COSEWIC Assessment and Status Report on the Pygmy Slug Kootenaia burkei in Canada - 2016

Pygmy Slug
Photo: © Kristiina Ovaska., 2016

Special concern
2016


Document information

COSEWIC
Committee on the Status
of Endangered Wildlife
in Canada

COSEWIC logo

COSEPAC
Comité sur la situation
des espèces en péril
au Canada

COSEWIC status reports are working documents used in assigning the status of wildlife species suspected of being at risk. This report may be cited as follows:

COSEWIC. 2016. COSEWIC assessment and status report on the Pygmy Slug Kootenaia burkei in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. x + 53 pp.

(Species at Risk Public Registry website).

Production note:

COSEWIC would like to acknowledge Kristiina Ovaska and Lennart Sopuck for writing the status report on the Pygmy Slug in Canada. This report was prepared under contract with Environment Canada and was overseen by Joe Carney, Co-chair of the COSEWIC Molluscs Specialist Subcommittee.

For additional copies contact:

COSEWIC Secretariat
c/o Canadian Wildlife Service
Environment and Climate Change Canada
Ottawa, ON
K1A 0H3

Tel.: 819-938-4125
Fax: 819-938-3984
E-mail: COSEWIC E-mail
Website: COSEWIC

Également disponible en français sous le titre Ếvaluation et Rapport de situation du COSEPAC sur la Limace pygmée (Kootenaia burkei) au Canada.

Cover illustration/photo:

Pygmy Slug - photo credit Kristiina Ovaska.


COSEWIC assessment summary

Assessment summary - May 2016

Common name
Pygmy Slug
Scientific name
Kootenaia burkei
Status
Special concern
Reason for designation
In Canada, this small slug is confined to the moist forests of the northern Columbia basin of British Columbia. It is found in moist mixed-wood and coniferous forests and commonly associated with riparian habitats along small creeks. Key habitat requirements include high substrate moisture with abundant woody debris and leaf litter for shelter. Threats include: existing and new roads resulting in fragmentation, increased edge effects, and barriers to dispersal; predation and competition from invasive species; damage to riparian areas associated with livestock grazing; habitat loss and degradation associated with logging activities; and, projected consequences of climate change, including an increase in drought conditions and an increase in both the number and severity of wildfires.
Occurrence
British Columbia
Status history
Designated Special Concern in April 2016.

COSEWIC executive summary

Pygmy slug
Kootenaia burkei

Wildlife species description and significance

Pygmy Slug is the sole member of the newly described genus Kootenaia. As its common name implies, Pygmy Slug is very small with adults usually 9 - 14 mm long. The colour is from dark grey to tan with dense bluish flecking covering the mantle and tail; dark mottling is often present on the mantle. The tail is rounded (lacking a keel) with a series of parallel and oblique longitudinal grooves, which may resemble thin dark stripes. Pygmy Slug is a regional endemic to moist forests of the northern Columbia Basin, an area that contains many unique plants and animals.

Distribution

The global distribution of Pygmy Slug extends from southeastern British Columbia through the Idaho Panhandle to northwestern Montana. In Canada, Pygmy Slug occurs in the Selkirk and Purcell sub-ranges within the Columbia Mountains in southeastern British Columbia. The species is known from 44 sites in the province; the number of sites may continue to expand with increasing search effort. Approximately 36% of the species' distribution is in Canada.

Habitat

In British Columbia, the slugs occur mostly within the Interior Cedar-Hemlock biogeoclimatic zone, which is among the wettest areas in the interior of the province. The slugs have been found in moist mixed-wood and coniferous forests from low to mid-elevations (580 m - 1585 m), where they are commonly associated with riparian habitats along small tributary creeks. High substrate moisture and abundant shelter, such as provided by coarse woody debris or pockets of deep leaf litter, appear to be key habitat requirements. The slugs have been found from 40 - 50-year-old second growth to old growth (>200 years old) stands. Common trees at occupied sites included Western Redcedar and Black Cottonwood; the understorey often contained moisture-loving plants, such as Thimbleberry, Devil's Club, and Lady Fern.

Biology

The natural history of Pygmy Slug is poorly known. The slugs are hermaphroditic, but the exchange of sperm with other individuals rather than self-fertilization is probably the norm. The slugs lay small clutches of eggs, which are relatively large (10% or more of parent body length). The slugs are known to feed on lichens and fungi and probably also consume decaying organic matter in the duff layer. Most observations in British Columbia and the United States have taken place in autumn, when the slugs are active on the forest floor. Juveniles and an unknown proportion of adults probably overwinter. The generation time is approximately 1 year. The small size of the slugs may enable them to exploit small habitat patches provided that their requirements for moisture and shelter are met. Slugs in general are poor dispersers if not aided by humans or by wind or water; no such passive means of dispersal are known for Pygmy Slug, exacerbating the effects of habitat fragmentation on its distribution within the landscape.

Population size and trends

Population sizes and trends of Pygmy Slug are unknown. Survey efforts have focused on elucidating the distribution of Pygmy Slug rather than on obtaining abundance estimates. Records for the species from British Columbia are from 2007 - 2015, precluding information on population trends.

Threats and limiting factors

The Canadian distribution of Pygmy Slug most likely reflects post-glacial expansion from refugia farther south. Its present distribution is probably limited by a short growing season and/or long and cold winters to the north, and drier forest types to the east and west. Low dispersal ability and requirements for moist habitats limit the speed at which the slugs can colonize new habitats.

Pygmy Slug populations are threatened by extreme events associated with climate change, introduced invasive species, fire and fire suppression, logging, roads, and livestock farming and ranching. The greatest threats to the slugs across their Canadian range are deemed to be from droughts and flood events, the frequency and severity of which are predicted to continue to increase under climate change scenarios. Invasive, non-native species that threaten slug populations include introduced gastropods, which are inadvertently spread by humans and which prey on or compete with native species, and other invertebrate predators such as ground beetles, which can be aggressive predators of slugs. Frequency and severity of wildfires is projected to increase with climate change. Due to their low mobility, gastropods are both unable to escape fire events by moving away and are slow to recolonize burnt areas. Logging is prevalent throughout the Pygmy Slug's range and continues to modify and fragment habitats. The effects of logging on slugs may be mitigated to some degree by riparian buffers, which are required along larger water courses containing fish, or which logging companies may leave voluntarily along small, fishless streams where they are not required. Logging roads and other resource roads also continue to fragment habitats.

Protection, status, and ranks

Pygmy Slug has no official protection or status under the federal Species at Risk Act, B.C. Wildlife Act, or other legislation. Pygmy Slug is ranked by NatureServe as follows: Global status - G2 (imperilled); United States - N2 (imperilled); Canada - N1 (critically imperilled); Idaho: S2 (imperilled); Montana - S1S2 (critically imperilled to imperilled; BC:S1? (possibly critically imperilled). In British Columbia, the species is on the provincial red list of species at risk.

Across the Pygmy Slug's Canadian range, protected lands comprise approximately 20% of the land base and include several provincial parks, provincial Wildlife Habitat Areas established for other species, and other conservation lands. Pygmy Slug has not been recorded from any of the above areas with the exception of one site within a small conservation area. Most of the range and known sites are within provincial forestry lands.


Technical summary

Scientific name:
Kootenaia burkei
English name:
Pygmy Slug
French name:
Limace pygmée
Range of occurrence in Canada:
British Columbia

Demographic Information

Demographic Information
Summary itemsInformation
Generation time (usually average age of parents in the population; indicate if another method of estimating generation time indicated in the IUCN guidelines(2008) is being used)~1 yr
Is there an [observed, inferred, or projected] continuing decline in number of mature individuals?Unknown
Estimated percent of continuing decline in total number of mature individuals within [5 years or 2 generations]Unknown
[Observed, estimated, inferred, or suspected] percent [reduction or increase] in total number of mature individuals over the last [10 years, or 3 generations].Unknown
[Projected or suspected] percent [reduction or increase] in total number of mature individuals over the next [10 years, or 3 generations].Unknown
[Observed, estimated, inferred, or suspected] percent [reduction or increase] in total number of mature individuals over any [10 years, or 3 generations] period, over a time period including both the past and the future.Unknown
Are the causes of the decline clearly reversible and understood and ceased?NA
Are there extreme fluctuations in number of mature individuals?Probably not

Extent and Occupancy Information

Extent and Occupancy Information
Summary itemsInformation
Estimated extent of occurrence15,552 km2
Index of area of occupancy (IAO) (Always report 2x2 grid value).180 km2 (discrete; 45 2 x 2 km grid cells); 1160 km2 (continuous along water courses; 290 2 x 2 km grid cells)
Is the population severely fragmented?Unknown
Number of locations>20 based on number of occupied sub-watersheds and threat from climate change and severe weather or invasive species
Is there an [observed, inferred, or projected] continuing decline in extent of occurrence?Unknown
Is there an [observed, inferred, or projected] continuing decline in index of area of occupancy?Unknown
Is there an [observed, inferred, or projected] continuing decline in number of populations?Unknown
Is there an [observed, inferred, or projected] continuing decline in number of locations?
(Note: See Definitions and Abbreviations on COSEWIC website and IUCN (Feb 2014) for more information on this term.)
Unknown
Is there an [observed, inferred, or projected] continuing decline in [area, extent and/or quality] of habitat?Yes, observed, inferred, and projected decline habitat quality
Are there extreme fluctuations in number of populations?No
Are there extreme fluctuations in number of locations?No
Are there extreme fluctuations in extent of occurrence?No
Are there extreme fluctuations in index of area of occupancy?No

Number of Mature Individuals (in each population)

Number of Mature Individuals (in each population)
PopulationN Mature Individuals
TotalUnknown

Quantitative Analysis

Quantitative Analysis
Summary itemsInformation
Probability of extinction in the wild is at least [20% within 20 years or 5 generations, or 10% within 100 years].Not done

Threats (actual or imminent, to populations or habitats)

Threats (actual or imminent, to populations or habitats)
Summary itemsInformation

Was a threats calculator completed for this species? Yes

  1. Livestock farming & ranching (2.3)
  2. Roads & railroads (4.1)
  3. Logging and wood harvesting (5.3)
  4. Fire & fire suppression (7.1)
  5. Invasive non-native species (8.1)
  6. Climate change and severe weather: Droughts (11.2), Storms & flooding (11.4)

What additional limiting factors are relevant?

Low dispersal capabilities; dependence on moist micro-habitats

Rescue Effect (immigration from outside Canada)

Rescue Effect (Immigration from outside Canada)
Summary itemsInformation
Status of outside population(s)?G2 (Global), N2 (US), S2 (Idaho), SIS2 (Montana)
Is immigration known or possible?Not known but possible
Would immigrants be adapted to survive in Canada?Yes
Is there sufficient habitat for immigrants in Canada?Yes
Are conditions deteriorating in CanadaYes
Are conditions for the source population deterioratingYes
Is the Canadian population considered to be a sink?No
Is rescue from outside populations likely?Possible over long term in some areas near the border, but rate would be very low

Data Sensitive Species

Data Sensitive Species
Summary itemsInformation
Is this a data sensitive species?No

Status History

Status History
Summary itemsInformation
COSEWICNot previously assessed.

Status and Reasons for Designation:

Status and Reasons for Designation:
Summary itemsInformation
StatusSpecial Concern
Alpha-numeric codeNot applicable
Reasons for designationIn Canada this small slug is confined to the moist forests of the northern Columbia basin of British Columbia. It is found in moist mixed-wood and coniferous forests and commonly associated with riparian habitats along small creeks. Key habitat requirements include high substrate moisture with abundant woody debris and leaf litter for shelter. Threats include: existing and new roads resulting in fragmentation, increased edge effects, and barriers to dispersal; predation and competition from invasive species; damage to riparian areas associated with livestock grazing; habitat loss and degradation associated with logging activities; and projected consequences of climate change, including an increase in drought conditions and an increase in both the number and severity of wildfires.

Applicability of Criteria

Applicability of Criteria
Summary itemsInformation
Criterion A (Decline in Total Number of Mature IndividualsNot applicable as no estimates of population size or trends are available.
Criterion B (Small Distribution Range and Decline or FluctuationNot applicable. EOO (15,552 km2) meets the threshold for Threatened (< 20,000 km2) and IAO (180 km2) meets the threshold for Endangered (< 500 km2) and Threatened (< 2,000 km2), the population is not severely fragmented and the number of locations (>20) exceeds the thresholds, and there are no extreme fluctuations.
Criterion C (Small and Declining Number of Mature IndividualsNot applicable. No estimates of population size or trends are available.
Criterion D (Very Small or Restricted Population)Not applicable.
There are no estimates of population sizes, and D2 for Threatened does not apply as both the IAO and number of locations exceed the thresholds.
Criterion E (Quantitative Analysis)Not applicable. No quantitative analyses have been performed.

COSEWIC history

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal-Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. Species designated at meetings of the full committee are added to the list. On June 5, 2003, the Species at Risk Act (SARA) was proclaimed. SARA establishes COSEWIC as an advisory body ensuring that species will continue to be assessed under a rigorous and independent scientific process.

COSEWIC mandate

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assesses the national status of wild species, subspecies, varieties, or other designatable units that are considered to be at risk in Canada. Designations are made on native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fishes, arthropods, molluscs, vascular plants, mosses, and lichens.

COSEWIC membership

COSEWIC comprises members from each provincial and territorial government wildlife agency, four federal entities (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biodiversity Information Partnership, chaired by the Canadian Museum of Nature), three non-government science members and the co-chairs of the species specialist subcommittees and the Aboriginal Traditional Knowledge subcommittee. The Committee meets to consider status reports on candidate species.

Definitions (2015)

Wildlife Species
A species, subspecies, variety, or geographically or genetically distinct population of animal, plant or other organism, other than a bacterium or virus, that is wild by nature and is either native to Canada or has extended its range into Canada without human intervention and has been present in Canada for at least 50 years.
Extinct (X)
A wildlife species that no longer exists.
Extirpated (XT)
A wildlife species no longer existing in the wild in Canada, but occurring elsewhere.
Endangered (E)
A wildlife species facing imminent extirpation or extinction.
Threatened (T)
A wildlife species likely to become endangered if limiting factors are not reversed.
Special Concern (SC)
(Note: Formerly described as "Vulnerable" from 1990 to 1999, or "Rare" prior to 1990.)
A wildlife species that may become a threatened or an endangered species because of a combination of biological characteristics and identified threats.
Not at Risk (NAR)
(Note: Formerly described as "Not In Any Category", or "No Designation Required.")
A wildlife species that has been evaluated and found to be not at risk of extinction given the current circumstances.
Data Deficient (DD)
(Note: Formerly described as "Indeterminate" from 1994 to 1999 or "ISIBD" [insufficient scientific information on which to base a designation] prior to 1994. Definition of the [DD] category revised in 2006.)
A category that applies when the available information is insufficient (a) to resolve a species' eligibility for assessment or (b) to permit an assessment of the species' risk of extinction.

The Canadian Wildlife Service, Environment and Climate Change Canada, provides full administrative and financial support to the COSEWIC Secretariat.


Wildlife species description and significance

Name and classification

Pygmy Slug, Kootenaia burkei, was described from specimens from northern Idaho in 2003 (type locality: Little Bumblebee Creek, Panhandle National Forest; Leonard et al. 2003). The species is the sole representative of the genus, placed within the large cosmopolitan family Arionidae (Leonard et al. 2003). An alternative classification by Bouchet and Rocroi (2005) raises all arionid subfamilies to full family status. Neither of these classifications is satisfactory, because current genetic studies do not support the monophyly of the more inclusive Arionidae or its subfamilies that have been investigated (Backeljau pers. comm. 2011).

Of other North American arionid genera, Kootenaia is most closely related to Prophysaon, but genetic divergence and comparative anatomy clearly set the two apart (Leonard et al.. 2003). In addition to Prophysaon, Burke (2013) placed Kootenaia and two newly discovered monotypic genera, Carionarion and Securicauda (Leonard et al.. 2011), in Anadenidae (Anadeninae in other classifications), but without explanation.

