Pacific water shrew (Sorex bendirii) COSEWIC assessment and status report: chapter 11

Sorex bendirii

Pacific water shrew – musaraigne de Bendire

Range of Occurrence in Canada:

British Columbia

Extent and Area Information

Extent of occurrence (EO) (km²)

3,350 km² (see Map (Figure 3) of historical and recent occurrences)

Specify trend in EO

Unknown

Are there extreme fluctuations in EO?

No

Area of occupancy (AO) (km²)     -

Unknown

Specify trend in AO     -

Are there extreme fluctuations in AO?

-

Number of known or inferred current locations

44

Specify trend in #

Unknown

Are there extreme fluctuations in number of locations?

No

Specify trend in area, extent or quality of habitat

Habitat declining

Population Information

Generation time (average age of parents in the population)

1 year

Number of mature individuals

Unknown

Total population trend:

Unknown

% decline over the last/next 10 years or 3 generations.

Are there extreme fluctuations in number of mature individuals?

No

Is the total population severely fragmented?

Yes

Specify trend in number of populations

-

Are there extreme fluctuations in number of populations?

-

List populations with number of mature individuals in each:

Threats (actual or imminent threats to populations or habitats)

  • Habits loss and habitat fragmentation from urban development (roads, housing, commercial, industrial)
  • Habitat loss from forest harvesting
  • Water quality degradation from development

Rescue Effect (immigration from an outside source)

Status of outside population(s)?

USA: Washington S4, status in county bordering Canada unknown

Is immigration known or possible?

Yes

Would immigrants be adapted to survive in Canada?

Yes

Is there sufficient habitat for immigrants in Canada?

No?

Is rescue from outside populations likely?

No?

Quantitative Analysis

Current Status

COSEWIC: Threatened in April 1994 and May 2000; Endangered in April 2006

Status and Reasons for Designation

Status:  Endangered

Alpha-numeric code: B1ab(i,iii)

Reasons for Designation: 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.

Applicability of Criteria

Criterion A: While there is no direct evidence of a declining population trend, the available habitat is rapidly declining. However, there are no data on population size. It appears to be rare throughout its range.
Criterion B: EO less than 5,000 km²; AO is unknown; Continued decline in suitable habitat and remaining habitat patches are highly fragmented.
Criterion C: Total population size is unknown but likely in the thousands.  No direct evidence for decline, but suitable habitat has declined dramatically.
Criterion D: Total population size is unknown but likely in the thousands.
Criterion E: Not available.

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