BC Conservation Data Centre: Conservation Status Report
Ovis dalli stonei
Stone's Sheep
| Scientific Name: | Ovis dalli stonei |
|---|---|
| English Name: | Stone's Sheep |
| Provincial Status Summary | |
| Status: | S3S4 |
| Date Status Assigned: | March 21, 2017 |
| Date Last Reviewed: | March 21, 2017 |
| Reasons: | Populations have remained relatively stable since 1990 throughout much of the range, however declines have been noted in some areas of the Province, particularly in the Muskwa-Kechika Management Area (M-KMA) where Stone?s sheep (Ovis dalli stonei) population has declined significantly. (Bill Jex, pers. comm. 2017). The threat assessment identified climate change related factors such as icing and increased heavy snowfall events as risks. Fire suppression and reduction of wildfire may have lead to invasion of grassy meadow habitat by deciduous cover, reducing forage value and habitat quality). Recent transmission of disease to wild sheep from domestic goats and sheep has increased the risk of significant loss of thinhorn sheep metapopulations (Jex et al. 2016). Recent research indicating Stone's sheep range is entirely within BC changes the responsibility (former species range included the Yukon and Northwest Territories). (Sim et al. 2016) |
| Range | |
| Range Extent: | F = 20,000-200,000 square km |
| Range Extent Estimate (km2): | 42000 |
| Range Extent Comments: |
GIS calculation of occupied suitable habitat for Stone's sheep in BC (Bill Jex, pers. comm.). Stone?s sheep are distributed along the interior side of the Coast Range from the Yukon border to the vicinity of Mount Edziza and Spatsizi parks in the Stikine drainage and eastward into the Cassiar, Omineca, Muskwa, and northern Rocky Mountain ranges to about 80km northwest of Chetwynd. The Pine River valley is the approximate dividing line between Stone?s sheep and Bighorn Sheep in British Columbia (BC CDC 2013). Many southern populations are isolated. Recent research suggests clear south and north clades of Dall's and Stone's sheep between northern B.C. and the Yukon, with Dall?s sheep and intergrades (Fannin sheep) closely related in the Yukon and extreme northwest B.C., and Stone?s sheep in the south and east of B.C. (Sim et al. 2016) |
| Area of Occupancy (km2): | H = 2,501-12,500 |
| Linear Distance of Occupancy: | U = Unknown |
| Area of Occupancy Comments: | Stone's sheep in BC occupy northern Mountain ranges and plateaus in BC: Interior Plateau and Mountains (Cassiar Mountains - Fannin and Stone's, Omineca Mountains, Stikine Plateau, Skeena Mountains); North and Central Canadian Rocky Mountains; Kaska Mountains; and Coast Mountains - Fannin and Stone's sheep. (Jex et al. 2016). |
| Occurrences & Population | |
| Number of Occurrences: | C = 21 - 80 |
| Comments: | List via |
| Number of Occurrences with Good Viability / Ecological Integrity: | Rank Factor not assessed |
| Percent Area with Good Viability / Ecological Integrity: | F = Excellent (>40%) |
| Number of Occurrences Appropriately Protected & Managed: | C = 4 - 12 |
| Comments: | Stone's sheep in BC occur within numerous protected areas ranging from Class A Provincial Parks to current and proposed Ungulate Winter Ranges (Bill Jex, pers. comm. 2016) |
| Population Size: | F = 10,000 - 100,000 individuals |
| Comments: | The population estimate of 10,000-16,000 in 2016 is based on 2014-2015 surveys (Bill Jex, pers. comm. 2017). The overall population of Stone's sheep was estimated to be 11,500 in 1990. |
| Threats (to population, occurrences, or area affected) | |
| Degree of Threat: | B = High |
| Comments: |