The current classification is as follows:

Phylum Mollusca
Class Gastropoda
Subclass Pulmonata
Order Stylommatophora
Suborder Arionoidea
Family Arionidae
(Subfamily Anadeninae)
Genus Kootenaia
Species Kootenaia burkei

The genus is named after the Kootenay First Nation, who historically occupied the land that encompasses the species' range (Leonard et al. 2003). The specific name honours Thomas Burke, a wildlife biologist who has worked extensively on terrestrial gastropods of the Pacific Northwest of the United States.

Morphological description

As its common name implies, Pygmy Slug is very small with adults usually 9 - 14 mm in extended length (Leonard et al.. 2003). In British Columbia (BC), the length of slugs when measured live ranged from 3 - 16 mm, including juveniles (Ovaska and Sopuck, unpubl. data 2007 - 2015). The body is slender, and the mantle covers approximately half of the length of the animal (Figure 1). The tail is rounded (lacking a keel) with a series of parallel and oblique longitudinal grooves. The grooves branch at the tip of the tail, forming small polygons, which are characteristic of the species (Burke 2013). The grooves on the tail may resemble thin dark stripes. It lacks an abscission line, such as found in taildroppers (Prophysaon species).

Figure 1. Pygmy Slug, Kootenaia burkei, from British Columbia. The length of the slug is ca. 10 mm.
Pygmy Slug
Photo: © K. Ovaska.
Long description for Figure 1

Photo of a Pygmy Slug on a leaf (dorsal view). Adult Pygmy Slugs are small (usually 9 to 14 millimetres long). The colour ranges from dark grey to tan with dense bluish flecking covering the mantle and tail; dark mottling is often present on the mantle. The body is slender, and the mantle covers approximately half of the length of the animal. The tail is rounded (lacking a keel) with a series of parallel and oblique longitudinal grooves, which may resemble thin dark stripes.

The colour is from dark grey to tan with dense bluish flecking covering the mantle and tail. Dark mottling is often present on the mantle but is occasionally lacking (Leonard et al. 2003). In BC, only unmottled slugs were found at some sites, whereas at most sites only mottled slugs were found (Ovaska and Sopuck, unpubl. data 2007 - 2015).

Internally, Pygmy Slug differs from other arionid slugs by its distal reproductive anatomy, commonly used in the classification and identification of gastropods. Compared to other arionids, it has an unusually reduced male component of the reproductive system and lacks a free epiphallus or vas deferens (Leonard et al.. 2003).

Population spatial structure and variability

Genetic structure of Pygmy Slug populations is unknown. In BC, the species is known from scattered localities, most of which are south of 49.4°N. These and the more northern localities (up to 50.5°N) are separated by a minimum distance of 58 km (between Sites 4 and 6), and relatively great distances also separate the four northernmost localities from each other (42 km between Sites 5 and 9; 29 km between Sites 9 and 10; 38 km between Sites 10 and 4). Slugs in the northern localities are most likely isolated from each other and from those from farther south. Given the limited dispersal capabilities of the slugs and their affinity for very moist habitats, it is unlikely that there would be much genetic exchange among subpopulations outside single creeks or sub-drainages even within the southern portion of the range, where the species' distribution may be more continuous.

Designatable units

Pygmy Slug is known from a relatively small area within one COSEWIC National Ecological Area (Southern Mountain). There are no range disjunctions or other information that would suggest the presence of separate discrete and evolutionarily significant units within the Canadian subpopulation, but the genetic, anatomical, or ecological variability within the species has not been studied. The species is treated as one designatable unit.

Special significance

Pygmy Slug is a regional endemic to moist forests of the northern Columbia Basin, an area that contains many unique plants and animals (Brunsfeld et al. 2001). This area extends from southeastern BC and northeastern Washington through the Idaho Panhandle to northwestern Montana. As one of a few genera of slugs endemic to western North America and the only representative of its genus, this species is of scientific interest for the study of glacial history and evolutionary relationships.


Distribution

Global range

The global distribution of Pygmy Slug extends from southeastern BC through the Idaho Panhandle to northwestern Montana (Figure 2). On the Idaho Panhandle, the species has been reported from seven localities (five localities, Leonard et al.. 2003; Leonard pers. comm. 2013; two localities, Hendricks and Maxwell 2005; Hendricks pers. comm. 2013). There are 25 observations for Pygmy Slug in the Montana Natural Heritage Program database (current up to 11 April 2013; Montana Government 2013). These are from Lincoln, Sanders, and Mineral counties in the northwest of the state. Although there are no records, the species may occur in the extreme northeast of Washington State, based on the proximity of records to the British Columbia border. In Canada, the species has been found only in the Kootenay region of BC. Approximately 36% of the species' range is in Canada.

Figure 2. Global distribution of Pygmy Slug, Kootenaia burkei. Data sources: Leonard et al. (2003); Hendricks and Maxwell (2005); Hendricks pers. comm. (2013); Montana Government (2013); Table 1 (Canadian records).
Global distribution
Map: © Prepared by Lennart Sopuck and Jenny Wu.
Long description for Figure 2

Map of the global distribution of the Pygmy Slug, which extends from southeastern British Columbia through the Idaho Panhandle to northwestern Montana.

Table 1. Distribution records for Pygmy Slug, Kootenaia burkei, from Canada.
Site #Site descriptionElev. (m)BEC Zone Table Footnote aDate# slugs foundSearch time (pers. min.)HabitatAppr. stand age (yrs)Source Table Footnote b
1Lost Creek (rest area), off HWY3 between Salmo & Creston, BC664ICHxw (near border with ICHdw1)22-Sep-071118Second-growth mixed-wood forest; riparian forest along river50Ovaska and Sopuck 2009a (RBCM uncatalogued)
2Hawkins Creek, Yahk Meadow FSR, ca. 3 km from Yahk, BC913ICHdw123-Sep-078132Second-growth mixed-wood forest; riparian floodplain along creek80Ovaska and Sopuck 2009a (RBCM 007-00077-001)
3Yahk River FSR, along tributary of Sunrise Creek, BC1260ICHdm05-Sep-08170Second-growth coniferous forest; riparian forest along dried-up creek50-100Ovaska and Sopuck 2009a (photos)
4Lemon Creek, Slocan Valley, BC705ICHdw103-Sep-08370Second-growth mixed-wood forest; riparian area along creek60Ovaska and Sopuck 2009a (photos)
5Halfway River FSR, South of Galena (east of Arrow Lake), BC781ICHmw208-Oct-082124Older mixed-wood forest; riparian area along creek100Ovaska and Sopuck 2009a (photos)
6Marsh Creek Rd, off Champion Park Rd (off HWY 3), between Fruitvale and Salmo BC1090ICHdw109-Oct-081120Older mixed-wood forest; edge of small forest gap in a moist depression-Ovaska and Sopuck 2009a (photos)
7Sundown Cr. FSR (spur), ca. 5 km SE from Moyie, BC975ICHdw18-Oct-09160Second-growth mixed-wood forest; moist riparian area along creek70Ovaska and Sopuck 2009b (photos)
8Sundown Cr, SW of Moyie, BC1140ICHdw111-Sep-1016123Second-growth mixed-wood forest; seepage area by small creek50Ovaska et al. 2010 (RBCM uncatalogued)
9Slewiskin (McDonald) FSR (Site 2), S of Nakusp, BC640ICHmw222-Sep-13160Second-growth mixed-wood forest; along fast-flowing tributary creek60-70Fieldwork in support of this status report by K. Ovaska and L. Sopuck (RBCM uncatalogued)
10East Wilson Cr. FSR (Site 2), N of New Denver, BC581ICHdw122-Sep-13160Second-growth mixed-wood forest along fast-flowing tributary creek40-50Fieldwork in support of this status report by K. Ovaska and L. Sopuck (RBCM uncatalogued)
119 Mile Cr. (Site 2B), Pend d'Oreille, BC608ICHxw23-Sep-13160Older coniferous forest; moist forest along creek100+Fieldwork in support of this status report by K. Ovaska and L. Sopuck (RBCM uncatalogued)
12Sheep Cr. FSR (Site 1), S of Salmo, BC1179ICHmw224-Sep-13350Older mixed-wood forest; riparian forest along fast-flowing tributary creek100+Fieldwork in support of this status report by K. Ovaska and L. Sopuck (RBCM uncatalogued)
13Sheep Cr. FSR (Site 2), S of Salmo, BC969ICHdw124-Sep-13240Second-growth mixed-wood forest; riparian area along fast-flowing creek80Fieldwork in support of this status report by K. Ovaska and L. Sopuck (RBCM uncatalogued)
14Carroll Cr. Road, W of Yahk, BC993ICHdw124-Sep-13150Old-growth coniferous forest; moist area along creek200+Fieldwork in support of this status report by K. Ovaska and L. Sopuck (RBCM uncatalogued)
15Teepee Cr. FSR, SE of Cranbrook, BC1125MSdk1 (near border with ICHmk4)25-Sep-13940Older coniferous forest; moist creek-side100Fieldwork in support of this status report by K. Ovaska and L. Sopuck (RBCM uncatalogued)
16Meachen Cr. FSR (Site 3 at Fiddler Cr.), ca. 14 km S of Mary's Lake, BC1284ESSFwm18-Sep-14440North-facing sloping side of ravine with young cottonwoods along fast-flowing tributary creek60-70MoE 2014 & fieldwork for COSEWIC report for Sheathed Slug Table Footnote c (RBCM uncatalogued)
17Hellroaring Cr. FSR (Site 1), S. of St. Mary's Lake, BC1304ESSFwm18-Sep-14160Cottonwood fringe along road in steep mid-slope mainly coniferous forest60-70MoE 2014 & fieldwork for COSEWIC report for Sheathed Slug Table Footnote c (RBCM uncatalogued)
18Cherry Cr. FSR (Site 3), near Cherry Lake, BC1229ICHdm/ MSdk1 border (right on border)20-Sep-14250Alluvial flat with alders by stream in coniferous forest, perhaps seasonally flooded80-90MoE 2014 & fieldwork for COSEWIC report for Sheathed Slug Table Footnote c (RBCM uncatalogued)
19Bloom Cr. FSR (Site 3), BC1269MSdk120-Sep-14160Riparian area with alders along small stream (trickle of water) in second growth forest60MoE 2014 & fieldwork for COSEWIC report for Sheathed Slug Table Footnote c (RBCM uncatalogued)
20Yahk R FSR (Site 3), BC1111MSdk121-Sep-14140Moist, periodically flooded alluvial site along fast-slowing larger stream; canopy gap in coniferous forest with abundant understorey vegetation100MoE 2014 & fieldwork for COSEWIC report for Sheathed Slug Table Footnote c (RBCM uncatalogued)
21Lamb Cr. FSR (Site 1), W of Moyie, BC1121ICHdm22-Sep-14140Moist riparian floodplain in narrow ravine within landscape of shelter wood logging; several very large cottonwoods70MoE 2014 & fieldwork for COSEWIC report for Sheathed Slug Table Footnote c (RBCM uncatalogued)
22Tate Cr. FSR (Site 1),off Lamb Cr. FSR, BC1194ICHdm22-Sep-14540Riparian buffer (50-75m wide) with large cottonwoods in rich floodplain along creek80MoE 2014 & fieldwork for COSEWIC report for Sheathed Slug Table Footnote c (RBCM uncatalogued)
23Tate Cr. FSR (Site 2),off Lamb Cr. FSR, BC1392ICHdm22-Sep-14250Forested ravine along small creek (riparian zone <20 m) surrounded by upland old coniferous forest150MoE 2014 & fieldwork for COSEWIC report for Sheathed Slug Table Footnote c (RBCM uncatalogued)
24Irishman R. FSR, near Moyie, BC971ICHdw122-Sep-14140Older moist coniferous forest with little understorey except in canopy gaps125+MoE 2014 & fieldwork for COSEWIC report for Sheathed Slug Table Footnote c (RBCM uncatalogued)
25Cold-Freeman FSR (Site 2), off Hawkins FSR, E of Yahk, BC1179ICHdm23-Sep-14240Moist riparian area along creek with hummocks and depressions and cottonwoods in second-growth coniferous forest70-80MoE 2014 & fieldwork for COSEWIC report for Sheathed Slug Table Footnote c (RBCM uncatalogued)
26Skelly Cr FSR (Site 1), off Goat Cr. FSR, NE of Creston, BC944ICHdw124-Sep-14140Riparian floodplain along creek with cottonwoods in second-growth mainly coniferous forest60-70MoE 2014 & fieldwork for COSEWIC report for Sheathed Slug Table Footnote c (RBCM uncatalogued)
27Skelly Cr FSR (Site 2), off Goat Cr. FSR, NE of Creston, BC1095ICHdm24-Sep-14156Narrow (ca 10 m wide) riparian zone along fast-flowing tributary creek, surrounded by dense second-growth coniferous forest with little understorey40-50MoE 2014 & fieldwork for COSEWIC report for Sheathed Slug Table Footnote c (RBCM uncatalogued)
28Goat R FSR (Site 2), NE of Creston, BC1092ICHdw124-Sep-14140Moist depression in second-growth (ca. 60-70 year old) forest60-70MoE 2014 & fieldwork for COSEWIC report for Sheathed Slug Table Footnote c (RBCM uncatalogued)
29Mt. Thompson FSR (Site 1), E of Creston, BC855ICHxw24-Sep-14154Moist riparian area with cottonwoods along fast-flowing creek in otherwise dry coniferous slope with little understorey90-100MoE 2014 & fieldwork for COSEWIC report for Sheathed Slug Table Footnote c (RBCM uncatalogued)
30Sanca Cr FSR (Site 1), N of Creston, BC1189ICHdw125-Sep-14540Narrow (ca 10 m wide) riparian zone along fast-flowing tributary creek in otherwise dry, pine-dominated landscape; rare, moist area40MoE 2014 & fieldwork for COSEWIC report for Sheathed Slug Table Footnote c (RBCM uncatalogued)
31Sanca Cr FSR (Site 4; South Fork), N of Creston, BC1585ESSFdm25-Sep-14140Moist riparian area on floodplain along stream in older coniferous forest; abundant blowdown and big boulders100+MoE 2014 & fieldwork for COSEWIC report for Sheathed Slug Table Footnote c (RBCM uncatalogued)
32Dodge Cr. FSR (Site 2) at Dodge Cr, S of Creston, BC1325ICHmw426-Sep-14180Riparian zone with some cottonwoods in young forest; landscape is otherwise dry with clearcutting and only a few creeks30-40MoE 2014 & fieldwork for COSEWIC report for Sheathed Slug Table Footnote c (RBCM uncatalogued)
33Monk Cr FSR (site 1)1411ESSFdm27-Sep-14260Moist older coniferous forest with productive deep soil and shrubs in swale100+MoE 2014 & fieldwork for COSEWIC report for Sheathed Slug Table Footnote c (RBCM uncatalogued)
34HWY 6 to Nelway (small spur), S of Salmo, BC668ICHdw127-Sep-14; 24 Sep-158; 8126; 60Moist riparian area along stream in second-growth coniferous forest40-60MoE 2014, 2015 & fieldwork for COSEWIC report for Sheathed Slug Table Footnote c (RBCM uncatalogued)
35Champion Lakes (Site 2), N of Trail, BC1079ICHdw128-Sep-14140Older coniferous forest with abundant well-decayed moist wood and patches of shrubs in moist depressions100+MoE 2014 & fieldwork for COSEWIC report for Sheathed Slug Table Footnote c (RBCM uncatalogued)
36Archibald - Tillicum FSR (Site 2), SW of Salmo, BC1229ICHdw129-Sep-14; 24 Sep-155; 550; 120Moist riparian zone with cottonwoods along small creek within logged landscape in second-growth forest50-60MoE 2014, 2015 & fieldwork for COSEWIC report for Sheathed Slug (RBCM uncatalogued)
37Erie Cr FSR (Site 1), N of Erie, NW of Salmo, BC991ICHdw129-Sep-14240Moist ravine with cottonwoods along small creek within landscape of dry, younger (logged) forest60-70MoE (Ovaska and Sopuck 2014) & fieldwork for COSEWIC report for Sheathed Slug Table Footnote c (RBCM uncatalogued)
38Erie Cr FSR (Site 2), N of Erie, NW of Salmo, BC915ICHdw129-Sep-14140Moist riparian floodplain with alder in older coniferous forest100+MoE (Ovaska and Sopuck 2014) & fieldwork for COSEWIC report for Sheathed Slug Table Footnote c (RBCM uncatalogued)
39Beaver Lookout Rd (off Archibald -Tillicum FSR), BC987ICHdw124 Sep-15262Riparian area by side of fast-flowing creek; small moist, shrubby clearing between road & creek40-50MoE (Ovaska and Sopuck 2015); (RBCM uncatalogued)
40Elmer Creek FSR, SE of Creston, BC1013ICHdw124 Sept-15390Riparian area along small fast-flowing tributary stream40-50MoE (Ovaska and Sopuck 2015); (RBCM uncatalogued)
41American Creek FSR, off Hawkin Cr, Meadow Rd, E of Yahk, BC1135ICHdm25 Sept-15160Canopy gap with abundant herbaceous growth on sloping terrain in moist forest; seepage area on slope60-70MoE (Ovaska and Sopuck 2015); (RBCM uncatalogued)
42Randal Creek FSR, S off Hawkin Cr FSR1327ICHdm25 Sept-15290Moist grassy slope in forest gap (~30 m upslope from small creek/depression)50-60MoE (Ovaska and Sopuck 2015)
43West Yahk Road, E of Yahk1189ICHdm25 Sept-15390Moist bench between two streams in older forest80-90MoE (Ovaska and Sopuck 2015); (RBCM uncatalogued)
44West Yahk Road (Site 3), E of Yahk1223ICHdm25 Sept-15260Riparian habitat along trickling creek in forest patch50-60MoE (Ovaska and Sopuck 2015); (RBCM uncatalogued)

Table Footnote

Footnote 1

Biogeoclimatic Zone (Meidinger and Pojar 1991); ESSF - Engelmann Spruce/Subalpine Fir; ICH - Interior Cedar/Hemlock; MS - Montane Spruce; subzones: ESSF: dm - Dry Mild; wm - Wet Mild; ICH: dm - Dry Mild; dw1 - West Kootenay Dry Warm; mw2 - Shuswap Moist Warm; mk - Moist Cool; mw4 - Ymir Moist Warm; xw - Very Dry Warm; MS: dk - Dry Cool

Return to Footnote a referrer

Footnote 2

MoE-BC Ministry of Environment; RBCM-Royal British Columbia Museum; RBCM uncatalogued - catalogue number to be assigned

Return to Footnote b referrer

Footnote 3

Surveys conducted by K. Ovaska and L. Sopuck for BC Ministry of Environment (MoE) and in support of the preparation of COSEWIC status report for the Sheathed Slug (Zacoleus idahoensis), which occurs in similar habitats as Pygmy Slug.

