Yellow-pine chipmunks are sprightly and active. They seem always to be moving restlessly about, running, investigating for food, and watching for enemies. They are far tamer than the least chipmunks, usually allowing the observer to approach within twenty feet or closer. Some, after coaxing, will take food from a person's hand. Near Stevens Pass, King County, numbers of _Tamias townsendii cooperi_ and _Tamias amoenus ludibundus_, apparently on good terms, were feeding together on blue huckleberries which grew in abundance on an extensive snowslide area. The yellow-pine chipmunks had been drawn from surrounding open areas by the berries, while the Townsend chipmunks had been attracted from the forest by the same food. The nervous movements of _amoenus_ contrasted strongly with the more sedate behavior of _townsendii_. At the observer's close approach the yellow-pine chipmunks went scampering off through the brush and tangles of logs and branches, to emerge again and watch from a hundred feet away. The same individuals, when repeatedly followed, always remained in sight. Most of the Townsend chipmunks, when frightened, ran into the nearest dense cover and vanished, not to appear again. A goodly number, perhaps ten per cent, climbed high up in fir trees. None of the yellow-pine chipmunks took refuge in trees. The yellow-pine chipmunk is usually found at considerable altitude and consequently there is deep snow and bitter cold in winter where it lives. Hibernation is probably complete. Seemingly these chipmunks depend on stored food rather than on accumulated fat to tide them over the winter, for animals collected in autumn are no fatter than those taken in the spring. Svihla (1936B: 290) found that _Tamias a. canicaudus_, hibernating in captivity at Pullman, Whitman County, awoke at intervals to eat stored food. The time of retirement of yellow-pine chipmunks for the winter seems to coincide with the coming of winter weather. In mid-November of one year, when no snow had yet fallen in the Cascades, yellow-pine chipmunks were common near Stevens Pass, although their actions were noticeably slow. In another autumn, when the winter snows came early, I looked in vain for chipmunks in October where they had been common earlier. George C. Cantwell noted a yellow-pine chipmunk at Republic, Ferry County, on November 9, 1903, after the ground was "well frozen," but apparently free of snow (Howell, 1929: 7). Like other species that hibernate, they, at times, seem to become active in winter; J. B. Flett reported seeing a yellow-pine chipmunk at Longmire, Mt. Rainier, on February 14, 1920, and again on March 31 (Howell, _loc. cit._, p. 7). At Deer Park, Clallam County, at timber-line, several _Tamias townsendii cooperi_ were active in early April, 1938, but only one _Tamias amoenus_ was seen. In the previous June they were abundant there and _townsendii_ was scarce.