Geographic Variation in Eutamias quadrivittatus with Comments on the Taxonomy of Other Arizonan Chipmunks

Abstract

Analyses indicate that two subspecies of the chipmunk Eutamias quadrivittatus are recognizable. The widely used name E. q. hopiensis is a syno- nym of E. q. quadrivittatus. A new name is proposed for the other subspecies. The cliff chipmunk in northwestern Arizona is Eutamias dorsalis grinnelli, not E. d. utahensis. The least chipmunk in eastern Arizona is Eutamias minimus operarius, with E. m. arizonensis a synonym of this subspecies. Chipmunks of the species Eutamias quadrivittatus consist of two groups: a large-sized, dark-colored form that usually is found in pine or spruce-fir forests of central and southern Colorado, northern New Mexico, northeastern Arizona, and western Oklahoma; and a small-sized, light-colored form that usually is found in open, juniper- pinyon woodlands among rocks in Utah, north-central Arizona, and western-most Colorado. The differences in size, both externally and cranially, are appreciable and probably are more significant than color, which may be quite variable. The zone of intergradation be- tween these groups is a geographically narrow one in western Colo- rado and northeastern Arizona (see Fig. 1). Analysis of chromosomes of the two groups shows no differences (Sutton and Nadler 1969:528) and according to White (1953b:621-622), the western group has a smaller baculum with a more distinct angle between the tip and shaft. The western group of chipmunks presently is called Eutamias quadrivittatus hopiensis, with the type locality at Keams Canyon, Navajo Co., Arizona. Unfortunately, however, specimens from Keams Canyon do not have the small size characteristic of the western pop- ulations and therefore the name hopiensis cannot be used for the western race. A detailed analysis of specimens from Keams Canyon,