Return to Footnote c referrer

Canadian range

In Canada, Pygmy Slug occurs in the Selkirk and Purcell sub-ranges within the Columbia Mountains in southeastern BC (Figure 3). Its range lies between the east arm of the Columbia River (Lake Koocanusa) in the east and the Arrow Lakes in the west. The northernmost record (50.5 N°) is 62 km southeast of Revelstoke on the east side of Upper Arrow Lake.

Figure 3. Canadian distribution of Pygmy Slug. Source of records from Table 1.
Canadian distribution of Pygmy Slug
Map: © Prepared by Jenny Wu, COSEWIC Secretariat
Long description for Figure 3

Map of the distribution of the Pygmy Slug in Canada, where it occurs in the Selkirk and Purcell sub-ranges within the Columbia Mountains in southeastern British Columbia. Its range lies between the east arm of the Columbia River (Lake Koocanusa) in the east and the Arrow Lakes in the west. The northernmost record (50.5 degrees north) is 62 kilometres southeast of Revelstoke on the east side of Upper Arrow Lake.

Pygmy Slug was first discovered in BC in 2007, and subsequent targeted surveys from 2008 - 2015 have documented additional localities. There are now records from 44 sites in BC (sites are defined as localities >1 km from each other; Table 1). All but four sites are from below 49.58°N and within 64 km north of the international border. New sites continue to be found with increasing search effort; seven new sites were found in September 2013, 23 in 2014 as part of targeted surveys associated with the preparation of this status report and that for the Sheathed Slug, Zacoleus idahoensis, respectively, and six were found in 2015 during additional surveys for the BC Ministry of Environment, but the boundaries of the known range did not increase significantly. Additional sites are likely to exist, especially within the southern portion of the species' range.

Extent of occurrence and area of occupancy

Using the minimum convex polygon method based on known occurrence records, the extent of occurrence (EOO) is 15,552 km2 with the international border with the United States as the southern boundary of the polygon.

The index of area of occupancy (IAO) based on a discrete grid for each observation record or group of records, is 180 km2 (45 2 x 2 km grid cells). A more realistic IAO may be obtained by considering the entire creek with records of the species. Using this method, the continuous IAO is 1160 km2 (290 2 x 2 grid cells) (EOO and IAO calculations by Jenny Wu, COSEWIC Secretariat). Additional, undocumented sites may exist that could further expand the IAO.

Search effort

Little information exists on survey effort from the Kootenay region in BC before the 1990s. In his review of terrestrial gastropods of the Columbia Basin, Forsyth (1999) reported only four brief accounts that included terrestrial molluscs (from 1905 - 1945). Since the early 1990s, extensive surveys have been carried out in the Kootenay region, and over 700 sites have been surveyed (Table 2 ; Figure 4.). Most of these surveys specifically targeted terrestrial gastropods, with the exception of those by Copley and Copley, which were general arthropod surveys in which all gastropods encountered were collected and subsequently identified. Surveys have been carried out mostly in autumn, which generally is the best time for locating terrestrial gastropods, especially slugs; at this time, conditions are favourable for gastropod activity (wet and mild) and most slugs are mature, facilitating their detection.

Pygmy Slug was first found by Biolinx Environmental Research Ltd. in 2007; their surveys in subsequent years (2008, 2009, 2010, 2013, 2014, and 2015) resulted in further records for the species. Surveys in September 2013 and 2014 were in support of the preparation of this status report and that of the Sheathed Slug, respectively, and focused on habitats of Pygmy Slug; the Sheathed Slug occurs in similar habitats (see Appendix 1 for survey sites and species found). In an attempt to better delineate the Pygmy Slugs' distribution in BC in 2013, areas outside its known range to the west, north, and east were surveyed, progressing inward towards the presumed core range in the West Kootenays. The surveys in 2013 resulted in seven and those in 2014 in 23 new records for Pygmy Slug (Sites 9 - 38 in Table 1 and Figure 3) but only marginally increased the EOO. Additional surveys supported by the BC Ministry of Environment in 2015 (Ovaska and Sopuck 2015) resulted in six new sites but did not expand the EOO.

Table 2. Summary of survey effort for terrestrial gastropods in southeastern British Columbia. Number of non-overlapping survey sites were calculated from GIS maps within the area of interest delineated in Figure 4.
YearMonths# sitesSearch timeSurveys conducted by:Source or project Table Footnote d
1998-1999September (1 in July)40-RBCM (Kelly Sendall, Phil Lambert)Living Landscape project; RBCM files
1990-2013Various135-Robert ForsythR. Forsyth personal main database (current up to 2013) and other unique sites; includes Flathead Bioblitz 2012
2007July, September6366.1 person-hoursBiolinx Environmental Research Ltd (Kristiina Ovaska, Lennart Sopuck)Ovaska and Sopuck 2009a
2008September, October4548 person-hoursBiolinx Environmental Research Ltd (Kristiina Ovaska, Lennart Sopuck)Ovaska and Sopuck 2009a
2009October1720.9 person-hoursBiolinx Environmental Research Ltd (Kristiina Ovaska, Lennart Sopuck)Ovaska and Sopuck 2009b
2009-2013July - September96-Claudia and Darren CopleyC. Copley data files
2008-2011Various85-Dwayne LepitzkiSurveys in Alberta and BC; Lepitzki personal database
2010September5667.9 person-hoursBiolinx Environmental Research Ltd (Kristiina Ovaska, Lennart Sopuck)Ovaska et al. 2010
2011August, September29-Jeff Nekola, Brian Coles, Michael HorsekSurveys for Valhalla Wilderness Society; Nekola et al. 2011
2012August6-Melissa FreyFlathead Bioblitz; RBCM database; Note: additional sites that overlap with those of Forsyth are excluded.
2013September3631.7 person-hoursBiolinx Environmental Research Ltd (Kristiina Ovaska, Lennart Sopuck)Fieldwork associated with the preparation of COSEWIC status report for Pygmy Slug
2013June14-Dwayne & Brenda LepitzkiFlathead Bioblitz; Lepitzki data files
2014September7272.2 person-hoursKristiina Ovaska & Lennart SopuckGastropod surveys for BC Ministry of Environment and fieldwork associated with the preparation of COSEWIC status report for the Sheathed Slug
2015September36 Table Footnote e38.5 person-hoursBiolinx Environmental Research Ltd (Kristiina Ovaska, Lennart Sopuck)Gastropod surveys for BC Ministry of Environment (Ovaska and Sopuck 2015)

Table Footnote

Footnote 4

MoE-BC Ministry of Environment; RBCM-Royal British Columbia Museum

Return to Footnote d referrer

Footnote 5

6 sites were revisits to sites where Pygmy Slug or Sheathed Slug had been found previously.

Return to Footnote e referrer

Figure 4. Overview of sites surveyed for gastropods in and around the range of Pygmy Slug in southeastern British Columbia (see Table 2 for data sources within the area of interest).
Overview of sites surveyed for gastropods
Map: © Prepared by Lennart Sopuck
Long description for Figure 4

Map showing the locations of sites (symbols) surveyed for gastropods in and around the range of the Pygmy Slug in southwestern British Columbia from 1990 to 2015.


Habitat

Habitat requirements

Across its global range, Pygmy Slug occurs in moist mixed-wood and coniferous forests, particularly in riparian habitats (Leonard et al.. 2003; Hendricks and Maxwell 2005; Ovaska and Sopuck 2009a,b). Leonard et al.. (2003) mentioned the close proximity of occupied sites to perennial water bodies, presumably because they contain suitable moist substrates. A predicted distribution model for Montana, based on the analysis of biophysical features at 20 known points and 60,000 random background points, showed that high suitability habitat was largely restricted to strips of riparian habitat along watercourses (Montana Government 2013). Observations in BC are also mostly from riparian habitats, frequently along fast-flowing creeks (Table 1). The riparian zone along these creeks was often confined to narrow strips in gullies, but in some cases the slugs were found in more expansive seepage areas with flatter terrain. Common understorey plants at occupied sites included Thimbleberry (Rubus parviflorus), Devil’s Club (Oplopanax horridum), Lady Fern (Athyrium filix-femina), Wild Sarsaparilla(Aralia nudicaulis), Twinflower (Linnea borealis), and Foamflower (Tiarella trifoliata). The slugs are not inhabitants of open shorelines or wetlands, such as Cattail (Typha latifolia) marshes.

Pygmy Slug occurs from low to mid-elevations in Idaho (640 m - 700 m asl (above sea level); Leonard et al. 2003), Montana (762 m - 1372 m asl for most records; reported as 2500’ - 4500’; Montana Government 2013), and BC (571 m - 1585 m asl; Table 1). Thirty six of the 44 (81.8%) Canadian records are from the Interior Cedar - Hemlock (ICH) Biogeoclimatic Zone (see Meidinger and Pojar 1991 for the classification of zones). Two sites are from the Montane Spruce (MS), two from the border of ICH and MS, and four from the Engelmann Spruce - Sub-alpine Fir (ESSF) zone (Table 1). The ICH zone occurs from low to mid-elevations in the lower slopes of the Columbia Mountains in southeastern BC, extending south to eastern Washington, Idaho Panhandle, and western Montana (Ketcheson et al.. 1991). It is flanked from above along an elevational gradient by the ESSF zone. The ICH zone is characterized by cool, wet winters and warm, dry summers with much of the soil moisture derived from snowmelt. The growing season (with above 0°C temperatures) extends from two to five months, depending on the latitude and elevation. It is among the wettest interior BC zones, sharing features with moist coniferous forests along the Pacific Coast; it is sometimes referred to as the Interior Wet Belt. Productive upland coniferous forests are prevalent throughout the landscape, but topography and soil conditions have resulted in a mosaic of wetter and drier forest types with relatively high over- and understorey diversity.

In BC, Pygmy Slug has been found in mixed-wood and coniferous forest stands of varying ages, ranging from 40 - 50-year-old second growth to old growth (>200 years old) stands (Table 1). Western Redcedar (Thuja plicata) was present in 74%, Black Cottonwood (Populus trichocarpa) in 61%, Engelmann Spruce (Picea engelmannii) in 58%, and Western Hemlock (Tsuga heterophylla) in 42% of the 38 occupied sites. Other tree species included Grand Fir (Abies grandis), Amabilis Fir(Abies amabilis), Subalpine Fir(Abies lasiocarpa), Paper Birch (Betula papyrifera), Western Larch (Larix occidentalis), and rarely Lodgepole Pine (Pinus contorta). A moderate understorey of diverse shrubs was usually present and often included moisture-loving species, such as Thimbleberry and Devil’s Club. Pockets of deeper leaf litter or relatively large amounts of coarse woody debris (mean = 14% coverage within 10 m from slug observations) were usually present (Ovaska and Sopuck, unpubl. data 2007 - 2014). Slugs were found in leaf litter, frequently within wet Cottonwood leaves, or under woody debris on the forest floor in moist situations. Common features among the sites included very moist substrates and abundant cover for the slugs to seek refuge. The availability of these microhabitat features may exert an overriding influence on the forest type or other coarse-scale habitat features.

Habitat trends

Within the Pygmy Slug’s Canadian range, most suitable habitats are on provincial and private forestry lands subjected to ongoing logging. The removal of tree cover, building of forestry roads, and silvicultural activities associated with forestry have had the greatest impact on the availability of habitat within the species’ range, and logging continues to fragment and alter habitats. Ninety five percent of the known Pygmy Slug sites are within landscapes with ongoing logging (see Threats).

The Annual Allowable Cut (AAC) established for Crown lands on the three Timber Supply Areas encompassing the species’ range (Arrow, Kootenay Lake, and Cranbrook) has been relatively constant over the past four decades (MFLNRO 2014a). The latest AAC for these Timber Supply Areas, covering the next 5 - 10 years, suggests that a slightly lower level of harvest will be maintained. Most of the timber harvested in the past was from old-growth and from maturing forests on naturally disturbed areas. In the future, a greater proportion of the harvest will be obtained from regenerating second growth stands. In areas where the forest was logged 50 - 60 years ago (mainly lower to mid-elevations), conditions in maturing forests may allow the slugs to re-colonize some previously logged areas. Such increases in habitat availability will only partially compensate for the continuing degradation of habitat from logging. It is important to note, however, that logging does not occur, or is restricted, in parks, conservation lands, near fish-bearing streams, community watersheds, old-growth management areas, and special resource management zones that are scattered throughout the slugs’ range. The available land base for harvest for the Kootenay Lake Timber Supply Area, which encompasses over half of the slugs’ range, is estimated at 42% of productive forest land, after accounting for these conservation areas and other constraints to logging (MFLNRO 2014b). Additional timber is harvested each year on private lands and by woodlot licensees on Crown land (quantitative information could not be found).

Livestock grazing on Crown forest lands is confined mainly to the drier southern and eastern portions of the species’ range (iMapBC 2014). Range tenures on Crown lands are managed to avoid excessive grazing, potentially reducing impacts on riparian areas.

Land conversions for residential and industrial developments and for agriculture have resulted in the permanent loss of slug habitat mainly on private land at lower elevations, especially along river valleys, lake shores, and highways. However, the population density of the West Kootenay region is relatively low compared to other areas of southern BC, such as the Okanagan Valley and eastern Columbia Basin. Since 2001, the human population in the West Kootenay region has increased at a rate of only 1.3% per decade, reaching 64,379 people in 2011 (Columbia Basin Rural Development Institute 2012). Large population centres within the species’ range occur at Nelson and Creston, and a few much smaller communities occur at Fruitvale, Kaslo, Nakusp, Slocan Valley, Moyie Lake and Yahk. The relatively large cities of Castlegar, Trail, and Cranbrook lie just outside the species’ range.

