SHREWS

Common (Masked or Cinereus) Shrew Dlodettha Sorex cinereus

The common shrew occurs throughout the Yukon to the north coast and is likely the most common and widely distributed of the shrews of the Old Crow Basin. Northern Yukon specimens in museums are from Old Crow, 95 km northeast of Old Crow, Driftwood River, and Rampart House (Youngman 1975). In the Yukon, common shrews have been collected in almost every habitat from stabilized talus slopes to wet, mossy areas and at elevations between 24 and 1300 m (Youngman 1975). Humidity seems to be an important factor in habitat selection and common shrews use runways on the moist forest floor (Banfield 1974) and trails near water (Youngman 1975). Averaging 100 mm in length, this shrew feeds mostly on insects, but also eats small vertebrates and other inverebrates.

Tundra Shrew Sorex tundrensis

The present North American distribution of the tundra shrew is completely within Beringia, the unglaciated areas of Alaska, Yukon and the District of Mackenzie in the NWT (Youngman 1975). Banfield (1974) considered this shrew a subspecies of the arctic shrew (Sorex arcticus), but stated that it "may consitute a distinct species." The range of this species extends across the eastern half of Russia. Specimens noted by Youngman (1975) are from Old Crow and the Firth River south of Joe Creek. Its habitat is drier than that of other shrews and it may be found in plant communities with no overhead vegetation. The winter fur is long and silky, with brown on the back, sides and belly greyish. In summer the sides are pale brownish-grey (van Zyll de Jong 1984). Size (115 mm in length), robust build, and a relatively short tail helps to identify this species (Banfield 1974).

Barrenground Shrew Sorex ugyunak

Formerly grouped with the common shrew, the barrenground shrew occurs in North America along the arctic coast from Alaska to Hudson Bay and inland almost to Great Slave Lake (van Zyll de Jong 1984). One specimen is known from the Driftwood River, 96.5 km northeast of Old Crow. This small (82 mm), short-tailed shrew is distinctively coloured with the light grey-brown colour of the undersides extending far up the sides. The brown back features a dorsal stripe. Inhabiting the arctic tundra north of the tree line, it appears to select low, wet, sedge-grass meadows and thickets of dwarf willow and birch. It has been found in old Inuit winter houses and has been observed to enter and feed on winter food caches (van Zyll de Jong 1984).

Dusky Shrew Sorex monticolus

The dusky shrew lives in western North America and probably occurs throughout the Yukon. The northernmost specimen from the Yukon recorded by Youngman (1975) is from Old Crow, though a specimen from Tuktoyaktuk, NWT, suggests it probably reaches the northern Yukon coast. This shrew has been trapped in moist habitat in grass, deep moss, and dwarf alder between sea level and 2000 m elevation. The habitat of the dusky shrew is near streams and springs where shrub vegetation provides overhead protection and ground cover is relatively sparse. With an average length of 118 mm and similar in colour to the masked and tundra shrews, the teeth of the upper jaw are the best way of distinguishing this shrew. The third upper unicuspid (one cusp or point) tooth is smaller than the fourth (Banfield 1974).

Pigmy Shrew Sorex hoyi

Although this shrew is only known from the southern half of the Yukon (Dawson), Youngman's range map suggests that the species may occur in the Old Crow area (Youngman 1975). With an average length of 85 mm, the pigmy shrew is one of the smallest mammals in the world, and one of the rarer of the American small mammals (Banfield 1974). Smaller, slimmer, and greyer than the masked shrew, and with a decidedly shorter tail, certain identification of a pigmy shrew depends on the presence of two tiny and three large unicuspid teeth in the upper jaw. All other long-tailed shrews have five large unicuspid teeth. An inhabitant of the boreal forest zone, the pigmy shrew occupies grassy glades within the forest, sphagnum bogs, and shrubby borders of bogs and wet meadows. Insects are thought to be the major food source, though this shrew, like others, also eats other small mammals when available (Banfield 1974).

Several of the shrews that are known or might be expected from Vuntut National Park are illustrated in Figure 12.1a.