In the past, overharvesting and human activities (mining, forestry, etc.) affected Stone's sheep, but the annual local harvest is closely monitored and restricted to full-curl rams in British Columbia, and is not a conservation concern (Bill Jex, pers. comm.). An effective environmental assessment and mitigation process related to natural resource development can reduce development impacts. R. Marshall (pers. comm.) believes increased access and the resulting increased disturbance, as well as unregulated First Nations harvest are of potential concern. Current threat assessment increases risk to high as a result of: recent localized metapopulation declines and declines in adjacent jurisdictions (Bill Jex, pers. comm. 2017; Troy Hegel, pers. comm. 2016).; Climate change implications that result in increased frequency of icing events (making winter range forage inaccessible) and heavy snowfall events (Troy Hegel, pers. comm. 2016; Bill Jex, pers. comm. 2017); and catastrophic population collapse from exposure to disease transferred from domestic sheep and goats in proximity to wild sheep.Cross-valley migrations of Stone's sheep in Cassiar Mountains, brings wild sheep in close proximity to formerly ranged domestic goats (Schwantje 2016). Wild sheep are susceptible to a variety of diseases that affect herd viability. The most important diseases affecting wild sheep populations are respiratory infections that result in pneumonia. Bacteria of the family Pasteurellaceae (Pasteurella multocida, Mannheimia haemolytica and Bibersteinia trehalosi), and Mycoplasma ovipneumoniae are the most frequently isolated respiratory pathogens from wild sheep with pneumonia. Pneumonia caused by these organisms often results in the mortality of a large proportion of the population (Cox and Carlson 2012) across all age classes (referred to as an all age epizootic or die-off) and is typically followed by enzootic disease with multiple years of lamb mortality from pneumonia (Brewer et al. 2014). This pattern of pneumonia in wild sheep has been documented in more than 70 peer-reviewed scientific publications. Health assessments of thinhorn sheep have demonstrated far less exposure to various pathogens when compared to bighorn sheep (Jex et al. 2016) |
| Trend (in population, range, area occupied, and/or condition of occurrences) | |
| Short-Term Trend: | G = Relatively Stable (<=10% change) |
| Comments: | Although the population remains relatively stable over the entire range at 10,000-16,000, declines have been noted in some areas of BC, particularly in the Muskwa-Kechika Management Area (M-KMA) where Stone?s sheep (Ovis dalli stonei) population has declined significantly. Possible reasons for the decline include adverse weather conditions, disease, hunting and predation (WLAP 2004, Jex et al. 2016). There also have been significant icing events that reduced neighbouring thinhorn sheep populations in Alaska and Yukon in 2013-16 and potentially in BC (Bill Jex, pers. comm., Troy Hegel, pers. comm.). |
| Long-Term Trend: | EG = Decline of <50% to Relatively Stable |
| Comments: | A range is given as over the long term there have been declines but to what extent is unknown. |
| Other Factors | |
| Intrinsic Vulnerability: | B=Moderately vulnerable |
| Comments: | isolated metapopulations, low fecundity, low dispersal potential, |
| Environmental Specificity: | AB=Very narrow to narrow. |
| Comments: | Habitat models for Stone's sheep in winter and summer seasons identify escape terrain and, secondarily, forage availability as described by ecosystems located within a defined distance to escape terrain (Backmeyer 1995) |
| Other Rank Considerations: | |
| Information Gaps | |
| Research Needs: | Systematic absolute abundance inventories should be completed every 3 - 5 years to obtain a good understanding of Dall Sheep numbers and trends in British Columbia (I. Hatter, pers. comm.; Bill Jex, pers. comm. 2017). |
| Inventory Needs: | Ongoing monitoring of Dall's sheep for indications of disease transmission from domestic sheep and goats. Effective separation of Dall's sheep from domestic sheep and goats. |
| Stewardship | |
| Protection: |
Effective separation is defined as spatial or temporal separation between thinhorn sheep and domestic sheep or goats. Reducing the potential for association between those taxa and the likelihood of transmission of pathogenic organisms or parasites between species is critically important. Maintaining effective separation is presently the only meaningful tool available for minimizing pathogen transfer and the risk of respiratory disease. Habitat management is a concern. Suppression of forest fires may result in a decline of suitable grassland habitat. The number, age, and sex of sheep harvested by First Nations hunters are unknown at present (R. Marshall, pers. comm.; Bill Jex, pers. comm. 2017). Conduct population dynamics studies to investigate current limiting factors on population growth, and impacts of climate related impacts of icing and heavy snowfall related mortality and disease transmission from domestic sheep and goats. |