Mining and quarrying activities are also present but involve a small percentage of the Pygmy Slug’s range. Mining and placer claims are common throughout the species’ range, especially in the south (Trail, Nelson, Salmo, Moyie Lake), and central (New Denver/Silverton) areas, and several mineral exploration projects are underway (Grieve 2010). Although new mines could be developed in the future, no mining projects are currently being assessed in the slugs’ range (iMapBC 2014). However, immediately to the northeast near Trout Lake, the reopening and expansion of a mine for the mineral molybdenum is under review. Extensive habitat degradation from air pollution has occurred over the last 100 years in the vicinity of the smelter in Trail, on the periphery of the species’ range.

Reservoirs associated with hydroelectric development have flooded large areas of potential slug habitat over the past century (Kootenay Lake and Pend D’Oreille within the range; Arrow Lakes, Duncan Lake, and Lake Koocanusa on the periphery). Several projects are underway to upgrade hydro power stations, but no large-scale creation or expansion of reservoirs are planned in the near future (iMapBC 2014). Power transmission line corridors are relatively common in the species’ range and several more will likely be built to serve expanded hydro operations. Over 20 smaller-scale run-of river hydroelectric projects are also proposed or approved (1 is operational, 8 are approved and the remainder are under review) within the species’ range (Wildsight 2014).

Recreational developments such as ski areas, tourist resorts and campgrounds are scattered over the Pygmy Slug’s range, but infrastructure is limited at present. No large tourist developments are currently being assessed for the area (iMapBC 2014). The proposed Jumbo Glacier Resort development is located northeast of the species’ range. Widespread recreational activities in the area include use of all-terrain vehicles, snowmobiles, and mountain bikes.

Previous and ongoing habitat fragmentation due to all human activities combined, especially at lower elevations, is a concern for Pygmy Slug. Fragmentation has occurred as a result of extensive logging, increased frequency of catastrophic wildfires (due to buildup of fuels to unnatural levels), the creation of large hydroelectric reservoirs, highway construction, urbanization, and land conversions for agriculture. The ICH biogeoclimatic zone is prone to periodic fire disturbance but to a lesser degree than drier biogeoclimatic zones in the southern interior of BC (Biodiversity Guidebook 1995). Logging on the other hand selectively removes high-value timber in moist, productive sites, resulting in fewer refuges being available to slugs after logging.

Climate change

The West Kootenay Resilience Program (undated) has produced a series of documents addressing climate change and its implications in the West Kootenay region of British Columbia. Pygmy Slug occurs mainly in the south and middle subzones of the West Kootenays, and along the southern fringe of the north subzone. All models and scenarios examined project higher mean seasonal temperatures that increase progressively by 2020s, 2050s and 2080s (Utzig 2012a). By 2080, winters are predicted to be 2 - 5 C° warmer and 10 - 25% wetter and summers 3 - 7°C warmer and up to 30% drier than during the baseline period (poorest performance models excluded). Associated changes that have implications for Pygmy Slug include increase in summer moisture stress, potential increase in wildfires and insect and disease outbreaks that would reduce forest cover, and changes in seasonal stream flow patterns as a result of reduced snow-packs and summer droughts, which would alter the riparian areas inhabited by the slugs. Increase in the magnitude and frequency of extreme events, such as high intensity rain events, severe droughts, and wind storms, are also predicted (Utzig 2012a).

Wang et al. (2012) examined climate change effects on BC’s 16 biogeoclimatic zones, which are based on large-scale climate gradients and widely used to classify ecosystems in the province (Meidinger and Pojar 1991). Models showed that climate envelopes supporting this zonation have already shifted since the 1970s (Wang et al. 2012). Projected into the future (2020s, 2050s, and 2080s) and across the entire province, the models predict a substantial expansion of moist continental cedar-hemlock forests, typical of the ICH zone where Pygmy Slug is found, potentially expanding this zone up to three-fold by 2080, with the ICH zone becoming the most common forest type in the province over the long term (Wang et al.. 2012). At a regional scale, the projections are more complex and influenced by topography and local factors (Utzig 2012b). Climate models for the West Kootenays indicate that the ICH zone will expand over the long term under one of three climate change scenarios examined (“Warm/Moist” scenario), while it is predicted to be largely displaced by the Coastal Western Hemlock and Coast Transition-type ecozones, which also consist of moist forests, under the “Hot/Wet” scenario, and by the drier Grassland-steppe and Ponderosa Pine woodlands under the “Very Hot/Dry” scenario (Table 3.1 and Figure 3.5 in Utzig 2012b). The expansion of moist and wet forest types favourable to Pygmy Slug are mostly in the northern portion of the species’ range and/or at higher elevations (>1000 m asl). Correspondingly, suitable habitat would shrink in the southern portion of the range and at lower elevations. Whether Pygmy Slug would be able to spread northwards and upwards in pace with the ecosystem shifts to take advantage of the newly available habitats is questionable. The changes may be driven largely by extreme climatic events such as summer droughts or storms and mediated through pest outbreaks, fires or other disturbances rather than occurring through gradual transition (Pojar 2010; Utzig 2012b); also, novel bioclimatic zones may emerge with new combinations of seasonal climatic variables (Utzig 2012b), increasing the unpredictability of the projections.

Table 3 Assessment date
5 Feb-2014
Table 3. Summary of IUCN threats calculator assessment for Pygmy Slug. Those threat categories that were not applicable to the species are omitted (hence the numbering of threats has gaps).
Threat ImpactThreat Impact (descriptions)Level 1 Threat Impact Counts:
high range
Level 1 Threat Impact Counts:
low range
AVery High00
BHigh00
CMedium20
DLow46
-Calculated Overall Threat Impact:HighMedium
Threats Assessment Worksheet Table.
#ThreatImpact
(calculated
Impact
(description)
Scope
(next
10 Yrs)
Severity
(10 Yrs
or
3 Gen.)
Timing
1Residential and commercial development-NegligibleNegligible (<1%)Extreme (71-100%)High (Continuing)
1.1Housing and urban areas-NegligibleNegligible (<1%)Extreme (71-100%)High (Continuing)
1.2Commercial and industrial areas-NegligibleNegligible (<1%)Extreme (71-100%)High (Continuing)
1.3Tourism and recreation areas-NegligibleNegligible (<1%)Serious (31-70%)Moderate (Possibly in the short term, < 10 yrs/3 gen)
2Agriculture and aquacultureDLowSmall (1-10%)Moderate - Slight (1-30%)High (Continuing)
2.1Annual and perennial non-timber crops-NegligibleNegligible (<1%)Serious (31-70%)High (Continuing)
2.3Livestock farming and ranchingDLowSmall (1-10%)Moderate - Slight (1-30%)High (Continuing)
3Energy production and mining-NegligibleNegligible (<1%)Extreme - Serious (31-100%)Moderate (Possibly in the short term, < 10 yrs/3 gen)
3.2Mining and quarrying-NegligibleNegligible (<1%)Extreme - Serious (31-100%)Moderate (Possibly in the short term, < 10 yrs/3 gen)
4Transportation and service corridorsDLowSmall (1-10%)Moderate - Slight (1-30%)High (Continuing)
4.1Roads and railroadsDLowSmall (1-10%)Moderate - Slight (1-30%)High (Continuing)
4.2Utility and service lines-NegligibleNegligible (<1%)Moderate (11-30%)High (Continuing)
5Biological resource useDLowRestricted (11-30%)Moderate (11-30%)High (Continuing)
5.2Gathering terrestrial plants-NegligibleRestricted - Small (1-30%)Negligible (<1%)High (Continuing)
5.3Logging and wood harvestingDLowRestricted (11-30%)Moderate (11-30%)High (Continuing)
6Human intrusions and disturbance-NegligibleRestricted (11-30%)Negligible (<1%)High (Continuing)
6.1Recreational activities-NegligibleRestricted (11-30%)Negligible (<1%)High (Continuing)
7Natural system modificationsDLowSmall (1-10%)Moderate (11-30%)High (Continuing)
7.1Fire and fire suppressionDLowSmall (1-10%)Moderate (11-30%)High (Continuing)
7.2Dams and water management/use-NegligibleNegligible (<1%)Serious (31-70%)Moderate (Possibly in the short term, < 10 yrs/3 gen)
8Invasive and other problematic species and genesCDMedium - LowRestricted (11-30%)Moderate - Slight (1-30%)High (Continuing)
8.1Invasive non-native/alien speciesCDMedium - LowRestricted (11-30%)Moderate - Slight (1-30%)High (Continuing)
10Geological events-NegligibleNegligible (<1%)Negligible (<1%)High (Continuing)
10.3Avalanches/landslides-NegligibleNegligible (<1%)Negligible (<1%)High (Continuing)
11Climate change and severe weatherCDMedium - LowPervasive (71-100%)Moderate - Slight (1-30%)High (Continuing)
11.2DroughtsDLowPervasive (71-100%)Slight (1-10%)High (Continuing)
11.4Storms and floodingDLowRestricted - Small (1-30%)Moderate - Slight (1-30%)High (Continuing)

Historical fire regimes and projections for the future under climate change have been examined in detail for the West Kootenays (Utzig et al.. 2011). Over the first half of the 20th century, fires occurred almost annually and burned large areas, especially in the southern part of region, with annual burn exceeding 30,000 ha in some years (Figures 2 and 3 in Utzig et al.. 2011). A threshold appeared to have been reached around 1940 with greatly diminished annual fire frequency until the 1980s, with slight increases thereafter. The decrease was associated with a cooling trend in spring and summer and fire suppression efforts in the latter half of the century. Projected into the future, all models showed increases in the area burned with the greatest increases in the north sub-region. Reflecting uncertainty, there is much variability in the outputs from the different models about the magnitude of the increase in fire frequency, but by 2050 the mean projected increase could be up to 300-fold in the north, 30-fold in the middle, and 15-fold in the south subzone. The projected increases are more modest by 2020, and only in the north exceed historical values recorded since the beginning of the 20th century (Figure 9 in Utzig et al.. 2011).


Biology

Little information is available on the biology of Pygmy Slug, apart from natural history notes in the description of the species (Leonard et al.. 2003) and information associated with subsequent distribution records from Montana and BC (Montana Government 2013; Ovaska and Sopuck, unpubl. data 2007 - 2014). Some general information can be gleaned from the biology of other arionid slugs.

Life cycle and reproduction

Pygmy Slug is hermaphroditic, possessing both female and male reproductive organs (Leonard et al.. 2003). However, like most pulmonate gastropods, individuals probably exchange sperm (Tompa 1984); there is no evidence of self-fertilization in this species.

There is only one observation of egg-laying; a slug from Idaho laid a clutch of three eggs in captivity in July (Leonard et al.. 2003). The oval eggs were large (1 x 1.8 mm versus 9 mm body length of the parent) and hatched seven weeks later in September. In Idaho, adults have been found both in spring and autumn (Leonard et al.. 2003). The Montana Natural Heritage Program database contains 25 records of Pygmy Slug from September to November, with most records from October (Montana Government 2013). In BC, adults (based on body length > 9 mm) and juveniles have been found from September to October (Table 1), but only a few targeted surveys have been conducted at other months. The smallest juveniles were 2 - 3 mm in length and were probably newly hatched.

Juveniles presumably overwinter, but the proportion of adults that do so is unknown. The generation time is probably 1 year or slightly more, based on the small body size of the adults and relatively short life spans of arionid slugs in general.

Physiology and adaptability

Pygmy Slug is often associated with riparian habitats and appears to require a high level of environmental moisture. The degree to which it tolerates habitat disturbance is largely unknown, but it is most likely adversely affected by human activities that alter the hydrology of occupied sites and result in drying or flooding of the forest floor. Due to its small size and resulting ability to exploit moist microhabitats, subpopulations may persist in small remnant habitat patches, provided that moisture requirements are met. However, isolated habitat patches from where the species becomes extirpated are unlikely to be repopulated through immigration, at least over the short term.

Movements and dispersal

Movements and dispersal of Pygmy Slug are unknown. Land snails in general have poor dispersal abilities if not aided by humans or transported by other passive means, such as wind or water (review in Cordeiro 2004). No passive means of transport are known for Pygmy Slug, but it is conceivable that the slugs may inadvertently attach to the fur of mammals such as bears, as speculated for other slugs (COSEWIC 2012).

Interspecific interactions

Leonard et al.. (2003) reported observations of Pygmy Slugs feeding on lichen growing on coarse woody debris on the forest floor. The slugs may also feed extensively on fungi, as reported for other slugs (Prophysaon coeruleum: McGraw et al. 2002), potentially aiding dispersal of their spores. In BC, Pygmy Slugs have been found on fungi growing on downed wood (Ovaska and Sopuck, unpubl. data 2013; Figure 1). Pygmy Slugs probably act as prey for a variety of forest floor invertebrates, such as ground beetles (Coleoptera: Carabidae) and centipedes (Chilopoda). Due to their small size, they are probably not actively hunted by small mammals but may be consumed by birds that forage on the forest floor.


Population sizes and trends

Sampling effort and methods

In BC, survey efforts have focused on elucidating the distribution of Pygmy Slug rather than on obtaining abundance estimates (see Search Effort). Methods have consisted mainly of one or more observers walking through the area of interest and searching the forest floor, concentrating on microhabitats deemed important for gastropods, such as decaying logs, sloughed-off bark, stumps, rocks, or other cover-objects or moist refuges, and accumulations of moist leaf litter. Some of the surveys, including all of those during which Pygmy Slug have been found, included the amount of time spent in intensively searching suitable microhabitat as an index of search effort (Table 1 and references therein).

Abundance

Population sizes and densities are unknown, but the slugs appear to be patchily distributed in the landscape, even within apparently suitable habitats. Most observations in BC have consisted of 1 - 3 slugs per site, but concentrations of 8 - 16 slugs, including juveniles, were found on four occasions (at Sites 2, 8 15, and 34 in Table 1) within an area of approximately 10 - 15 m in diameter. At all sites, the species was usually detected within the first 10-15 minutes of search time or not found at all.

Comparisons of Pygmy Slug records with those of other native forest slugs in the Kootenay region of BC provide some information on their relative rarity. During surveys by Biolinx Environmental Research Ltd in 2007 - 2014, Pale Jumping-slug (Hemphillia camelus) was widespread and abundant when compared to Pygmy Slug; Magnum Mantleslug (Magnipelta mycophaga; COSEWIC status: Special Concern) was more widespread but found only at a few scattered sites; Reticulate Taildropper (Prophysaon andersonii) was found less frequently but has a wide distribution in BC, extending well beyond the Kootenays; Sheathed Slug (Zacoleus idahoensis; COSEWIC 2016) was found only infrequently and in the southern portion of Pygmy Slug’s range.

Fluctuations and trends

Pygmy Slug was discovered only recently (2007), and no information exists of fluctuations or population trends in Canada or the United States.

Rescue effect

The closest Canadian records of Pygmy Slug to the international border with the United States are only 4 km north from eastern Washington State (Site 11 in Table 1 and Figure 3) and 7.6 km north from western Montana (Site 2 in Table 1 and Figure 3). The species has not been documented from Washington, but the habitat south from the BC border appears to be relatively continuous. In western Montana, there are records of the species from within approximately 5 km of the international border (Montana Government 2013). The examination of imagery from Google Earth® shows large clearcuts in the intervening area on the Canadian side, which would impede movements of slugs. However, some interchange of individuals with the United States could occur both through the east and west portions of the Pygmy Slugs’ Canadian range over longer time frames within the constraints of poor dispersal abilities of the slugs and impediments posed by human land uses, such as roads, clearcuts, and settlements.


Threats and limiting factors

Limiting factors

Pygmy Slug exists at the northern limits of its global distribution in southeastern BC, where its distribution most likely reflects post-glacial expansion from refugia farther south. Its northward expansion is probably limited by a short growing season and/or long and cold winters. Drier forest types to the east probably limit its eastward expansion and explain the absence of the species from most of the East Kootenays. Complex topography and the resulting mosaic of drier and wetter habitats probably constrain its distribution both within and among watersheds. Logging has further fragmented habitats and reduced permeability of the landscape to movements and gene flow. Low dispersal ability and requirements for moist habitats limit the speed at which the slugs can colonize new habitats.

Threats

The IUCN threats calculator (Master et al. 2009) was used to assess threats to the Pygmy Slug (Table 3; Appendix 2). Threats were considered across the entire Canadian distribution of the species to account for possible undocumented sites, but using threats and land uses at known sites as guidance. The threats calculator method consists of scoring the scope, severity, and timing for each standard threat category; the overall threat impact is then computed from these ratings.

