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BC Conservation Data Centre: Conservation Status Report

Plestiodon skiltonianus
Western Skink



 
Scientific Name: Plestiodon skiltonianus
Scientific Name Synonyms: Eumeces skiltonianus
English Name: Western Skink
   
Provincial Status Summary
Status: S3S4
Date Status Assigned: March 30, 2018
Date Last Reviewed: March 30, 2018
Reasons: Western Skink has a restricted range, a low number of occurrences and threatened habitat. The greatest threats include habitat loss due to residential, commercial, and agricultural development.
 
Range
Range Extent: F = 20,000-200,000 square km
Range Extent Estimate (km2): 37,665
Range Extent Comments: In 2014, COSEWIC calculated the extent of occurrence (EO) of Western Skinks in B.C. to be 25,086 km2, using the minimum convex polygon method with localities confirmed since 2000. If all records, including those before 2000, are used, then the EO is 37,665 km2. This is much larger than the calculation used in the previous rank assessment (<2,000km2, COSEWIC 2002) as the calcuation likey excluded unsuitable habitat (COSEWIC 2014i).

2012:Skinks are found across southern BC, except the southwestern portion, Vancouver Island or the Gulf Islands. Ovaska and Englestoft (2002) estimate a range of less than 2000km squared. For assessment purposes the maximum estimate includes Kamloops and Princeton records (4500km squared) whereas minimum estimate (2500km squared) does not include these older northern and western records (Dupuis 2002).
Area of Occupancy (km2): FG = 126-2,500
Area of Occupancy Estimate (km2): 100
Area of Occupancy Comments: From COSEWIC 2014i: "The index of area of occupancy (IAO) for Western Skinks is 248 km² (62 2x2 km grid cells), based on occurrence records since 2000, and 400 km², if all records, including those before 2000, are included."

2012: Occupancy is restricted by the availability of hibernacula (talus slopes and deep fissured rock outcrops) in proximity to slopes of southern exposure. The species probably occupies about 10% of its range (Dupuis 2002). Ovaska and Englestoft (2002) estimate a range of occupancy of less than 200km squared.
 
Occurrences & Population
Number of Occurrences: C = 21 - 80
Comments: Increased survey efforts have resulted in the finding of Western Skinks at new and previously known localities throughout much of the species? Canadian range in British Columbia (COSEWIC 2014i). Currently there are 40 occurrences mapped by the Conservation Data Centre; however, that is likely an underestimate as updates have not been made since 2011 (L.Gelling, pers. comm. 2017).
Number of Occurrences with Good Viability / Ecological Integrity: U = Unknown
Percent Area with Good Viability / Ecological Integrity: U = Unknown
Number of Occurrences Appropriately Protected & Managed: U = Unknown
Comments: "Several occupied sites are protected within the Vaseux-Bighorn National Wildlife Area, Vaseux Protected Area, Okanagan Mountain Provincial Park, Skaha Bluffs Park, Haynes Lease Ecological Reserve, Anarchist Protected Area, Pilot Bay Park, Kootenay Lake Park, Midge Creek Wildlife Management Area, Creston Valley Wildlife Management Area, Fort Shepherd, and private conservation lands owned by The Nature Trust of BC and The Nature Conservancy of Canada.Unknown how many may be adequately protected." (B.C. Western Skink Working Group. 2013). The vast majority of the habitats within this species range are privately owned, however some occurrences are protected in the Okanagan Mountain (10,000 ha) and Vaseaux Lake (32 ha) parks (COSEWIC 2002j).
Population Size: U = Unknown
Comments: There have been no studies of population size or trends in this species (COSEWIC 2014i).
 
Threats (to population, occurrences, or area affected)
Degree of Threat: C = Medium
Comments: From COSEWIC 2014i: "The most significant threats are from continued habitat loss due to residential, commercial, and agricultural development. Many skink populations occur on private lands, where development pressure can be intense (B.C. Western Skink Working Group 2013). In addition to having a direct impact on skink populations, these threats may reduce genetic variability, increasing extirpation risk and limiting the ability to adapt to changing environments (Delaney et al. 2013)."

