Fig. 57.—Arctic Fox in summer dress.—By permission of the N.Y. Zoölog. Soc.
The American portion of the great Holarctic region is called by Mr. Lydekker, who uses Wallace’s term, the “Canadian subregion,” and by Dr. Merriam the “Boreal region.” Not that there is any difference of principle involved in this varying nomenclature, for Dr. Merriam says: “It so happens that the Boreal element in America resembles that of Eurasia so closely that in the judgment of many eminent authorities the two constitute a single primary region—a view in which I heartily concur.” The Canadian or Boreal subregion of the Holarctic is the great belt of coniferous forest, which extends obliquely across North America from Alaska to New England; its frontier with the Arctic zone is the northern limit of trees and it is divided from the Transition zone approximately by the line of latitude 45° N., though with a sinuous course, and it is carried far to the south by the wooded heights of the Appalachian, Rocky and Sierra Nevada Mountains, and along the Pacific coast, the mixed character of which has already been explained; it extends almost to San Francisco. The subregion is further divisible into northern and southern belts, called the Hudsonian and Canadian faunas, the limit between them approximately following the isothermal line of 57° F. The mammals of this subregion are largely of Old World origin, many of them coming in with the great immigrations of the Pliocene and Pleistocene epochs; but there are also native American elements and even one genus of South American origin, the Short-tailed or Canada Porcupine (Erethizon).
Fig. 58.—Canada Porcupine (Erethizon dorsatus).—By permission of the N.Y. Zoölog. Soc.
Fig. 59.—Woodchuck or Marmot (Marmota monax).—By permission of the N.Y. Zoölog. Soc.
Fig. 60.—Mink (Lutreola vison).—By permission of the N.Y. Zoölog. Soc.
In considering the mammals of this subregion, it should be remembered that they are not uniformly distributed throughout even one subdivision, but in a scattering way and in accordance with their habits and stations, and also in accordance with a gradual change to the south, following the changing temperature. The Muskrat will not be found far from water or the Porcupine from woods. Especially characteristic of the Canadian subregion are the Old World types of deer, none of which range farther south than the Transition zone. The Wapiti, erroneously called the Elk (Cervus canadensis), is very closely allied to the European Stag (C. elaphus) and still more closely to the Stag of the Thian Shan in Central Asia (C. eustephanus). So great is the resemblance, that some naturalists would refer all three forms to a single species. The Moose (Alce americanus), which should be called the Elk, is so near to the Scandinavian Elk (A. machlis) that it is hardly distinguishable as a separate species, and the Woodland Caribou (Rangifer caribou) is the American representative of the Lapland Reindeer (R. tarandus). The so-called Rocky Mountain Goat (Oreamnos montanus), a peculiar and aberrant form of the Chamois subfamily of the Antelopes, is confined to the subregion. The Mountain Sheep (Ovis montana, O. dalli) are represented by three or four species, one of which extends into the Sonoran region, as does also the Bison, wrongly called Buffalo (Bison bison), which is nearly allied to the European B. bonasus. In Cæsar’s time the European Bison (German, Wisent) ranged through Germany and is described in his account of the Hercynian Forest; but the advance of civilization has almost exterminated it, only a few small herds being maintained by the most rigid protection in Russia and in the Carpathian Mountains. Of the Carnivora, the weasels, martens, Fisher, Mink and Ermine are Boreal, as are the Wolverene (Gulo) and the Grey Wolf (Canis), the three last-named extending also into the Arctic zone. Essentially Boreal, though reaching and entering the Sonoran, are the bears (Ursus), the red foxes (Vulpes), the otters (Lutra) and the Old World shrews (Sorex), while the Star-nose Mole (Condylura) and the mole-shrews (Urotrichus) do not extend south of the Transition zone. Probable intruders from the south into the Boreal subregion are the pumas, or “mountain lions,” which just enter the subregion, the Canada Lynx (Lynx rufus) and one species of skunks (Mephitis), the Raccoon (Procyon lotor), Badger (Taxidea americana) and the American deer (Odocoileus). A large number of rodents are characteristically Boreal: marmots, or woodchucks (Marmota), the Sewellel (Aplodontia rufa), lemmings (Myodes), Jumping Mouse (Zapus), the Canada Porcupine (Erethizon dorsatus) and the pikas, “tailless or whistling hares” (Ochotona). Boreal rodents that enter the Sonoran are the chipmunks (Tamias), beavers (Castor), meadow-mice (Microtus), the Muskrat (Fiber zibethicus). The white-footed mice (Sitomys) and the wood-rats (Neotoma) are southern rodents that reach or enter the Boreal.