The geographic range of the species is west of the Great Plains from central British Columbia to central California. There are twelve races, six of them occurring in Washington.
The yellow-pine chipmunk is a small animal, being but little larger than the least chipmunk, and much smaller than townsendii. Externally it may be separated from the Townsend chipmunk by its small size, sleek, appressed pelage and brighter color. Separation from minimus is more difficult but, in the Washington races of minimus, the colored fur of the underside of the tail is pale yellowish while in amoenus it is more ochraceous or buffy. So far as is known, the two species do not occur together in Washington.
The yellow-pine chipmunks live in open woods, brushy areas, clearings, and rocky outcrops. Suitable conditions are abundant in mountainous areas and the distribution of mountain ranges affects the distribution of these chipmunks. Where yellow pine forests descend to relatively low altitudes, the chipmunks enter the lowlands. Such conditions are present in some places along the eastern base of the Cascades, the inter-mountain river valleys of northeastern Washington, and along the central-eastern border of the state.
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.
I have watched these chipmunks eat the berries of the red huckleberry (Vaccinium parvifolium), salmonberry (Rubus spectabilis), thimbleberry (Rubus parviflorus), devil's club (Fatsia horrida), and mountain ash (Sorbus cascadensis and S. occidentalis). Of these, the blue huckleberry (Vaccinum occidentale and V. membranaceum) are probably the most important to the chipmunks. At Sherman Creek Pass, in the Kettle River Mountains, Ferry County, I watched a pika (Ochotona) busily harvesting wild raspberry plants (Rubus leucodermis), and laying them in a pile under a rock. A yellow-pine chipmunk waited under the rock and ate the ripe berries from each branch as it was laid away.
A brood nest of the yellow-pine chipmunk was discovered by [Shaw] (1944: 274) at Hurricane Ridge, Clallam County. The entrance was a hole 1-1/2 inches in diameter constructed among the grass and alpine flowers of a meadow at 6,450 feet elevation. The burrow itself was 2 inches in diameter, and had a turning-around pocket 9 inches from the entrance. The nest was situated just beneath the sod, 4 feet from the entrance. The nest chamber was 7 inches high by 7-1/2 inches in diameter and in the shape of a "round-bottomed flask." It was filled snugly with nest material composed of a grasslike sedge (Carex spectabilis) mixed with feathers of the blue grouse. Earth excavated from the nest cavity had been forced upwards through the sod in the manner of a mole in forming mounds. The single burrow was unbranched. Seven young of about 16 to 18 days of age were found in the nest.
Tamias amoenus caurinus ([Merriam])
Eutamias caurinus [Merriam], Proc. Acad. Nat. Sci. Philadelphia, p. 352, October 4, 1898.