The overall threat impact for Pygmy Slug was scored as “high - medium”, where the range reflects uncertainty. Under the “high” impact scenario, there were two medium and four low impact threats, whereas under the “medium” impact scenario, there were six low impact threats. The two highest ranking threats, “climate change and severe weather” and “invasive, non-native species”, have much uncertainty associated with both the scope within the next ten years and the severity of the impacts on slug populations. Headings in the following narrative correspond to categories (or subcategories) of the threats calculator, in the approximate order of their perceived importance.

Climate change and severe weather (threat impact medium - low; scope: pervasive; severity: moderate - slight):

Severe weather and increased frequency of extreme events associated with climate change were considered pervasive in scope for Pygmy Slug (71 - 100% populations affected), because the entire Canadian range of the species is likely to be influenced by the same broad weather patterns. However, terrain and habitat features could modulate impacts on the slugs among watersheds and sites. The main impacts on the slugs will probably accrue from droughts and flood events, both of which are predicted to increase in frequency and severity under climate change scenarios (Utzig 2012a). Because of its reliance on habitats with high moisture, prolonged and severe summer droughts may be particularly devastating to local subpopulations of Pygmy Slugs both directly by increasing mortality and indirectly by reducing the length of time available for growth and reproduction. Series of years with droughts that extend well into the autumn are expected to be particularly detrimental. The Kootenay region of British Columbia experienced Stage 2 drought conditions (dry) during May, June and July 2015, followed by Stage 3 conditions (very dry) from August to mid-September (BC Ministry of Forests, Lands and Natural Resource Operations 2015). Four sites where the species had been found in previous years were revisited in late September 2015; Pygmy Slug was found at two of these sites (Ovaska and Sopuck 2015). The drought may have reduced the abundance or detectability of the slugs, but the sample size is too small to draw reliable conclusions. The reduction in detectability was particularly evident at a site on the eastern periphery of the species’ range, where nine Pygmy Slugs were found in 2013 but none in 2015. Whether the slugs were deeper in the substrate or had suffered declines is unknown.

Increased frequency of flooding events could result in mortality or displacement of slugs living close to water courses and could scour riparian areas of the duff layer and refuges. While flooding might be of short duration along mountain streams, its effects are potentially more devastating where the slugs inhabit flatter terrain that may remain inundated for longer periods.

Much uncertainty exists about the severity of the impacts of climate change and severe weather on Pygmy Slug, as reflected by the wide range of assigned threats calculator ratings. However, a precautionary approach is warranted because of the potentially widespread and serious nature of this threat. With a few exceptions, impacts associated with climate change are unstudied for terrestrial gastropods. The studies that do exist have focused on habitat shifts along altitudinal gradients in Europe and have projected range shrinkages and subpopulation declines for high elevation species (Müller et al. 2009) and upward altitudinal shifts for lower elevation species (Baur and Baur 2013). For Pygmy Slug, it is likely that proximate factors such as droughts that drive ecosystem shifts are more important than the shifts themselves; with its low dispersal capability and reliance on moist habitats, the slugs may not be able to track ecosystem shifts that may occur.

Invasive non-native species (threat impact medium - low; scope: restricted; severity: moderate to slight):

Non-native gastropods and other invertebrates pose a threat to native gastropods through competition for food and shelter, predation, and/or alteration of ecosystem processes and habitats. Over 20 species of non-native gastropods have been recorded from BC (Forsyth 2004). Although mostly found in disturbed areas, many are spreading into forested habitats. Humans continue to facilitate the spread of introduced gastropods across the province, where they can be found in most areas frequented by humans, including picnic sites, campsites, and rest stops along highways. Other widely introduced invertebrates in BC include carabid beetles (Coleptera: Carabidae), which can prey on gastropods (Symondson 2004), and earthworms, which can reduce or remove the duff layer through their actions with potentially detrimental effects on native forest floor invertebrates (Addison 2009). In the West Kootenays, introduced gastropods were found at only two of 38 known sites occupied by Pygmy Slug (Sites 1, 10), and were probably also present at at least two additional sites, readily accessed by recreational users (Sites 6, 11). Increased human access to the backcountry associated with resource extraction activities and an expanding road network will facilitate the spread of these and other introduced invertebrates to new areas.

Much uncertainty exists with the severity of impacts of introduced species on Pygmy Slug, as reflected by the wide range of threats calculator ratings. Introduced gastropods pose a threat to native gastropod faunas around the world (Mahtfeld 2000), but their effects in terrestrial habitats are generally poorly documented. An exception is island faunas, where alien invertebrate predators and competitors, including other gastropods, have been largely responsible for the demise of native land snail faunas (e.g., Hawaii: Hadfield et al. 1993; South Pacific: Cowie 2001). In BC, introduced gastropods include scavengers/predators, such as Boettgerilla pallens and Oxychilus species, and herbivores/detrivores, such as species of Arion that can become exceedingly abundant in suitable habitats and could have a demographic advantage over native species in competition for resources. Carabid beetles are known predators of terrestrial gastropods in both natural and disturbed habitats, and slugs form a large portion of the diet of many generalist carabids (Symondson 2004). While snail predators tend to be specialized, predation on slugs does not appear to require specific adaptations by the beetles. In the United Kingdom, carabid beetles with a large proportion of slugs in their diet were relatively large with strong mouth parts and had the ability to forage widely (Tod 1970, cited in Symondson 2004). Defences of slugs against carabid attacks include the production of copious amounts or highly viscous mucus, repellants or toxic chemicals in the mucus or tissues, and tail autotomy (Symondson 2004). Pygmy Slug is not known to possess any of these mechanisms and may rely on crypsis and small size to avoid predation. However, it may be defenceless against aggressive introduced predators, such as the carabid beetle Carabus granulatus, which was observed preying on native slugs (Hemphillia camelus and Prophysaon andersonii) in the West Kootenays during fieldwork for this report; the ability to autotomize the tail appeared to provide no advantage to P. andersonii (Ovaska and Sopuck, unpubl. data 2013). The site where C. granulatus was observed (Site 2013-13 in Appendix 1) is only 2.5 km from a known Pygmy Slug site.

Logging and wood harvesting (threat impact: low; scope: restricted; severity: moderate):

Most of the Canadian distribution of Pygmy Slug is within lands used for forestry. Large areas of the landscape have already been subjected to clear-cut and selective logging, and new logging continues to degrade habitat and fragment the species’ range, but quantitative data on the amount of habitat affected over the next ten years are lacking. Harvesting of maturing second growth has started in the region, also at largely unknown rates. Effects of logging on the slugs would result from changes in moisture and temperature regimes on the forest floor due to canopy removal and from disturbance to the understorey vegetation and forest floor structure.

Based on visual estimation from forestry layers in iMapBC (2014) and Google Earth (2014; imagery from 2003-2013), 95% of the known Pygmy Slug sites are within landscapes with ongoing logging, but it is unknown how many new sites will actually be logged over the next ten years. Only one site (Site 35 in Table 1) is secure from logging. Pygmy Slugs may be able to persist in small forest patches or riparian buffers within logged sites, at least over the short term, as evidenced by their presence in such habitats within recently logged landscapes. However, it is conceivable that there is a time lag before the full effects of recent logging are manifested, and the long-term viability of subpopulations in these habitats is unknown.

Within logged landscapes, Pygmy Slug could receive protection from forested riparian buffers. Riparian buffers are required along larger, fish-bearing streams under the BC Forest and Range Practices Act, but there are no such requirements for small, fishless streams (S6 streams), along which Pygmy Slugs are usually found; nor are there required buffers for other non-classified drainage features, such as seepages. However, some forestry companies operating in the Kootenay region voluntarily leave buffers along all streams, regardless of their size or status (Stuart-Smith pers. comm. 2014). Even with voluntary efforts, many small streams are likely to be impacted, increasing the scope. In addition to riparian buffers, there is usually a 7 m wide no-machinery zone along creeks, although trees may be taken from this zone. Pygmy Slug habitat along creeks in steep-sided gullies would be buffered, because the terrain is usually too steep for timber harvesting (Stuart-Smith pers. comm. 2014).

Fire and fire suppression (threat impact low; scope: small; severity: moderate):

Fires are harmful to terrestrial gastropods by causing direct mortality and, perhaps more importantly, by altering habitat through reduction in shelter and food sources over the short and longer term (Jordan and Hoffman Black 2012). Due to their generally low mobility, gastropods are both unable to escape fire events by moving away and are slow to recolonize burnt areas. In the West Kootenay region, more frequent and severe fires are predicted as climate change proceeds (see Habitat Trends). The size and intensity of the burn are expected to greatly influence the outcome for gastropod populations; greatest effects are likely when the burn covers a large continuous area and extends deep into the ground, while smaller, discontinuous, and less severe burns would be less devastating. In the latter situation, gastropods could survive in underground refugia or unburned habitat patches, which could serve as sources for recolonization once the habitat regenerates. Riparian areas along small creeks inhabited by the slugs may be somewhat protected from fires that sweep the landscape, especially in steep gullies and on north-facing slopes; unburned streamsides within large recent burns were observed at such sites during fieldwork for this report (Ovaska and Sopuck, unpubl. data 2007-2013).

Several studies have reported negative effects of fire on species richness and/or abundance of terrestrial gastropods (review in Jordan and Hoffman Black 2012). Snails seem to be particularly vulnerable (Anderson 2004; Duncan 2005), but effects on slugs have also been reported (Duncan 2005). In southwestern Oregon, both the distribution and abundance of four species of terrestrial gastropods studied were reduced after low-intensity prescribed fires (Duncan 2005). The effects were more severe on snails than on slugs (e.g., Blue-grey Taildropper, Prophysaon coeruleum), but slugs were not found at over a quarter of the sites that supported them during pre-fire surveys. The author suggested that at sites with continued persistence, slugs survived in deep fissures in coarse rock substrate or other underground refuges and suggested that the distribution of microhabitats that allow for vertical movements is important for the long-term viability of slug populations within the landscape.

Roads and railroads (threat impact: low; scope: small; severity: moderate - slight):

Logging roads are prevalent throughout the Pygmy Slug’s range, and a major highway is within 1 km of four known sites (Sites 1, 7, 10 and 34). Visual examination of the landscape within 1 km radius from each known site, based on iMapBC (2014), estimated road density as “high” at six sites (Sites 10, 11, 14, 18, 22, and 32) and low at seven sites (Sites 6, 12, 13, 26, 27, 34 and 35); the remaining 25 sites were rated as “medium” with respect to road density.

New roads associated with forestry and other types of resource extraction are likely to increase over the next ten years with the expansion of these activities to new areas. Adverse effects on slugs from new roads result from habitat loss on the road corridor and through edge effects that can extend far into the forest, from possible changes to drainage patterns, desiccation from increased wind and solar radiation and from habitat fragmentation through barriers to movements. Adverse effects on slugs may also accrue from traffic on existing roads, such as dust that extends into the surrounding forest, or reactivation of roads in previously logged areas. Road corridors may exacerbate effects of droughts through edge effects. However, because resource roads are usually not placed along water courses, their effects on Pygmy Slugs in riparian habitats are limited to stream crossings. Therefore, the scope for this threat was rated as “small” (1 - 10% of slugs affected) and would hover around the lower end of the spectrum (around 1%).

Livestock farming and ranching (threat impact low; scope: small; severity: moderate - slight):

Livestock are usually not free-ranged in dense, steep forested areas characteristic of the West Kootenays, and grazing tenures within the Pygmy Slug’s range occur mostly in drier more open forests in the south and east (iMapBC 2014). However, where free-ranging does occur, cattle and other livestock tend to concentrate in riparian areas, where they can affect slug habitat by compacting soils and removing understorey vegetation. Signs of cattle use were observed at or in the vicinity of 5 (13%) of known sites occupied by Pygmy Slug (Appendix 2).

Cumulative effects

Cumulative impacts result from additive or synergistic interactions among two or more threats, which would elevate the level of the overall threats. For Pygmy Slug, cumulative effects are likely to accrue from interactions among climate change and severe weather, fire and fire suppression, and forestry. Increased frequency and severity of prolonged summer droughts is likely to exacerbate the effects of logging (both recent and planned) and wildfires on the slug’s habitat. For example, narrow forested riparian buffer zones that would otherwise support viable Pygmy Slug subpopulations may no longer do so under prolonged and more frequent droughts. Severe droughts will probably increase the frequency, areal extent, and intensity of wildfires, potentially resulting in the loss of subpopulations from local areas. Both interactions would increase habitat fragmentation and isolation of subpopulations of Pygmy Slugs. Any activities that increase human access, such as resource roads, increase the potential for the introduction or spread of invasive, non-native gastropods and other invertebrates. Climate change and forest disturbance are also expected to facilitate their spread with largely unknown and untracked but potentially serious impacts on native gastropod faunas.

Number of locations

The greatest plausible threats to Pygmy Slug, as per the threats calculator analysis, are from climate change and severe weather and from invasive and introduced species. Considering each occupied watershed as a separate location, where all slugs could be affected by a single threatening event (severe drought), then there are at least 28 locations; the exact number depends on how sub-drainages are delineated and which sites are combined; additional occupied watersheds may exist. Although droughts are likely to be broad-scale across the entire region, impacts on the slugs may be better assessed at watershed scale, depending on amount of logging in the landscape, width of riparian buffers, availability of coarse woody debris, and other site-specific conditions that affect refuges for slugs and moisture regimes on the forest floor. Similarly, effects of introduced invasive species could be considered at the watershed scale, as they may spread through a watershed after an initial introduction.


Protection, status and ranks

Legal protection and status

Currently, Pygmy Slug has no official protection or status under the federal Species at Risk Act, B.C. Wildlife Act, or other legislation.

Non-legal status and ranks

NatureServe (2013) provides the following global, national, and sub-national rankings for Pygmy Slug: Global status - G2 (imperilled); United States - N2 (imperilled); Canada - N1 (critically imperilled); Idaho: S2 (imperilled); Montana - S1S2 (critically imperilled to imperilled; BC - S1? (possibly critically imperilled). In BC, the species is on the provincial red list of species at risk. In Montana, Pygmy Slug is designated as a Species of Concern (Montana Government 2013).

Habitat protection and ownership

Roughly 10% of the Canadian range of Pygmy Slug is within provincial parks, including Valhalla, Kokanee Glacier, West Arm, Lockhart Creek, Kianuko, Stagleap, Champion Lakes, and Kootenay Lake provincial parks (visual estimation from iMapBC protected areas layer). In March 2014, Bill 4, an amendment to the Parks Act was passed by the BC government. The bill allows for exploratory drilling, ore sampling and road building within BC Parks. Approximately 5% of the range is within provincial Wildlife Habitat Areas established for other species, or in other conservation lands (information from iMapBC). Additionally, the Darkwoods Conservation Area, a large (55,000 ha) private property purchased by Nature Conservancy Canada in 2008 located between Nelson and Kootenay lakes and adjacent to West Arm Provincial Park and Midge Creek Wildlife Management Area, is within the core range of Pygmy Slug. This area encompasses 4% of the species’ range, bringing the total percentage of protected lands to 19%. An additional 25% of the range is within community watersheds that receive some degree of protection. Pygmy Slug has not been recorded from any of the above areas with the exception of Site 11, which is within a small conservation area associated with a BC Hydro development. Additionally, Site 35 is within and Site 6 is immediately adjacent to Champion Lakes Provincial Park. Limited surveys within the Darkwoods Conservation Area (Copley, unpubl. data 2010 - 2012) have failed to locate Pygmy Slug.

Much of the range and most records of Pygmy Slug are from provincial forestry lands. As a provincially red-listed species impacted by forest and range practices, Pygmy Slug is potentially eligible for management under the Identified Wildlife Management Strategy of the B.C. Forest and Range Practices Act. However, it is not listed as identified wildlife at present, and hence no specific management measures are available or required. Riparian reserves around fish-bearing streams required under the act may help protect Pygmy Slugs persist in logged areas, but no such protection is required around smaller, non-fish-bearing (S6) streams. Some forest companies voluntarily leave reserve areas around all water courses, including S6 streams (Stuart-Smith pers. comm. 2014).


