ABSTRACT
Quite a high number of northern pikas was observed in September 1956 in the middle fork of the Ortoku-Ukhta River (northwest of the Verkhoyansk Range), where about 30 individuals/ha (Kapitonov, 1961) lived. A similar number of northern pikas was found in some areas in the basin of the Olekma and on the western edge of the Yukagirsk Plateau (Krivosheev, 1971). In southern Yakutia, on the Olekma-Charsk upland (near the mouth of the Charoda River) in old burned-out forests with rock slides and stony mounds in April-May 1963, the number of northern pikas was very high50-75 individuals/ha. A still higher number of northern pikas was recorded at the end of July 1964 on rock dumps and on slopes of supraflood plain terraces in the mouth of the Sykra River-about 100 individuals/ ha. In places with weakly dissected relief or on edges of stony mounds in the basin of the Tokko River, in the middle of June 1961, the number of northern pikas was low-10 individuals/ha (Revin, 1968). On the whole, for Yakutia an insignificant fluctuation of numbers from year to year is characteristic for northern pikas (Krivosheev, 1971).
