Variation in the Mountain Goat, Oreamnos americanus (Blainville)

Abstract

The number of mountain goat specimens in major North American collections is still small; 167 skulls were assembled for study. These represent all parts of the geographic range. Absolute cranial dimensions, the coefficients of re- gression of several skull dimensions against basilar length, and the occurrence of epigenetic variations in the skull were recorded. Samples from mountain ranges south of the Peace River-Skeena River trench reveal few or no skull differences between the sexes, but in northern populations there are large differences. Geo- graphic variation is minor. We conclude that there are no valid reasons for recog- nizing subspecies within Oreamnos americanus (Blainville). The mountain goat is now found only in North America. Thus both wide geographic and taxonomic discontinuities exist between the mountain goat and the mountain-antelopes of Eurasia. The present natural distribution of the mountain goat includes most of the mountain ranges on the mainland of western North America from about 44? to 63? latitude. In the northern parts of this range its distribution is irregular. Its northern limits are reached in the Kenai Peninsula and Talkeetna Mountains of Alaska and in the Mackenzie Mountains of the Yukon and Northwest Terri- tories. Southward its range extends through mountainous western Alberta and British Columbia, except for the central plateau. Its souther limits are at the Columbia River in Washington and at the Snake River Plains in Idaho. The coming of European man has not decreased the range of the mountain goat except locally. This may be partly attributed to the mountain habitat of the animal. The only early record north of the present range is that of Schwatka (1885), who reported seeing mountain goats in the mountain ranges along the lower part of the Yukon River in Alaska, but he probably was referring to the white thinhor sheep (Ovis dalli dalli), the distribution of which includes the mountain ranges along the Yukon River. Successful introductions have been accomplished in the Olympic Peninsula, Washington (Washington State Fish and Game Department circular), Sawtooth Mountains, Idaho (Brandborg, 1955), Wasatch Mountains, Utah (personal com- munication), Black Hills of Dakota (Hanson, 1950), Walla Walla Mountains of Oregon, and Baranof, Chichagof, and Kodiak islands in Alaska (Klein, 1965). A liberation on Cowichan Lake, Vancouver Island, did not lead to establishment. The mountain goat, or its immediate progenitor apparently entered North America from eastern Asia in the Pliocene or late Pleistocene via the Bering Land Bridge. It spread along the almost continuous mountain chains, which extend southward in western North America, to reach its southern limits in the sierras of northern Mexico. The successive glacial and interglacial periods of the Pleistocene no doubt resulted in important changes of range and total popu-