. The Canadian field-naturalist. 592 The Canadian Field-Naturalist Vol. 110. Figure 5. Approximate extent of glaciers during the Late-Wisconsin (Fraser) about 18 000 yr B. P. Arrows indicate possi- ble ice free refugia found along the North Gulf Coast during this period (Heusser 1960; Hopkins 1967; Heusser 1989; and references therein). arctos in Southeast Alaska are consistent with this hypothesis (Talbot and Shields 1996). The discovery of pre-Fraser marmot teeth found on Prince of Wales Island is of particular interest (Heaton 1995). Today, Marmota caligata occurs only on the mainland, and
. The Canadian field-naturalist. 592 The Canadian Field-Naturalist Vol. 110. Figure 5. Approximate extent of glaciers during the Late-Wisconsin (Fraser) about 18 000 yr B. P. Arrows indicate possi- ble ice free refugia found along the North Gulf Coast during this period (Heusser 1960; Hopkins 1967; Heusser 1989; and references therein). arctos in Southeast Alaska are consistent with this hypothesis (Talbot and Shields 1996). The discovery of pre-Fraser marmot teeth found on Prince of Wales Island is of particular interest (Heaton 1995). Today, Marmota caligata occurs only on the mainland, and is thought to be of south- em origin (Youngman 1975). Heaton (1995) noted that the marmot molar found on Prince of Wales Island was smaller than Marmota caligata, and sim- ilar in size to Marmota flaviventris, found farther south and east. Alternatively, this marmot may be more closely related to M. broweri or M. camtschat- ica, small-bodied species of marmots now occurring on the west and east sides, respectively, of what was once Beringia (see Hoffmann et al. 1979). Or, it may be related to other smaller-bodied forms of marmots including M. c. vigilis, an endemic sub- species from Glacier Bay; or M. c. sheldoni, another smaller-sized endemic, last seen in 1908 on Montague Island, Prince William Sound (Howell 1915; Hoffmann et al. 1979). A northern origin for the Prince of Wales Island marmot, rather than southern as mentioned by Heaton (1995), is consis- tent with the affinities of most of the fossil mam- mals found recently. Since most of these fossils are of Holarctic, tundra-adapted species, we propose that, similar to hypotheses advanced for human migration into the New World (Fladmark 1979), a corridor existed along the coast from southern Beringia to the southern end of Cordilleran ice sheet (Figure 4) from the last interstadial to the early Holocene. Such a corridor implies a connection along the continental shelf which was exposed by a lowered sea level (Figure 4) and
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