Acknowledgements and authorities contacted

The report writers contacted the following people in the preparation of this report - we thank all who provided information:

COSEWIC Secretariat:
Neil Jones
Julie Perrault
Sonia Schnobb
Jenny Wu

Canadian Wildlife Service:
Syd Cannings
David Cunnigton
Rhonda Millikin

Parks Canada:
Patrick Nantel

B.C. government representatives:
Ted Antifeau
Dave Fraser
Jennifer Heron

B.C. Conservation Data Centre:
Lea Gelling

Additional contacts:

  • Claudia Copley, Collections manager (arthropods), Royal B.C. Museum, Victoria, B.C.
  • Robert Forsyth, Research Associate, Royal B.C. Museum, Victoria, B.C.
  • Heidi Gardner, Collection Manager (mollusks), Royal British Columbia Museum, Victoria, B.C.
  • Paul Hendricks, Montana Natural Heritage Program
  • William Leonard, Biologist, Olympia, Washington
  • Dwayne Lepitzki, Biologist, Banff, Alberta

Additionally, the following people participated in a threats calculator conference call for the species in February 2014: Ian Adams, Joe Carney, Dave Fraser, Andrew Hebda, Gerry Mackie, Rob McQuarry, Dwayne Lepitzki, Julie Perrault, Kristiina Ovaska, Lennart Sopuck, Kari Stuart-Smith, Charlene Strelaeff. Jenny Wu prepared maps and provided EOO and IAO calculations Funding for the report came from Environment Canada.


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Biographical summary of report writers

Kristiina Ovaska, Ph.D., M.Sc., received her doctoral degree in biology from the University of Victoria, after which she completed two post-doctoral studies in animal behaviour and population biology with McGill University and University of British Columbia, respectively. Presently, she is a partner in Biolinx Environmental Research Ltd., biologist with Habitat Acquisition Trust, and research associate at the Royal British Columbia Museum. Her experience with terrestrial gastropods includes research into effects of forestry practices, studies on patterns of abundance and distribution of species at risk, and numerous surveys in different parts of British Columbia, including the Kootenays. She has prepared status reports, recovery documents, and best management practices guidelines for terrestrial gastropods. Her photographs of gastropods appeared in the Royal B.C. Museum Handbook “Land Snails of British Columbia” by R. Forsyth. She is the author of more than 40 publications in the refereed scientific literature, including several papers on terrestrial gastropods.

Lennart Sopuck, M.Sc., RPBio, has studied a wide variety of wildlife species over the past 30 years. His expertise includes assessing and mitigating effects of various human activities on wildlife, including species at risk. Together with Dr. Ovaska, he is a partner of Biolinx Environmental Research Ltd. and has conducted numerous survey and research projects on terrestrial gastropods of British Columbia. He is co-author of several status reports, recovery strategies, a multi-species action plan, and management documents for terrestrial gastropod species.


Collections examined

Collections at Royal British Columbia Museum were queried, but no specimens were examined.


Appendix 1. Summary of sites surveyed and gastropods found by Biolinx Environmental Research Ltd. (K. Ovaska and L. Sopuck) during fieldwork for this status report in September 2013 and for the Sheathed Slug (Zacoleus idahoensis) in September 2014 in the Kootenay region of British Columbia. additional support for surveys in 2014 came from BC Ministry of Environment. [editorial note: this table has been modified to remove geographic coordinates. the complete table can be obtained by contacting the COSEWIC secretariat.]

