Fringed bat COSEWIC assessment and status report: chapter 4

Distribution

Global range

The Fringed Bat ranges throughout western North America from Chiapas and Veracruz, Mexico, across much of the western United States to southern British Columbia (Figure 2). A disjunct population inhabits the Black Hills of South Dakota and Wyoming (O’Farrell and Studier 1980). The limits of its distribution in the coastal Northwest are not clear. Most distribution maps (e.g., O’Farrell and Studier 1980) show a coastal population in California and Oregon that reaches its northern limits at the Columbia River. Although Barbour and Davis (1969) and Manning (1993) noted the occurrence of this species in coastal Washington, the Washington records summarized by Johnson and Cassidy (1997) show no coastal occurrences. A specimen from Olympic National Park on the Olympic Peninsula identified as the Fringed Bat by Scheffer (1995) (see Appendix 1) suggests that the coastal range may extend north of the Columbia River.

Figure 2. Global range of the Fringed Bat (Myotis thysanodes).

Global range of the Fringed Bat (Myotis thysanodes)

Canadian range

In Canada (Figure 3), this bat is restricted to southern British Columbia where it is generally found below 800 m in valleys of the dry interior grasslands (Nagorsen and Brigham 1993). This species was first discovered in Canada in 1937 when Maslin (1938) found a nursery colony in a house at Vernon. Subsequent surveys (Fenton et al. 1980; Collard et al. 1990; Roberts and Roberts 1992, 1993; Firman et al. 1994; Holroyd et al. 1994; Sarell and Haney 2000) demonstrated that the Fringed Bat inhabits the Okanagan, Similkameen, north and south Thompson, Fraser and Chilcotin River valleys (Fig. 3). Northernmost occurrences are Grinder Creek near Williams Lake in the Fraser River and the Farwell Canyon in the Chilcotin River. The occurrence of this species in coastal Washington (see Scheffer 1995; Appendix 1) raises the possibility of the Fringed Bat inhabiting coastal areas in south-western British Columbia.

The 33 distributional records in Canada represent about 18 element occurrencesFootnote1. The distributional records in the Cariboo and Fraser river valleys appear to be isolated from those in the Thompson, and southern Okanagan-Similkameen valleys suggesting the existence of two subpopulations. Nevertheless, this disjunct pattern may be largely an artifact of sampling. Little bat inventory has been done the Thompson River valley or the Fraser River valley between Lillooet and Churn Creek.

Figure 3. Canadian range of the Fringed Bat (Myotis thysanodes).

 Canadian range of the Fringed Bat (Myotis thysanodes)

Historical distributional changes can not be assessed because the Canadian range has only been delimited over the past few decades. The area of occupancy is unknown; the extent of occurrence in Canada is about 8,650 km². This represents less than 5% of the species' global range.

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