modeling effort, a description of the environmental layers used, and a more thorough interpretation of model outputs can be found in the report Land Mollusk Surveys and Predicted Distribution Models on USFS Northern Region Lands: 2007.

Predicted Distribution Map

More model output for this species
Mostly mesic mixed conifer forest and riparian woodlands, but typically moister than for some other slug species. Canopy species often include western redcedar, western hemlock, grand fir, Engelmann spruce, Douglas-fir, black cottonwood, paper birch, sometimes subalpine fir, western white pine, western larch, ponderosa pine, and lodgepole pine; secondary canopy includes alder, dogwood and western yew. Usually found relatively near perennial streams and seeps under woody debris, rocks, on moss mats, within leaf litter, sometimes within rotten logs (Hendricks 2012).

Reproductive Characteristics
A captive individual laid eggs in mid-July that were near to hatching by mid September (Leonard et al. 2003).

  • Literature Cited AboveLegend:   View Online Publication
    • Burke, T. E. 2013. Land snails and slugs of the Pacific Northwest. Corvallis, OR: Oregon State University Press. 344 p.
    • Hendricks, P. 2012. A Guide to the Land Snails and Slugs of Montana. A report to the U.S. Forest Service - Region 1. Montana Natural Heritage Program, Helena, MT. vii + 187 pp. plus appendices.
    • Leonard, W.P., L. Chichester, J. Baugh, and T. Wilke. 2003. Kootenaia burkei, a new genus and species of slug from northern Idaho, United States (Gastropoda: Pulmonata: Arionidae). Zootaxa, 355: 1-16.
  • Additional ReferencesLegend:   View Online Publication
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    • Grimm, F.W., R.G. Forsyth, F.W. Schueler, and A. Karstad. 2009. Identifying land snails and slugs in Canada: introduced species and native genera. Canadian Food Inspection Agency, Ottawa, ON. 168 pp.
    • Hendricks, P., B.A. Maxell, and S. Lenard. 2006. Land mollusk surveys on USFS Northern Region lands. A report to the USDA Forest Service, Northern Region. Montana Natural Heritage Program, Helena, Montana. 11 pp. plus appendices.
    • Hendricks, P., B.A. Maxell, S. Lenard, and C. Currier. 2007. Land mollusk surveys on USFS Northern Region lands: 2006. A report to the USDA Forest Service, Northern Region. Montana Natural Heritage Program, Helena, Montana. 11 pp. plus appendices.
    • Hendricks, P., B.A. Maxell, S. Lenard, and C. Currier. 2008. Surveys and predicted distribution models for land mollusks on USFS Northern Region Lands: 2007. Report to the USDA Forest Service, Northern Region. Helena, MT: Montana Natural Heritage Program. 12 pp. + appendices.
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Citation for data on this website:
Pygmy Slug — Kootenaia burkei.  Montana Field Guide.  .  Retrieved on , from