2012: The main threat is from loss of habitat via urban and agricultural development and possibly from recreational development. Often this loss is irreversible (road construction and housing projects) and the skinks ability to disperse through fragmented landscapes is unknown but unlikely to be high given the clustered nature of its distribution. Overgrazing by cattle, together with associated invasions of introduced weeds, also pose threats to both woodland and grassland habitats in south-central British Columbia (Pitt and Hooper 1994). In recent years, wooded areas have increasingly been used for cattle grazing. Grazing may adversely affect herbaceous cover in forest openings used by E. skiltonianus (Ovaska and Englestoft 2002).
It is, however, relatively tolerant of human presence (Dupuis 2002). Feral cats have also been cited as has quarrying of the rock cliffs (O. Dyer, pers. comm.). There also is the possibility of threats by the pet trade (Ovaska and Englestoft 2002).
 
Trend (in population, range, area occupied, and/or condition of occurrences)
Short-Term Trend: U = Unknown
Comments: "There have been no studies of population size or trends in this species. Quality of habitat continues to decline in areas with human population growth." (COSEWIC 2014i)
Long-Term Trend: U = Unknown
 
Other Factors
Intrinsic Vulnerability: B=Moderately vulnerable
Comments: Two to six eggs are laid annually, the female guards and warms them until they hatch (Matsuda et al. 2006).
Environmental Specificity: BC=Narrow to moderate.
Comments: Preferences are for areas with lots of cover and debris, i.e. leaf litter, logs, bark or rocks. They use talus slopes for hibernacula.
Other Rank Considerations:
 
Information Gaps
Research Needs: Characterizations of preferred habitat and determination of ability to disperse.
Inventory Needs: There is potential that with continued surveys throughout the appropriate habitat, that the skink may be found to be more common than records indicate. Distribution within the range also needs to be determined.
 
Stewardship
Protection:
Management:
 
Version
Author: Dupuis, L., L. Ramsay and L. Gelling
Date: March 30, 2018
 
References

COSEWIC. 2014i. COSEWIC status appraisal summary on the Western Skink Plestiodon skiltonianus in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. xvi pp. 

B.C. Western Skink Working Group. 2013. Management Plan for the Western Skink (Plestiodon skiltonianus) in British Columbia. Prepared for the B.C. Ministry of Environment, Victoria, BC. 28 pp.
BC Conservation Data Centre: Conservation Data Centre Mapping Service [web application]. 2006. Victoria, British Columbia, Canada. Available: http://maps.gov.bc.ca/imf50/imf.jsp?site=cdc.
COSEWIC. 2002j. COSEWIC assessment and status report on the western skink Eumeces skiltonianus in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vi + 19 pp.
Dulisse, J. 2004. Columbia basin western skink inventory and assessment: 2004 survey results. Columbia Basin Fish & Wildlife Compensation Program, Nelson.
Dulisse, J. 2006. Columbia basin western skink inventory and assessment: 2005 results. Columbia Basin Fish & Wildlife Compensation Program, Nelson.
Dupuis, L. 2002. NatureServe ranking form for Eumeces skiltonianus. Prepared for B.C. Minist. Sustainable Resour. Manage., Conservation Data Centre, Victoria, BC.
GBIF.org. 2025e. GBIF. Occurrence download for Plestiodon skiltonianus. Accessed 8 January 2025.
Gregory, P.T. and R.W. Campbell. 1984. Royal British Columbia Museum Handbook: the reptiles of British Columbia. Royal British Columbia Museum, Victoria. 102 pp.
Ovaska, K.E. and C. Engelstoft. 2002. COSEWIC status report on the western skink Eumeces skiltonianus in Canada, in COSEWIC assessment and status report on the western skink Eumeces skiltonianus in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. 1-19 pp.
 

Please visit the website Conservation Status Ranks for information on how the CDC determines conservation status ranks. For global conservation status reports and ranks, please visit the NatureServe website http://www.natureserve.org/.

Suggested Citation:

B.C. Conservation Data Centre. 2018. Conservation Status Report: Plestiodon skiltonianus. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Jul 2, 2025).