| Colorado chipmunks are solitary and territorial, and adults avoid each other except during the breeding season. Males emerge from their burrows in the spring ready to mate. Females emerge a week or two later, and are receptive for only a few days. Gestation lasts about a month, and the young first appear aboveground when they are about 25 days old and three-fourths adult size. Sometimes Colorado chipmunks breed again in the summer and have a second litter. They are a great deal like least chipmunks in their activity cycles, reproduction, foraging behavior, and vocalizations, but curiously enough, when a Colorado chipmunk vocalizes it sways its tail from side to side, and when a least chipmunk vocalizes it flicks its tail up and down.
Females are slightly larger than males.
Say, T., 1823. in Account of an expedition from Pittsburgh to the Rocky Mountains : performed in the years 1819 and ’20, by order of the Hon. J.C. Calhoun, sec’y of war, under the command of Major Stephen H. Long : from the notes of Major Long, Mr. T. Say, and other gentlemen of the exploring party compiled by Edwin James, botanist and geologist for the expedition; in two vols., H.C. Carey and I. Lea, Philadelphia,1822-23. Vol 2, p 45-47.
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Mammal Species of the World
Mammalian Species, American Society of Mammalogists' species account
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