Summary of sites surveyed and gastropods found by Biolinx Environmental Research Ltd.
Site IDSite descriptionElev. (m)Habitat typeStand age (yrs)DateSearch effort (person-min)Species found (# of animals)
2013-1Echo Lake Recr. Site, Akolkolex R. FSR, BC859Second-growth coniferous forest8020-Sep-1350Arion rufus (1), Euconulus fulvus (1), Hemphillia camelus (1), Vertigo sp. (1)
2013-2Akolkolex-Dumont FSR, BC600Coniferous old growth forest; moist & rich site20020-Sep-1360Arion sp. (7), Cryptomastix mullani (2), Discus sp. (1), Discus whitneyi (1), Euconulus fulvus (1) Microphysula ingersollii (2), Nesovitrea sp. (1), Vitrina pellucida (3), Zonitoides sp. (1)
2013-3Akolkolex FSR (Site 1), BC646Second-growth mixed-wood forest; along small creek5020-Sep-1360Discus whitneyi (12), Euconulus fulvus (1), Hemphillia camelus (1), Microphysula ingersollii (3), Nesovitrea sp.(2), Punctum randolphii (1), Vertigo sp. (1), Vitrina pellucida (4)
2013-4Akolkolex FSR (Site 2), BC635Second-growth mixed-wood forest; along small creek60-7020-Sep-1360Deroceras laeve (1), Discus sp. (1), Hemphillia camelus (8), Microphysula ingersollii (1)
2013-5Little Fish Creek (near), off HWY 23, S of Revelstoke, BC560Second-growth mixed-wood forest; moist depression30-4020-Sep-1340Allogona ptygophora (1), Discus whitneyi (6), Nesovitrea sp. (3), Zonitoides arboreus (1)
2013-6Eagle Bay Recr. Site, off Shelter Bay FSR, on Arrow Lake, BC451Second-growth coniferous forest; narrow strip of riparian habitat along small creek7020-Sep-1390Prophysaon andersoni (3), Zonitoides arboreus (2)
2013-7Catherine Lake, W side of Upper Arrow Lake, BC833Second-growth mixed-wood forest; along lakeshore40-5021-Sep-1360Allogona ptygophora (9), Euconulus fulvus (3), Hemphillia camelus (6), Zonitoides sp. (3)
2013-8Fosthall/Mosquito Lake FSR, W of Upper Arrow Lake, BC700Older coniferous forest; moist depression10021-Sep-1360None
2013-9Mosquito Lake Recr. Site, W of Upper Arrow Lake, BC682Older mixed-wood forest; narrow remnant strip of forest along lake shore10021-Sep-1340Euconulus pratica, Vertigo sp., Zonitoides sp
2013-10Mosquito Cr. FSR, W of Upper Arrow Lake, BC612Young second-growth mixed-wood forest; along small creek3021-Sep-1360Cryptomastix mullani (2), Hemphillia camelus (9), Microphysula ingersollii (1), Nesovitrea sp.(1), Vertigo sp. (1), Vitrina pellucida (3)
2013-11Steven's Cr. Recr. Site, W of Upper Arrow Lake, BC842Second-growth mixed-wood forest, along fast-flowing creek40-5021-Sep-1360Cryptomastix mullani (4), Euconulus fulvus (1), Hemphillia camelus (1), Nesovitrea sp.(1), Punctum randolphii (5), Vertigo sp. (1)
2013-12Whatshan R. FSR (near east end of Whatshan Lake), BC693Second-growth mixed-wood forest; moist site6021-Sep-1340Cryptomastix mullani (3), Discus whitneyi (4), Euconulus fulvus (2), Hemphillia camelus (1), Nesovitrea sp. (2), Zonitoides sp. (1)
2013-13McDonald Cr. Prov. Park, E side of Arrow Lake, BC456Second-growth mixed-wood forest; Disturbed camping area7021-Sep-13120Allogona ptygophora (1), Arion rufus (2), Cepaea nemoralis (20), Hemphillia camelus (1), Prophysaon andersoni (22)
2013-14Slewiskin (McDonald) FSR (Site 1), S of Nakusp, BC745Older mostly coniferous forest; along fast-flowing tributary stream10022-Sep-1340Discus whitneyi (5), Euconulus fulvus (3), Vertigo sp. (1), Zonitoides sp. (2), Zonitoides arboreus (1)
2013-15Slewiskin (McDonald) FSR (Site 2), S of Nakusp, BC640Second-growth mixed-wood forest; along fast-flowing tributary creek60-7022-Sep-1360Allogona ptygophora (1), Cryptomastix mullani (3), Discus whitneyi (1), Kootenaia burkei (1), Microphysula ingersollii (2), Nesovitrea sp. (1), Planigyra clappi (6), Punctum randolphii (1), Vertigo sp. (8), Vitrina pellucida (3), Zonitoides arboreus (3)
2013-16East Wilson Cr. FSR (Site 1), N of New Denver, BC673Young second-growth mixed-wood forest; along fast-flowing tributary creek4022-Sep-1350Discus whitneyi (20; may include Radiodiscus), Euconulus fulvus (2), Microphysula ingersollii (1), Nesovitrea sp. (3), Punctum randolphii (1), Radiodiscus abietum (1), Vertigo sp. (10), Zonitoides arboreus (1)
2013-17East Wilson Cr. FSR (Site 2), N of New Denver, BC581Second-growth mixed-wood forest; along fast-flowing tributary creek40-5022-Sep-1360Arion sp. (2), Cryptomastix mullani (3), Discus whitneyi (2), Euconulus fulvus (2), Kootenaia burkei (1), Punctum randolphii (5), Vertigo sp. (10), Zoogenetes harpa (10)
2013-18Kane Cr. FSR, E of New Denver, BC829Second-growth mixed-wood forest; along fast-flowing tributary creek70-8022-Sep-1360Arion sp. (3), Euconulus fulvus (1), Hemphillia camelus (2), Nesovitrea sp. (1), Oreohelix sp. (1), Radiodiscus abietum (1),Vertigo sp. (1), Zonitoides arboreus (1)
2013-19Keen Cr. FSR, W of Kaslo, BC758Old-growth coniferous forest; moist area along creek200+22-Sep-1350Discus sp. (1), Euconulus fulvus (3), Pristiloma sp. (1), Vertigo sp. (3), Zonitoides sp. (1)
2013-20Kokanee Cr. Prov. Park, BC558Second-growth mixed-wood forest; Disturbed forest at campsite8022-Sep-1380Arion rufus (3), Cepaea nemoralis (50), Cryptomastix mullani (1), Limax maximus (1)
2013-21Sentinel Mtn FSR, E of Castlegar, BC526Second-growth mixed-wood forest; forest edge at roadside5023-Sep-1350Arion sp. (6), Arion intermedius (10), Cryptomastix mullani (9), Deroceras reticulatum (8), Discus whitneyi (25), Euconulus fulvus (4), Nesovitrea sp.ovitrea sp. (2), Vertigo sp. (1), Vitrina pellucida (7), Zonitoides sp. (1)
2013-22Murphy Cr., S of Castlegar, BC437Young second-growth mixed-wood forest; Disturbed site along creek-side3023-Sep-1340Cryptomastix mullani (4), Nesovitrea sp. (7), Punctum randolphii (1), Zonitoides arboreus (2)
2013-23Casino Cr., SE of Trail, BC1070Second-growth mixed-wood forest; seepage area within dry forest7023-Sep-1360Anguispira kochi (3), Cryptomastix mullani (4), Euconulus fulvus (2), Punctum randolphii (2), Vertigo sp. (5), Zonitoides arboreus (2)
2013-24Seven Mile Road, Pend d'Oreille, BC521Second-growth coniferous forest; Disturbed stream-side forest6023-Sep-1340Allogona ptygophora (4), Deroceras reticulatum (4), Euconulus fulvus (1), Haplotrema vancouverense (2), Microphysula ingersollii (1), Prophysaon andersoni (1), Punctum randolphii (2), Vertigo sp. (2)
2013-259 Mile Cr. (Site 1), Pend d'Oreille, BC703Young second-growth mixed-wood stand; Disturbed stream-side forest3023-Sep-1340Cryptomastix mullani (1), Deroceras laeve (2), Discus whitneyi (2), Euconulus fulvus (1), Oreohelix sp. (1)
2013-269 Mile Cr. (Site 2A), Pend d'Oreille, BC618Older coniferous forest; moist forest along creek10023-Sep-1360Allogona ptygophora (5), Cryptomastix mullani (4), Euconulus fulvus (1), Kootenaia burkei (1), Oreohelix sp (2), Zacoleus idahoensis (2)
2013-27Sheep Cr. FSR (Site 1), S of Salmo, BC1179Older mixed-wood forest; riparian forest along fast-flowing tributary creek100+24-Sep-1350Discus whitneyi (1), Euconulus fulvus (15), Kootenaia burkei (3)
2013-28Sheep Cr. FSR (Site 2), S of Salmo, BC969Second-growth mixed-wood forest; riparian area along fast-flowing creek8024-Sep-1340Discus whitneyi (1), Euconulus fulvus (20), Hemphillia camelus (3), Kootenaia burkei (2), Prophysaon andersoni (2), Vertigo sp. (1), Zonitoides arboreus (3)
2013-29Ezekiel - Corn Cr. FSR, SW of Creston, BC841Second-growth coniferous forest; along fast-flowing creek70-8024-Sep-1340Allogona ptygophora (1), Anguispira kochi (1), Cryptomastix mullani (1), Discus whitneyi (1), Euconulus fulvus (5), Microphysula ingersollii (1)
2013-30Spider-Kid Cr. FSR, E of Creston, BC961Older mixed-wood forest; along fast-flowing creek100+24-Sep-1370Cryptomastix mullani (3), Discus sp. (2), Euconulus fulvus (2), Hemphillia camelus (2), Vertigo sp. (5), Zonitoides sp (1)
2013-31Carroll Cr. Road, W of Yahk, BC993Old-growth coniferous forest; moist area along creek200+24-Sep-1350Kootenaia burkei (1), Zacoleus idahoensis (1)
2013-32Gold Cr. FSR, E of Cranbrook, BC1199Second-growth coniferous forest; moist stream-side in dry landscape8025-Sep-1340Deroceras laeve (1), Discus sp. (1), Euconulus fulvus (2), Vertigo sp. (3), Zonitoides arboreus (1)
2013-33Teepee Cr. FSR, SE of Cranbrook, BC1125Older coniferous forest; moist creek-side10025-Sep-1340Discus whitneyi (1), Euconulus fulvus (1), Kootenaia burkei (9), Vertigo sp. (1)
2013-34Plumbob Cr. FSR, SE of Cranbrook, BC1059Second-growth mixed-wood forest; moist depression and riparian area along slow-moving creek8025-Sep-1340Discus whitneyi (1), Euconulus fulvus (4), Oreohelix sp. (2)
2013-35Caven Cr. FSR, ca. 4 km W of Koocanusa Lake, BC810Second-growth coniferous forest; moist depression in dry landscape8025-Sep-1340Euconulus fulvus (3), Zonitoides arboreus (2)
2014-1AWait Cr/Lost Dog Cr junction ca. 20 km NE from Kimberley, BC867Bottom of ravine in drier forest2016-Sep-14170Euconulus fulvus (10), Microphysula ingersollii (5), Zonitoides arboreus (1)
2014-1BWait Cr/Lost Dog Cr junction ca. 20 km NE from Kimberley, BC849Tributary creek bed on floodplain (dry)1516-Sep-1460Deroceras reticulatum (25), Euconulus fulvus (1), Nesovitrea sp. (3), Zonitoides arboreus (1)
2014-1CWait Cr/Lost Dog Cr junction ca. 20 km NE from Kimberley, BC856Riparian area along creek in ranchland meadowNA15-Sep-1440Deroceras reticulatum (12), Vitrina pellucida (1), Zonitoides nitidus (3)
2014-2AKimberley Nature Park (Site 1), Kimberley, BC1117Riparian area along small, fast-flowing creek in shaded forest7016-Sep-1450I (2), Discus sp. (1), Euconulus fulvus (2), Hemphillia camelus (2), Zonitoides arboreus (2)
2014-2BKimberley Nature Park (Site 2), Kimberley, BC1114Riparian area along small, fast-flowing creek under cottonwoods in shaded forest7016-Sep-1430Arion circumscriptus (1), Discus whitneyi (3), Euconulus fulvus (3), Nesovitrea sp. (6), Vitrina pellucida (1), Zonitoides arboreus (2)
2014-2CKimberley Nature Park (Site C, Elmer Lake), Kimberley, BC1144Riparian area along small creek flowing into Elmer Lake in shaded forest6016-Sep-1430Discus whitneyi (5), Euconulus fulvus (12), Zonitoides arboreus (2)
2014-3Norbury Provincial Park, NE of Cranbrook, BC849Moist pocket of habitat in woodlot in lowland depression5017-Sep-1470Deroceras laeve (3), Discus whitneyi (8), Euconulus fulvus (2), Punctum randolphii (1), Vitrina pellucida (15), Zonitoides nitidus (38)
2014-4Bummers Flats (Site 1), NE of Cranbrook, BC767Forest edge on floodplain of Kootenay R.; patch of aspens (some large) and thicket of shrubs6017-Sep-1450Deroceras laeve (4), Discus whitneyi (2), Euconulus fulvus (1), Euconulus pratica (4), Nesovitrea sp. (1), Zonitoides nitidus (1)
2014-5Rest area on HWY 95A (Lost Dog Creek area), ca. 10 km E of Kimberley, BC892Floodplain of river; dense spruce stands along river; periodic flooding10017-Sep-1460Deroceras laeve (1), Deroceras reticulatum (2), Discus whitneyi (5), Euconulus fulvus (2)
2014-6Meachen Cr. Falls (Site 1), S of St. Mary's Lake, BC1100Ravine along river; lots of windthrow10018-Sep-1460Hemphillia camelus (1), Vertigo sp. (6)
2014-7Meachen Cr. FSR (Site 2), ca 11 km S of St. Mary's Lake, BC1208Steep mossy ravine of fast-flowing tributary creek of Meach Cr.; rocky, substrate along creek100+18-Sep-1450Hemphillia camelus (5), Vertigo sp. (5)
2014-8Meachen Cr. FSR (Site 3 at Fiddler Cr.), ca. 14 S of Mary's Lake, BC1284North-facing sloping side of ravine with young cottonwoods along fast-flowing tributary creek; pockets of deep leaf litter under cottonwoods60-7018-Sep-1440Euconulus fulvus (1), Kootenaia burkei (4), Microphysula ingersollii (1), Vertigo sp. (7)
2014-9Meachen Cr. FSR (Site 4), S of St. Mary's Lake, BC1457Seepage on north slopealign-center text-center18-Sep-1450Hemphillia camelus (8)
2014-10Meachen Cr. FSR (Site 5) S of St. Mary's Lake, BC1567Mid-slope of forest sloping towards river; moist site but not riparian150+18-Sep-1452Hemphillia camelus (2)
2014-11Hellroaring Cr. FSR (Site 1), S. of St. Mary's Lake, BC1304Cottonwood fringe along road in steep mid-slope forest60-7018-Sep-1460Discus whitneyi (3), Kootenaia burkei (1), Microphysula ingersollii (3), Punctum randolphii (1), Vertigo sp. (1), Vitrina pellucida (1)
2014-12Hellroaring Cr. FSR (Site 2), S. of St. Mary's Lake, BC1372Narrow riparian zone along fast-flowing tributary creek through old clearcut; patch of old forest across road along stream (opposite side of road from search area)2018-Sep-1468Euconulus fulvus (2), Hemphillia camelus (9), Magnipelta mycophaga (1), Microphysula ingersollii (2), Punctum randolphii (2), Vertigo sp. (1), Zonitoides sp. (1)
2014-13Gold Cr. FSR (Site 1), ca. 35 km S of Cranbrook, BC1113Flat area along creek-side floodplain with some large spruce100+19-Sep-1440Deroceras laeve (8), Deroceras reticulatum (5), Discus whitneyi (12), Euconulus fulvus (4), Microphysula ingersollii (1), Zonitoides arboreus (2)
2014-14Gold Cr. FSR (Site 2), W of Koocanusa Lake, BC972Well-drained flat area along creek-side7019-Sep-1440Discus whitneyi (1)
2014-15Wickman Cr. FSR (Site 1), off Yahk R. FSR, W of Koocanusa Lake, BC1159Riparian floodplain along creek and upland forest edge (alder fringe)4019-Sep-1450Deroceras laeve (3), Discus whitneyi (8), Euconulus fulvus (1), Microphysula ingersollii (1), Vitrina pellucida (1)
2014-16Wickman Cr. FSR (Site 2), off Yahk R. FSR, W of Koocanusa Lake, BC1184Cottonwood stand along creek in moist depression4019-Sep-1450Discus whitneyi (2), Euconulus fulvus (2), Hemphillia camelus (3), Microphysula ingersollii (3), Vertigo sp. (2), Zonitoides sp. (1)
2014-17ACherry Cr. FSR (Site 1), near Cherry Lake, BC1231Stunted forest on south-facing slope at south end of lake40-5019-Sep-1470Discus whitneyi (2), Zacoleus idahoensis (2), Zonitoides sp. (1)
2014-17BCherry Cr. FSR (Site 2), SW end of Cherry Lake, BC1221Rich alluvial site by stream (inlet/outlet of lake); selectively logged80-9020-Sep-1444Hemphillia camelus (3)
2014-17CCherry Cr. FSR (Site 3), near Cherry Lake, BC1229Alluvial flat by stream, perhaps seasonally flooded; moist site80-9020-Sep-1450Discus whitneyi (3), Euconulus fulvus (2), Kootenaia burkei (2), Nesovitrea sp. (1), Zonitoides arboreus (2)
2014-19Bloom Cr. FSR (Site 1), BC1213Ravine in coniferous forest100+20-Sep-1450Discus whitneyi (4), Euconulus fulvus (1), Hemphillia camelus (1), Zonitoides arboreus (3)
2014-20Bloom Cr. FSR (Site 2), BC1246Riparian zone along fast-flowing tributary creek in otherwise dry forest; north-facing, shaded site50-6020-Sep-1480Euconulus fulvus (1), Hemphillia camelus (11), Microphysula ingersollii (1), Vertigo sp. (2)
2014-21Bloom Cr. FSR (Site 3), BC1269Riparian area along small stream (trickle of water) in second growth forest6020-Sep-1460Discus whitneyi (2), Euconulus fulvus (1), Hemphillia camelus (5), Kootenaia burkei (1), Punctum randolphii (1), Vertigo sp. (1)
2014-22Yahk R FSR (Site 1; near Blacktail Cr.), BC1595Seepage along small creek in spruce forest on north-facing slope120+20-Sep-1470Hemphillia camelus (2), Microphysula ingersollii (3), Punctum randolphii (1), Zacoleus idahoensis (1)
2014-23Gilnockie Cr. (Rec site), off Yahk R FSR, BC1051Riparian floodplain forest by creek8021-Sep-1440Deroceras reticulatum (1), Euconulus fulvus (1), Hemphillia camelus (1), Zonitoides arboreus (1)
2014-24Yahk R FSR (Site 2), BC1105Riparian area by slow-moving tributary creek; mostly clearcut, some selective cutting (with some older trees ca. 70 years old)2021-Sep-1440Allogona ptygophora (2), Oreohelix strigosa (1)
2014-25Yahk R FSR (Site 3), BC1111Moist, periodically flooded alluvial site along fast-slowing larger stream (Yahk River); forest gap with abundant understorey vegetation10021-Sep-1440Allogona ptygophora (4), Euconulus fulvus (2), Kootenaia burkei (1), Magnipelta mycophaga (1), Microphysula ingersollii (1), Oreohelix sp. (1), Zonitoides arboreus (1)
2014-26Yahk R FSR (Site 4), BC1216Riparian forest along small tributary stream60-7021-Sep-1450Discus whitneyi (1)
2014-27Yahk R FSR (Site 5), BC1147Riparian forest along stream; clearcut on other side of stream80-10021-Sep-14110None
2014-28Yahk R FSR (Site 6) at Malpas Cr. FSR, BC1323Older moist coniferous stand with small canopy gaps and depressions with herbaceous vegetation100+21-Sep-1450Euconulus fulvus (1), Hemphillia camelus (2), Microphysula ingersollii (1), Vertigo sp. (1)
2014-29Yahk R FSR (Site 7), BC1627Riparian forest along tributary creek in otherwise dry, pine-dominated forest8021-Sep-1440None
2014-30Yahk R FSR (Site 8), BC1612Patch of trees in ravine60-7021-Sep-1460Zacoleus idahoensis (1)
2014-32Lamb Cr. FSR (Site 1), W of Moyie, BC1121Moist riparian floodplain in narrow ravine (1-sided) within landscape of shelter wood logging; several very large cottonwoods7022-Sep-1440Deroceras laeve (1), Discus whitneyi (12), Euconulus fulvus (1), Kootenaia burkei (1), Microphysula ingersollii (1), Punctum randolphii (1), Vertigo sp. (4)
2014-33Tate Cr. FSR (Site 1),off Lamb Cr. FSR, BC1194Riparian buffer (50-75m wide) in rich floodplain along creek8022-Sep-1440Discus whitneyi (1), Hemphillia camelus (1), Kootenaia burkei (5), Vertigo sp. (1), Vitrina pellucida (1)
2014-34Tate Cr. FSR (Site 2),off Lamb Cr. FSR, BC1392Forested ravine along small creek (riparian zone <20 m) and surrounding upland coniferous forest15022-Sep-1450Euconulus fulvus (2), Hemphillia camelus (2), Kootenaia burkei (2), Microphysula ingersollii (1), Vertigo sp. (3)
2014-35Tate Cr. FSR (Site 3),off Lamb Cr. FSR, BC1384Moist coniferous forest with little understorey except in canopy gaps and old road/trail that traverses site; transitional forest between ICH and ESSF125+22-Sep-1440Euconulus fulvus (1), Hemphillia camelus (1), Microphysula ingersollii (2), Vertigo sp. (1), Zonitoides arboreus (2)
2014-36Irishman R. FSR, near Moyie, BC971Floodplain of creek in pocket of cedars, continuous with older forest along creek60-7022-Sep-1440Discus whitneyi (1), Hemphillia camelus (1), Kootenaia burkei (1)
2014-37Hawkins-Canuck Cr FSR (Site 1), E of Yahk, BC1041Shallow ravine with an intermittent, small creek; moist, north-facing site with abundant hebaceous vegetation7023-Sep-1470Allogona ptygophora (7), Anguispira kochi (6), Discus whitneyi (12), Hemphillia camelus (2), Magnipelta mycophaga (2), Prophysaon andersoni (45), Punctum randolphii (1)
2014-38Hawkins-Canuck Cr FSR (Site 2), E of Yahk, BC1222Shallow ravine with flowing creek and narrow riparian zone50-6023-Sep-1440Discus whitneyi (15), Euconulus fulvus (3), Hemphillia camelus (4), Punctum randolphii (1), Vertigo sp. (4)
2014-39American Cr. FSR, off Hawkins Cr, Meadow Rd, E of Yahk, BC1135Canopy gap with abundant herbaceous growth on sloping terrain in moist forest; seepage area (mostly dry) on site60-7023-Sep-1460Anguispira kochi (60), Discus sp. (20), Oreohelix strigosa (4), Prophysaon andersoni (1), Zacoleus idahoensis (1)
2014-40West Yahk Rd, West of Yahk, BC1150Bottom of gully of small tributary creek (to Hawkins Cr) and surrounding forest100+23-Sep-1480Allogona ptygophora (1), Discus whitneyi (10), Euconulus fulvus (3), Vitrina pellucida (1), Zacoleus idahoensis (4)
2014-41Cold-Freeman FSR (Site 1), off Hawkins FSR, E of Yahk, BC1277Forest edge and ravine along small creek, parallel to road70-8023-Sep-1440Deroceras laeve (3), Hemphillia camelus (2), Microphysula ingersollii (1)
2014-42Cold-Freeman FSR (Site 2), off Hawkins FSR, E of Yahk, BC1179Moist riparian area with hummocks and depressions along creek70-8023-Sep-1440Discus whitneyi (3), Euconulus fulvus (2), Kootenaia burkei (2)
2014-43Goat R FSR (Site 1), NE of Creston, BC849Narrow riparian zone by fast-flowing tributary creek7024-Sep-1440Discus whitneyi (3), Euconulus fulvus (2), Microphysula ingersollii (3), Punctum randolphii (2)
2014-44Skelly Cr FSR (Site 1), off Goat Cr. FSR, NE of Creston, BC944Riparian floodplain along creek60-7024-Sep-1440Discus whitneyi (1), Kootenaia burkei (1), Microphysula ingersollii (2), Punctum randolphii (1), Vertigo sp. (1)
2014-45Skelly Cr FSR (Site 2), off Goat Cr. FSR, NE of Creston, BC1095Narrow (ca 10 m wide) riparian zone along fast-flowing tributary creek, surrounded by dense coniferous forest with little understorey40-5024-Sep-1456Discus sp. (2), Kootenaia burkei (1), Microphysula ingersollii (1), Vertigo sp. (1)
2014-46Goat R FSR (Site 2), NE of Creston, BC1092Moist depression within ca. 50 m from river60-7024-Sep-1440Deroceras laeve (1), Euconulus fulvus (2), Kootenaia burkei (1), Microphysula ingersollii (3), Vertigo sp. (1), Zonitoides arboreus (2)
2014-47Mt. Thompson FSR (Site 1), E of Creston, BC855Moist riparian area along fast-flowing creek in otherwise dry coniferous slope with little understory90-10024-Sep-1454Anguispira kochi (1), Discus whitneyi (5), Euconulus fulvus (1), Kootenaia burkei (1), Punctum randolphii (1)
2014-48Mt. Thompson FSR (Site 2), E of Creston, BC1538Seepage area in ravine/canopy gap150+24-Sep-1440Discus whitneyi (1), Euconulus fulvus (1), Vitrina pellucida (1)
2014-49Sanca Cr FSR (Site 1), N of Creston, BC1189Narrow (ca 10 m wide) riparian zone along fast-flowing tributary creek in otherwise dry, pine-dominated landscape; rare, moist area4025-Sep-1440Hemphillia camelus (1), Kootenaia burkei (5), Microphysula ingersollii (1), Nesovitrea sp. (1), Punctum randolphii (2)
2014-50Sanca Cr FSR (Site 2), N of Creston, BC1339Coniferous slope in older forest; small seepage at site100+25-Sep-1440Discus whitneyi (4), Euconulus fulvus (4), Hemphillia camelus (1), Punctum randolphii (1), Vertigo sp. (1), Zonitoides arboreus (2)
2014-51Sanca Cr FSR (Site 3; South Fork), N of Creston, BC1360Riparian area along small tributary creek in older coniferous forest at valley bottom150+25-Sep-1444Hemphillia camelus (2), Vertigo sp. (1)
2014-52Sanca Cr FSR (Site 4; South Fork), N of Creston, BC1585Moist riparian area on floodplain along stream in older forest; abundant blowdown and big boulders100+25-Sep-1440Euconulus fulvus (2), Kootenaia burkei (1)
2014-53Duck Lake (Site 1), Creston Valley, BC544Cottonwood stand on floodplain along Kootenay River50-6025-Sep-1430Allogona ptygophora (100+), COCLU (1), Deroceras reticulatum (1), Oreohelix strigosa (100+)
2014-55Dodge Cr. FSR (Site 1), S of Creston, BC1052Narrow riparian zone along small, dry tributary creek and surrounding upland forest30-4026-Sep-1446Anguispira kochi (13), Discus whitneyi (1), Hemphillia camelus (2), Oreohelix strigosa (1), Vitrina pellucida (1)
2014-56Dodge Cr. FSR (Site 2) at Dodge Cr, S of Creston, BC1325Riparian zone in young forest at headwaters of Dodge Cr; landscape is otherwise dry with clearcutting and only a few creeks30-4026-Sep-1480Anguispira kochi (4), Discus sp. (3), Euconulus fulvus (3), Hemphillia camelus (7), Kootenaia burkei (1), Microphysula ingersollii (1), Punctum randolphii (1), Vertigo sp. (50), Vitrina pellucida (1)
2014-57Blazed Cr/Jersy Cr FSR off HWY 3, W of Creston, BC1102Older coniferous forest along fast-flowing creek100+26-Sep-1444Anguispira kochi (3), Cryptomastix mullani (1), Discus whitneyi (2), Hemphillia camelus (1), Nesovitrea sp. (1), Oreohelix sp. (1), Zonitoides arboreus (1)
2014-58Maryland FSR (Site 1) off HWY 3, W of Creston, BC1508Subalpine open forest; very moist100+26-Sep-1454Hemphillia camelus (2), Pristiloma chersinella (1)
2014-59BBoundary Lake off Boundary L. FSR, W of Creston, BC1288Moist old growth forest with seepages close to lakeshore150+26-Sep-1450Deroceras laeve (1), Discus whitneyi (1), Hemphillia camelus (1), Pristiloma chersinella (1)
2014-59CBoundary Lake, W of Creston, BC1288Moist old growth forest with seepages close to lakeshore150+26-Sep-14130Hemphillia camelus (2)
2014-60Maryland Cr FSR, W of Boundary L, BC1300Moist coniferous old growth stand by stream125+27-Sep-1440Discus whitneyi (1), Hemphillia camelus (2), Vertigo sp. (1)
2014-61Monk Cr FSR, W of Creston, BC1411Moist old coniferous forest with productive deep soil in swale100+27-Sep-1460Discus whitneyi (5), Kootenaia burkei (2), Magnipelta mycophaga (1), Pristiloma chersinella (5), Punctum randolphii (2)
2014-62Stagleap Provincial Park (from Monk Cr FSR Entrance), Kootenay Pass, BC1960High elevation old growth forest, very moist150+27-Sep-1458Hemphillia camelus (1), Vitrina pellucida (1)
2014-64Rosebud Lake Rd. S of Salmo, BC810Shrubby riparian zone along small creek in ravine within mostly young, logged landscape2027-Sep-1448Allogona ptygophora (1), Arion circumscriptus (1), Arion rufus (2) Cochlicopa lubrica (1), Deroceras laeve (2), Discus whitneyi (8), Euconulus fulvus (1), Vertigo sp. (1), Zonitoides sp. (3)
2014-65HWY 6 to Nelway (small spur), S of Salmo, BC668Moist riparian area along stream40-6027-Sep-14126Discus whitneyi (1), Haplotrema vancouverense (1), Kootenaia burkei (8), Nesovitrea sp. (2)
2014-66AChampion Lakes (Site 1), N of Trail, BC1072Moist old forest with small creek120+28-Sep-14140Anguispira kochi (3), Cryptomastix mullani (5), Discus whitneyi (10), Euconulus fulvus (4), Nesovitrea sp. (1), Punctum randolphii (2), Zonitoides arboreus (1)
2014-66BChampion Lakes (Site 2), N of Trail, BC1079Old forest with abundant well-decayed moist wood100+28-Sep-1440Discus whitneyi (1), Kootenaia burkei (1)
2014-67Nine Mile Rd, S of Fruitvale, BC850Disturbed forest in moist depression40-5028-Sep-1450Cryptomastix mullani (2), Discus whitneyi (10), Euconulus fulvus (6), Hemphillia camelus (2), Nesovitrea sp. (1), Oreohelix strigosa (18), Prophysaon andersoni (12), Zonitoides arboreus (1)
2014-68Bear Cr FSR, N of Fruitvale, BC724Moist disturbed site in ravine with small creek within landscape of drier forest40-5028-Sep-1440Anguispira kochi (16), Cryptomastix mullani (3), Discus whitneyi (16), Hemphillia camelus (1), Nesovitrea sp. (1), Zonitoides arboreus (1)
2014-69Bear Cr FSR (Site 2), N of Fruitvale, BC821Ravine with small creek at bottom in patch of second-growth coniferous forest50-6028-Sep-1440Deroceras laeve (1), Discus whitneyi (2), Euconulus fulvus (4), Zonitoides arboreus (1)
2014-70King George VI Prov Park, off HWY 22, S of Rossland, BC693Moist forest edge by dried up creek8028-Sep-1440Allogona ptygophora (3), Arion circumscriptus (30), Cryptomastix mullani (2), Euconulus fulvus (10), Oreohelix strigosa (1), Prophysaon andersoni (23), Zonitoides arboreus (1)
2014-71Archibald - Tillicum FSR (Site 1), SW of Salmo, BC879Moist shady forest with big old stumps in depression along creek7029-Sep-1470Discus whitneyi (3), Haplotrema vancouverense (1), Hemphillia camelus (1)
2014-72Archibald - Tillicum FSR (Site 2), SW of Salmo, BC1229Moist riparian zone along small creek within logged landscape50-6029-Sep-1450Euconulus fulvus (3), Hemphillia camelus (2), Kootenaia burkei (5), Microphysula ingersollii (2), Vertigo sp. (10)
2014-73Erie Cr FSR (Site 1), N of Erie, NW of Salmo, BC991Moist ravine along small creek within landscape of dry, younger (logged) forest60-7029-Sep-1440Discus whitneyi (2), Euconulus fulvus (2), Kootenaia burkei (2), Nesovitrea sp. (3), Punctum randolphii (2), Zonitoides arboreus (1)
2014-74Erie Cr FSR (Site 2), N of Erie, NW of Salmo, BC915Moist riparian floodplain forest100+29-Sep-1440Hemphillia camelus (3), Kootenaia burkei (1)

