Postglacial Distribution Patterns of Mammals in the Southern Coastal Regions of Alaska

D URING the Wisconsin glaciation the present land areas of the coastal regions of Alaska bordering the Gulf of Alaska were virtually completely overridden by ice. The now existing flora and fauna of the region have presumably become established in the 10,000 years since the recession of the ice. Swarth discussed the origins of the fauna of the “Sitkan District’’ in 1936, and since then additional knowledge of the glacial history of the southern coastal regions of Alaska has become available, permitting a new interpretation of the distribution patterns of mammals (Heusser 1960, Miller 1958, Flint 1957, and Karlstrom 1964). The present distribution of mammals in this region, although complicated by the phenomenon of insularity, reflects the sequence of their arrival and their relationship to specific refugia. A brief review of the late-Wisconsin geology and postglacial vegetation of the southern coastal areas of Alaska will serve as a useful base for understanding the mammalian distribution patterns of the region. Heusser (1960) has shown that the ice, covering virtually all this region, receded about 10,000 years ago. The islands of the Alexander Archipelago were apparently free of ice at least a few hundred years before the adjacent mainland whereas in Prince William Sound, on the Kenai Peninsula, and on Kodiak Island glacial recession took place approximately 1,000-2,000 years later than in the Alexander Archipelago. In the intervening region of the mainland, from Mt. Fairweather to Cape Suckling, late-Wisconsin ice apparently did not cover much more land than is now occupied by glaciers although major postglacial tectonism has been a complicating factor in this area (Miller 1958). As the ice melted, associated changes in sea-level took place. In the Alexander Archipelago it is probable that during the Wisconsin glacial maximum, sea-level was lower than at present, exposing greater expanses