| Management: | Recent risks associated with potential for disease transmission from domestic sheep and goats and from climate change (icing events and heavy snowfall causing significant population declines in BC and nearby jurisdictions). Extensive management to prevent disease introduction from domestic goats and sheep is needed. |
| Version | |
| Author: | Sean Sharpe, RPBio., M.Sc. |
| Date: | March 13, 2017 |
| References | |
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Western Association of Fish and Wildlife Agencies (WAFWA) Wild Sheep Working Group (WSWG). 2020. Jurisdictional Wild Sheep Population, License, Harvest Demand Estimates, 1990-2019. |
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Bill Jex. 2017. Pers. comm. BC Ministry of Forest Land Natural Resource Operations, Skeena Region, Sheep Biologist.
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Cox, M. and T. Carlson. 2012. Wild Sheep Disease Events & Management Actions among Western States and Provinces. Presentation at the 2012 Western Association of Fish and Wildlife Agencies, Wild Sheep Working Group, Wildlife Professional?s Meeting, Reno, NV.
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Demarchi, R.A., and C.L. Hartwig. 2004. Status of Thinhorn Sheep in British Columbia. B.C. Minist. Water, Land and Air Prot,.Biodiversity Branch, Victoria, BC. Wild. Bull. No. B-119.
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Festa-Bianchet, M. 2020. Ovis dalli. The IUCN Red List of Threatened Species, 2020. Accessed March 2023. https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T39250A22149895.en
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Jex, B. A., J. B. Ayotte, V. C. Bleich, C. E. Brewer, D. L. Bruning, T. M. Hegel, N. C. Larter, R. A. Schwanke, H. M. Schwantje, and M. W. Wagner. 2016. Thinhorn sheep: conservation challenges and management strategies for the 21st Century. Wild Sheep Working Group, Western Association of Fish and Wildlife Agencies, Boise, Idaho, USA.
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Jex, B.A. 2022. Population status and trends -Thinhorn Sheep in British Columbia. Wild Sheep Foundation. Presentation.
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Ministry of Forests. 2022. [DRAFT] Stewardship Framework for Thinhorn Sheep (Ovis dalli) in British Columbia. Thinhorn Sheep Indigenous Perspectives and Thinhorn Sheep Management Teams. Prepared for the Fish and Wildlife Branch, British Columbia Ministry of Forests, Victoria, BC. 69 pp.
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Schwantje, H. 2016. Risk of disease transmission to BC wild sheep herds. Excel spreadsheet presented to Wild Sheep Working Group.
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Sim, Z., C.S. Davis, B. Jex, et al. 2019. Management implications of highly resolved hierarchical population genetic structure in thinhorn sheep. Conserv Genet 20, 185?201.
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Sim, Z., J. C. Hall, B. Jex, T. M. Hegel, and D.W. Coltman. 2016. Genome-wide set of SNPs reveals evidence for two glacial refugia and admixture from postglacial recolonization in an alpine ungulate. Molecular Ecology 2016:1-10 John Wiley & Sons Ltd.
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Wild Sheep Working Group. 2012. Recommendations for Domestic Sheep and Goat Management in Wild Sheep Habitat. Western Association of Fish and Wildlife Agencies. 28 pp.
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Worley, K, C. Strobeck, S. Arthur. 2004. Population genetic structure of North American thinhorn sheep (Ovis dalli). Molecular Ecology, 13:2545?2556.
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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. 2017. Conservation Status Report: Ovis dalli stonei. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Mar 6, 2026).