Appendix 2. Threats calculator results, with notes, for Pygmy Slug based on conference call in May 2014.

Threats assessment worksheet

Species or Ecosystem Scientific Name:
Kootenaia burkei
Date:
2/5/2014
Assessor(s):
Ian Adams, Joe Carney, Dave Fraser, Andrew Hebda, Gerry Mackie, Rob McQuarry, Dwayne Lepitzki, Julie Perrault, Kristiina Ovaska, Lennart Sopuck, Kari Stuart-Smith, (revision of initial assessment by Ovaska and Sopuck based on comments)
References:
Draft COSEWIC status report
Overall reat Impact Calculation Help:
Threat ImpactThreat Impact (descriptions)Level 1 Threat Impact Counts:
high range
Level 1 Threat Impact Counts:
low range
AVery High00
BHigh00
CMedium20
DLow46
-Calculated Overall Threat Impact:HighMedium
Threats Assessment Worksheet Table.
#ThreatImpact
(calculated
Impact
(description)
Scope
(next
10 Yrs)
Severity
(10 Yrs
or
3 Gen.)
TimingComments
1Residential and commercial development-NegligibleNegligible (<1%)Extreme (71-100%)High (Continuing)-
1.1Housing and urban areas-NegligibleNegligible (<1%)Extreme (71-100%)High (Continuing)1 site (7% of 15) near town that might expand; over the entire range, residential development probably minimal in slug habitats, although river valleys may be targeted.
1.2Commercial and industrial areas-NegligibleNegligible (<1%)Extreme (71-100%)High (Continuing)2 sites (13%) affected; may be expansion in Roseberry area or infrastructure associated with Pend d'Oreille dam
1.3Tourism and recreation areas-NegligibleNegligible (<1%)Serious (31-70%)Moderate (Possibly in the short term, < 10 yrs/3 gen)No plans for new developments known
2Agriculture and aquacultureDLowSmall (1-10%)Moderate - Slight (1-30%)High (Continuing)-
2.1Annual and perennial non-timber crops-NegligibleNegligible (<1%)Serious (31-70%)High (Continuing)No specific examples known in slug habitat, but expansion of hay fields could occur; slug habitat in areas of productive soils
2.2Wood and pulp plantations------
2.3Livestock farming and ranchingDLowSmall (1-10%)Moderate - Slight (1-30%)High (Continuing)Ranching mostly in drier areas of West Kootenays; cattle tend to concentrate in riparian areas; affect understory plants and riparian areas by compacting soils and removing vegetation; some cattle in Hawkins Creek area, but no free-range cattle in most areas within the species' range. Few tenures for grazing within the slug's range, mostly in SE part of range.
2.4Marine and freshwater aquaculture------
3Energy production and mining-NegligibleNegligible (<1%)Extreme - Serious (31-100%)Moderate (Possibly in the short term, < 10 yrs/3 gen)-
3.1Oil and gas drilling-----No oil and gas drilling or extraction within the slug's range at present
3.2Mining and quarrying-NegligibleNegligible (<1%)Extreme - Serious (31-100%)Moderate (Possibly in the short term, < 10 yrs/3 gen)Sub-surface mining grants in the immediate vicinity of 3 sites (20% of 15 sites), but their developed probability within next 10 years is low; lots of exploration but likelihood of new operating mines is low. Historically, lots of mining exploration, but looking into the future, scope is probably <1%
3.3Renewable energy-----Possible on some of some ridges, but no examples known.
4Transportation and service corridorsDLowSmall (1-10%)Moderate - Slight (1-30%)High (Continuing)-
4.1Roads and railroadsDLowSmall (1-10%)Moderate - Slight (1-30%)High (Continuing)All sites are near (within 1 km) roads, and roads are expanding to new areas with resource extraction. Effects on slugs are from habitat loss (corridor & through edge effects), possible changes to drainage patterns, and habitat fragmentation (barriers to movements) associated with new roads, and habitat degradation from traffic on existing roads (e.g., dust). New resource roads are seldom (if ever) built along creeks but will cross them - therefore amount of slug habitat that is lost is small. Scope hovers around the low end (around 1%) and could be negligible.
4.2Utility and service lines-NegligibleNegligible (<1%)Moderate (11-30%)High (Continuing)Power transmission lines present at 4 sites (27% of 15 sites). Effects are from land clearing associated with the expansion of existing lines or construction of new lines; likelihood of new lines (apart from minor ones to individual houses) is small. Maintenance activities such as brushing are not a threat because habitat has already been lost. Severity higher than for roads because of larger footprint & edge effects.
4.3Shipping lanes------
4.4Flight paths------
5Biological resource useDLowRestricted (11-30%)Moderate (11-30%)High (Continuing)-
5.1Hunting and collecting terrestrial animals------
5.2Gathering terrestrial plants-NegligibleRestricted - Small (1-30%)Negligible (<1%)High (Continuing)Mushroom picking; mostly in recent burns but also in forest; some sites are near known mushroom picking areas.
5.3Logging and wood harvestingDLowRestricted (11-30%)Moderate (11-30%)High (Continuing)Logging (clearcut, selective cut) is present within 1 km of records at all sites; some is old (from 1960s - 1980s), but second growth harvesting occurring at least at some sites; difficult to get information on trends for next 10 years. Riparian leave strips mitigate effects to some degree, if left on small creeks that slugs occupy. Forestry buffers are not required in small creeks with no fish (S6 streams), but some forestry companies voluntarily leave buffers along them (Kari Stuart Smith pers. comm. 2013). Despite of voluntary efforts, many small streams are likely to be impacted, increasing the scope. There is usually also a 7 m wide no-machinery zone along creeks, but trees may be taken from this zone. Non-classified drainages (such as seepages) don't need to be buffered. Gullies would be buffered because the terrain is usually too steep for harvesting. Scope elevated from Small - Restricted to Restricted in response to review comments (on 24 Jun-14), reflecting lack of requirements for buffers for small streams and seepages.
5.4Fishing and harvesting aquatic resources------
6Human intrusions and disturbance-NegligibleRestricted (11-30%)Negligible (<1%)High (Continuing)-
6.1Recreational activities-NegligibleRestricted (11-30%)Negligible (<1%)High (Continuing)Recreation affects 6 known sites (40% of 15 sites), based on proximity to trailheads & other recreational opportunities; scope lowered much of overall is away from well travelled areas (e.g., big mountaneous parks). Impacts are from ATV use & snowmobiling (soil compaction & damage to vegetation); hiking on trails has little or no impact.
6.2War, civil unrest and military exercises------
6.3Work and other activities------
7Natural system modificationsDLowSmall (1-10%)Moderate (11-30%)High (Continuing)-
7.1Fire and fire suppressionDLowSmall (1-10%)Moderate (11-30%)High (Continuing)ICH is relatively wet zone, and stand-replacing events are rare. Fires may occur in drier areas of the zone. Fires tend to be more severe when they do happen, due to fire suppression and climate change. Fires seem to be getting hotter and more severe in the area. Fire retardants using in fighting fires can also be detrimental to slugs, but no data are available.
7.2Dams and water management/use-NegligibleNegligible (<1%)Serious (31-70%)Moderate (Possibly in the short term, < 10 yrs/3 gen)One known site is by a hydro-electric dam, which could potentially be expanded or changing water levels could affect this site. Run-of-river projects could affect the slugs, but no plans found in iMap within the slug's range (note: iMap data not complete; several are approved or proposed within the slugs' range, as per revised draft report)
7.3Other ecosystem modifications-UnknownUnknown--Silviculture systems modifying forest compositions, e.g., predominant planting Douglas-fir
8Invasive and other problematic species and genesCDMedium - LowRestricted (11-30%)Moderate - Slight (1-30%)High (Continuing)-
8.1Invasive non-native/alien speciesCDMedium - LowRestricted (11-30%)Moderate - Slight (1-30%)High (Continuing)Introduced gastropods are present or potentially present at 4 occupied sites (27% of 15 sites); other introduced macro-invertebrates, including predators, such as ground beetles, may also be present at these sites. The introduced carabid bettle Carabus granulatus has been observed preying on native slugs in the West Kootenays only a couple km away from known Pygmy Slug site (Ovaska and Sopuck, unpubl. data 2013). Much uncertainty exists with impacts of introduced species.
8.2Problematic native species------
8.3Introduced genetic material------
9Pollution------
9.1Household sewage and urban waste water------
9.2Industrial and military effluents------
9.3Agricultural and forestry effluents-UnknownUnknownUnknown-Fuel spill associated with fighting a forest fire 2 km downstream of the Lemon Creek site (Site 4) on 26 July 2013. Pesticides & herbicides generally not used in forestry in the area. Fertilizers: occasionally applied to planted areas but not a common practice.
9.4Garbage and solid waste------
9.5Air-borne pollutants-Unknown----
9.6Excess energy------
10Geological events-NegligibleNegligible (<1%)Negligible (<1%)High (Continuing)-
10.1Volcanoes------
10.2Earthquakes/ tsunamis------
10.3Avalanches/landslides-NegligibleNegligible (<1%)Negligible (<1%)High (Continuing)Example: large landslide at Johnsons Landing by Kootenay Lake, just northeast of the known range of the species in 2012
11Climate change and severe weatherCDMedium - LowPervasive (71-100%)Moderate - Slight (1-30%)High (Continuing)-
11.1Habitat shifting and alteration-----ICH will expand with climate warming but the slugs may not be able to take advantage of new areas due to pace of change.
11.2DroughtsDLowPervasive (71-100%)Slight (1-10%)High (Continuing)Probably main issue for slugs. More prolonged and severe summer droughts are predicted. Much uncertainty with both scope and severity. Although climate patterns and droughts would be region-wide, slugs in different parts of the range may be affected differently because of differences in moisture regimes due to hydrology and terrain and availability of refuges. Consider effects at watershed scale.
11.3Temperature extremes-----At the northern limits of distribution in BC; probably not an issue
11.4Storms and floodingDLowRestricted - Small (1-30%)Moderate - Slight (1-30%)High (Continuing)Flooding is an issue because of the affinity of the slugs to riparian habitats. However, slugs may have some capability of surviving floods, which are a natural seasonal event. Spring freshets may be more intense in the future, although probably of short duration, and may displace slugs. At sites on flatter terrain, flooding could result in extirpation of local populations.

Glossary

Impact
The degree to which a species is observed, inferred, or suspected to be directly or indirectly threatened in the area of interest. The impact of each threat is based on Severity and Scope rating and considers only present and future threats. Threat impact reflects a reduction of a species population or decline/degradation of the area of an ecosystem. The median rate of population reduction or area decline for each combination of scope and severity corresponds to the following classes of threat impact: Very High (75% declines), High (40%), Medium (15%), and Low (3%). Unknown: used when impact cannot be determined (e.g., if values for either scope or severity are unknown); Not Calculated: impact not calculated as threat is outside the assessment timeframe (e.g., timing is insignificant/negligible or low as threat is only considered to be in the past); Negligible: when scope or severity is negligible; Not a Threat: when severity is scored as neutral or potential benefit.
Scope
Proportion of the species that can reasonably be expected to be affected by the threat within 10 years. Usually measured as a proportion of the species' population in the area of interest. (Pervasive = 71-100%; Large = 31-70%; Restricted = 11-30%; Small = 1-10%; Negligible < 1%).
Severity
Within the scope, the level of damage to the species from the threat that can reasonably be expected to be affected by the threat within a 10-year or three-generation timeframe. Usually measured as the degree of reduction of the species' population. (Extreme = 71-100%; Serious = 31-70%; Moderate = 11-30%; Slight = 1-10%; Negligible < 1%; Neutral or Potential Benefit > 0%).
Timing
High = continuing; Moderate = only in the future (could happen in the short term [< 10 years or 3 generations]) or now suspended (could come back in the short term); Low = only in the future (could happen in the long term) or now suspended (could come back in the long term); Insignificant/Negligible = only in the past and unlikely to return, or no direct effect but limiting.