Pacific Water Shrew
Scientific Name: Sorex bendirii
Taxonomy Group: Mammals
COSEWIC Range: British Columbia
COSEWIC Assessment Date and Status Change: April 2016
COSEWIC Status: Endangered
COSEWIC Status Criteria: B2ab(iii,iv)
COSEWIC Reason for Designation: This shrew is restricted to British Columbia’s Lower Mainland and adjacent low valleys. It is rare there, associated with freshwater streams and adjacent wet habitats. Urban development, agriculture, and forestry have reduced the amount and quality of habitat. There is an inferred and projected ongoing decline in habitat and subpopulations in much of its range in Canada.
COSEWIC History of Status Designation: Designated Threatened in April 1994 and in May 2000. Status re-examined and designated Endangered in April 2006. Status re-examined and confirmed in April 2016.
SARA Status: Schedule 1, Endangered
Date of Listing (yyyy-mm-dd): 2003-06-05
Please note that this information is provided for general information purposes only. For the most up to date and accurate list of species listed under the Species at Risk Act, please see the Justice Laws Website.
Image of Pacific Water Shrew
With its small ears, long, pointed snout, and long, slender tail, the Pacific Water Shrew resembles a mouse. It measures 154 mm from the tip of its snout to the end of its tail, and it weighs on average 10.6 g; it is the largest shrew in North America. Its pelage ranges from dark brown to black, with the undersides being slightly lighter. Its long tail is a uniform dark brown. The Pacific Water Shrew has several adaptations for an aquatic lifestyle. For example, its hind feet have a stiff fringe of hairs of up to 1 mm in length that helps it to swim. This species can be confused with the common water shrew, which can be distinguished by its light to black dorsal fur, its silver grey belly, and its two-toned tail, which has a paler underside. (Updated 2017/02/20)
Distribution and Population
The Pacific Water Shrew is found only in western North America, on the Pacific coastal lowlands from northern California through western Oregon and Washington to southwestern British Columbia. In Canada, the species is confined to the lower Fraser River valley region in extreme southwestern British Columbia. It ranges as far east as the Chilliwack River and Harrison Lake. The 142 known occurrence records (sightings and captures) are from about 44 distinct sites. Of the 142 records, 99 are historical museum specimens collected between 1888 and 1957. There are no estimates of Canadian population sizes or long-term trends. The species appears to be rare throughout its range. (Updated 2017/02/20)
The Pacific Water Shrew is generally found in riparian and wetland habitats. This species is associated with skunk cabbage marshes, red alder riparian habitat, and dense, wet forests of western red cedar. Most captures are in riparian habitats in close proximity to water. However, individuals have been captured in forests 25 to 350 m from a stream. Although forested habitats are important, in British Columbia the species has been found in non-forested grassy habitats bordering ditches and sloughs. There are no specific data on habitat trends for this species. However, there has been a loss of wetlands and forests since the early 1900s. (Updated 2017/02/20)
Little information is available on the biology of this species except for its diet. Primarily insectivorous, this mammal feeds mainly on insect larvae, slugs, snails, mayfly nymphs and earthworms. Approximately 25% of its prey is aquatic. This semi-aquatic shrew can swim continuously for up to 3.5 minutes and dive for up to 60 seconds. Air trapped under the fur provides buoyancy and possibly insulation while it is in the water. In Oregon, the breeding period extends from February to August, and females produce two to three litters of five to seven young each. The maximum lifespan is thought to be about 18 months. Owls, domestic cats, fish, and Pacific giant salamanders are thought to be the shrew’s predators. (Updated 2017/02/20)
The main threat to the Pacific Water Shrew is habitat loss and fragmentation. Agriculture and forest harvesting activities have an impact on this species, but development probably poses the greatest threat. In Canada, the Pacific Water Shrew’s distribution coincides with a heavily urbanized area undergoing rapid development and habitat change. In 2004, the combined population of the Greater Vancouver Regional District and the Fraser Valley Regional District was about 2.4 million, an increase of about 11% since 1996. Housing, commercial, industrial and recreational (e.g., golf course) development reduces forested areas and riparian habitats that border streams or wetlands; the habitat is also degraded by run-off and storm water management. The rarity of this species, coupled with its restriction to riparian and wetland habitats, make it susceptible to habitat loss, fragmentation and degradation. Changes in water quality resulting from contaminants could affect the aquatic invertebrates that are eaten by the Pacific Water Shrew. Contaminants such as oil would be expected to reduce the insular efficiency of its pelage. (Updated 2017/02/20)
The Pacific Water Shrew is protected under the federal Species at Risk Act (SARA). More information about SARA, including how it protects individual species, is available in the Species at Risk Act: A Guide.
Provincial and Territorial Protection
Status of Recovery Planning
Recovery Strategies :
Name Recovery Strategy for the Pacific Water Shrew (Sorex bendirii) in Canada
Status Final posting on SAR registry
Pacific Water Shrew Recovery Team
Kym Welstead - Chair/Contact - Government of BC
Phone: 604-582-5279 Fax: 604-930-7119 Send Email
PLEASE NOTE: Not all COSEWIC reports are currently available on the SARA Public Registry. Most of the reports not yet available are status reports for species assessed by COSEWIC prior to May 2002. Other COSEWIC reports not yet available may include those species assessed as Extinct, Data Deficient or Not at Risk. In the meantime, they are available on request from the COSEWIC Secretariat.
18 record(s) found.
- COSEWIC Status Reports (2 record(s) found.)
- Response Statements (2 record(s) found.)
- Recovery Strategies (1 record(s) found.)
- Orders (2 record(s) found.)
- COSEWIC Annual Reports (2 record(s) found.)
- Permits and Related Agreements (5 record(s) found.)
- Consultation Documents (2 record(s) found.)
- Critical Habitat Descriptions in the Canada Gazette (1 record(s) found.)
- Recovery Document Posting Plans (1 record(s) found.)
COSEWIC Status Reports
Response Statement - Pacific Water Shrew (2017-01-11)This shrew is restricted to British Columbia’s Lower Mainland and adjacent low valleys. It is rare there, associated with freshwater streams and adjacent wet habitats. Urban development, agriculture, and forestry have reduced the amount and quality of habitat. There is an inferred and projected ongoing decline in habitat and subpopulations in much of its range in Canada.
Response Statements - Pacific Water Shrew (2006-11-29)The habitat of this rare species, confined to the lower Fraser valley region of British Columbia, continues to decline and fragment as a result of development. There is little chance of rescue. It is extremely rare throughout its range.
COSEWIC Annual Reports
COSEWIC Annual Report - 2006 (2006-08-30)2006 Annual Report to the The Minister of the Environment and the Canadian Endangered Species Conservation Council (CESCC) from the Committee on the Status of Endangered Wildlife in Canada.
COSEWIC Annual Report - 2015-2016 (2016-10-13)Over the past year COSEWIC re-examined the status of 25 wildlife species; of these, the majority (68%) were re-assessed at the same or lower level of risk. Of a total of 45 species assessed, seven were assigned a status of Not at Risk (two re-assessments and five new assessments). To date, and with the submission of this report, COSEWIC’s assessments now include 724 wildlife species in various risk categories, including 320 Endangered, 172 Threatened, 209 Special Concern, and 23 Extirpated (i.e., no longer found in the wild in Canada). In addition, 15 wildlife species have been assessed as Extinct, 54 wildlife species have been designated as Data Deficient, and 177 have been assessed and assigned Not at Risk status.