BC Conservation Data Centre: Conservation Status Report
Sorex trowbridgii
Trowbridge's Shrew
| Scientific Name: | Sorex trowbridgii |
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| English Name: | Trowbridge's Shrew |
| Provincial Status Summary | |
| Status: | S3 |
| Date Status Assigned: | May 25, 2010 |
| Date Last Reviewed: | March 22, 2024 |
| Reasons: | Although abundant where found, this species is restricted to a declining, fragmented ecosystem in a small area of south western British Columbia. |
| Range | |
| Range Extent: | D = 1,000-5,000 square km |
| Range Extent Estimate (km2): | 4370 |
| Range Extent Comments: | Restricted to the Lower Mainland and Fraser River corridor north to about Boston Bar (Nagorsen 1996; B.C. Conservation Data Centre 1998; Nagorsen and Panter 2024.). Generally rare north of the Fraser River (Zuleta and Galindo-Leal 1994; Nagorsen 1996) with only three confirmed records (Nagorsen and Panter 2024). There are a couple of iNaturalist records (accessed February 2024) in Lynn Canyon and near Sechelt, but these have not been included here as they are non-confirmed. |
| Area of Occupancy (km2): | DE = 6-125 |
| Area of Occupancy Estimate (km2): | 72 |
| Area of Occupancy Comments: | There are 18 2x2 sq km cells occupied. if historical occurrences are not included in AOO calculation. More surveys would undoubtedly discover more locations and thus increase the known Area of Occupancy. |
| Occurrences & Population | |
| Number of Occurrences: | C = 21 - 80 |
| Comments: | There are 18 known extant occurrences; further surveys of regional and provincial parks in the Lower Mainland will likely reveal more. |
| Number of Occurrences with Good Viability / Ecological Integrity: | Rank Factor not assessed |
| Number of Occurrences Appropriately Protected & Managed: | BC = 1 - 12 |
| Comments: | Two of the known occurrences are in protected areas, and it is likely that there are others, as this is where the main suitable habitat is left. |
| Population Size: | E = 2,500 - 10,000 individuals |
| Comments: | The most abundant shrew in the Lower Fraser Valley (Nagorsen 1996). |
| Threats (to population, occurrences, or area affected) | |
| Degree of Threat: | C = Medium |
| Comments: | Urban and agricultural development in the Lower Mainland has caused and continues to cause degradation and fragmentation of suitable habitat (Nagorsen 1996). Habitat fragmentation is also a threat; in a major survey, Trowbridge's Shrews were not found in some small fragments of apparently suitable habitat. Where suburban development borders forests, domestic cats are major predators of shrews (Zuleta and Galindo-Leal 1994). The impact of the recent arrival of large numbers of coyotes in this habitat on small mammals has not been studied (S. Cannings and L. Ramsay, pers. comm. 1998). Logging can also reduce populations (Banfield 1974), though populations can persist in almost any forested habitat within the species' range (Nagorsen 1996). |
| Trend (in population, range, area occupied, and/or condition of occurrences) | |
| Short-Term Trend: | U = Unknown |
| Comments: | No specific trend data are available, but the urbanization of the Lower Mainland has eliminated or degraded much formerly suitable habitat (see Long-term trend and Threats). |
| Long-Term Trend: | EF = Decline of 10-50% |
| Comments: | Much of the forested habitat within the known range of the species has been converted into urban or agricultural land or has been fragmented by these processes. It appears that S. trowbridgii populations can persist in many types and ages of forested habitat, although it was not found in several isolated but seemingly otherwise suitable habitat patches (Zuleta and Galindo-Leal 1994). |
| Other Factors | |
| Intrinsic Vulnerability: | Rank Factor not assessed |
| Environmental Specificity: | CD = Moderate to broad. |
| Comments: | A forest-dwelling species that can apparently persist in many types of forested habitat within its range (Nagorsen 1996). |
| Other Rank Considerations: | |
| Information Gaps | |
| Research Needs: | |
| Inventory Needs: | Surveys should be conducted within the regional and provincial parks of the Lower Mainland to determine the full distribution of this species. Occupied habitat fragmented by development should be monitored to watch for local declines or extirpations. |
| Stewardship | |
| Protection: | |
| Management: | Establish protected areas south of the Fraser River in any areas left with forest, particularly mature growth. Ensure that protected areas where Trowbridge's Shrew does occur are left in a natural state. |
| Version | |
| Author: | Ramsay, L. (2024), Teucher, A.(2009) |
| Date: | January 09, 2024 |
| References | |
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Banfield, A. W. F. 1974. The mammals of Canada. University of Toronto Press, Toronto, Canada. 438 pp.
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British Columbia Conservation Data Centre. 1998. Unpubl. files. B.C. Minist. Environ., Lands and Parks, Resour. Inventory Branch, Victoria, BC.
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Nagorsen, D. 1990. The mammals of British Columbia: a taxonomic catalogue. Mem. No. 4. Royal B.C. Mus., Victoria. 140pp.
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Nagorsen, D. and N. Panter. 2024. Shrews and Moles of British Columbia. Second Edition. Royal BC Museum Handbook. 239 pp.
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Nagorsen, D.W. 1996. Opossums, Shrews and Moles of British Columbia. Royal B.C. Mus. Victoria, BC. 169pp.
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Zuleta, G.A., and C. Galindo-Leal. 1993. Distribution and abundance of small mammals at risk in a fragmented landscape. Unpubl. rep. for B.C. Minist. Environ., Lands and Parks, Wildl. Branch, Victoria. 34pp.
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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. 2024. Conservation Status Report: Sorex trowbridgii. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Oct 3, 2026).