Western harvest mouse (Reithrodontomys megalotis) COSEWIC assessment and update report: chapter 1

Assessment Summary

Assessment Summary – April 2007

Common name : Western harvest mouse megalotis subspecies

Scientific name : Reithrodontomys megalotis megalotis

Status : Special Concern

Reason for designation : This subspecies has a limited range, and a small extent of occurrence and area of occupancy. However, the extent of occurrence and area of occupancy appear to be constant. Its principal native habitat in the Okanagan as well as old fields is declining. Furthermore, old apple orchards where the mouse has been caught are being converted to vineyards. Dispersal distance is limited and the likelihood of rescue effect is small. Extensive sampling has revealed the occurrence of the mouse at more localities. 61,000 hectares of suitable habitat is protected.

Occurrence : British Columbia

Status history : Designated Special Concern in April 1994 and in April 2007. Last assessment based on an update status report.

 

Assessment Summary – April 2007

Common name : Western harvest mouse dychei subspecies

Scientific name : Reithrodontomys megalotis dychei

Status : Endangered

Reason for designation : This subspecies has a limited range and has been found at only one location in the past 40 years; this location is isolated from others. Dispersal distance is limited and the population flutuates. This species is commonly found in owl pellets in the USA, but none have been reported in owl pellets (including burrowing owls) in Suffield or other areas in southeast Alberta, despite substantial sampling. Owl pellet analysis is an excellent means of sampling for these mice.

Occurrence : Alberta

Status history : Species considered in April 1994 and placed in the Data Deficient category. Re-examined in April 2007 and designated Endangered. Last assessment based on an update status report.

 

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