Keen's long-eared bat (Myotis keenii) COSEWIC assessment and status report: chapter 4

Distribution

Because of identification problems in areas where M. keenii is sympatric with M. evotis, occurrence records from areas other than Haida Gwaii (where M. keeniiis the only long-eared Myotis species) are restricted to museum voucher specimens identified from morphometric traits described by van Zyll de Jong and Nagorsen (1994), or voucher specimens or captured animals released alive that were identified from mtDNAanalysis of tissue samples (Dewey, unpublished data).

Global range

M. keenii is restricted to western Washington State, western British Columbia, and southeastern Alaska (Figure 3). In Washington, this species inhabits the Olympic Peninsula and the Puget Sound area including Whidbey and San Juan Islands. Southern limits of its range appear to be delimited by the Columbia River. In Alaska, M. keenii is known from four islands (Chichagof, Prince of Wales, Revillagigedo, and Wrangell) in the Alexander Archipelago. Although there are no records, this bat probably also inhabits the adjacent coastal mainland of the Alaska panhandle.

Canadian range

In Canada, M. keenii is restricted to British Columbia (Figure 3) where it occurs on the coastal mainland as far north as Telegraph Creek in the Stikine River valley, four islands in Haida Gwaii (Kunghit, Gandl K'in Gwaayaay = Hotspring IslandFootnote2 , Graham, Moresby), and Vancouver Island and associated islands (Denman Island). While its main BCrange is on coastal islands and the mainland coast and coastal mountains, recent captures at Nine Mile Creek in the Skeena Mountains demonstrate that M. keenii ranges east of the Coast Mountains into the British Columbia interior. A survey by Firman et al. (1993) using mist nets and bat traps is the only coastal bat survey with data on species captured at each survey site. They captured long-eared Myotis at only 5 of 51 sites, but since they took few vouchers and no tissue samples, most of their long-eared Myotis captures can only be identified as M. keenii/M. evotis. In a similar survey of the Skeena Management District by Mackay et al.(2000), long-eared Myotis were captured or detected at 13 of 46 sites, but M. keenii and M. evotis were only confirmed (by voucher specimens) at 1 site. Locations sampled by both surveys are shown in Figure 4. The data from these two surveys suggest a spotty distribution, although the results may be biased because each site was only sampled on 1 or 2 nights.

Figure 3. Distribution of Keen’s long-eared bat (Myotis keenii) in North America. Location records are based on historical museum specimens identified from morphometric traits or recent voucher specimens or captured animals identified from mtDNA analysis of tissue samples. Magnetic north is indicated.

Figure 3. Distribution of Keen’s long-eared bat (Myotis keenii) in North America.  Location records are based on historical museum specimens identified from morphometric traits or recent voucher specimens or captured animals identified from mtDNA analysis of tissue samples. Magnetic north is indicated.

Because of inadequate and unsystematic inventory efforts, the distributional limits ofM. keenii, particularly on the coastal mainland of British Columbia, are not well defined. No data exist to assess historical range changes. Some records of occurrence are historical museum specimens that were collected 50 to 120 years ago. No modern surveys have been done to verify that populations still exist at these locations. To what extent the Canadian range is fragmented is unknown. The few scattered mainland records largely reflect sampling bias and this bat may be continuously distributed throughout most of the coastal mainland. The degree of isolation among the island populations has not been studied. The most isolated island population is associated with Haida Gwaii, an archipelago that lies about 68 km from the adjacent mainland separated by the open waters of Hecate Strait. The extent to which M. keenii move between the Haida Gwaii and the mainland is unknown, but the M. keenii associated with this archipelago should probably be treated as a distinct subpopulation.

Figure 4. Fifty-three locations sampled by Firman et al. (1993) during a coast-wide survey for Keen’s long-eared bat (Myotis keenii), and 46 sites sampled by MacKay et al. (2000) during a survey of the Skeena Management District. Squares= sites where either the western long-eared bat (M. evotis) or M. keeniiwere captured; circles= sites where no long-eared Myotisspecies were captured.

Figure 4. Fifty-three locations sampled by Firman <em>et al.</em> (1993) during a coast-wide survey for Keen’s long-eared bat (Myotis keenii), and 46 sites sampled by MacKay <em>et al.</em> (2000) during a survey of the Skeena Management District. Squares= sites where either the western long-eared bat (M. evotis) or M. keenii were captured; circles= sites where no long-eared Myotis species were captured.

Because the distribution of actual populations is unknown, the area of occupancy for M. keenii cannot be determined. Its extent of occurrence in Canada is about 268,830 km² (mainland= 226,500 km², Haida Gwaii= 9,130 km², Vancouver Island=33,200 km²). This represents about 80% of their global geographic range.

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