Tamias sp.—Chipmunks // Tamias canipes/quadrivittatus—Gray-footed or Colorado Chipmunk // Tamias canipes—Gray-footed Chipmunk // Tamias minimus—Least Chipmunk
Synonyms. Eutamias, Neotamias. Western chipmunks have widely been placed in the genus Eutamias, and the genus Neotamias also has been used. To quote Thorington and Hoffmann (2005:813), "Thus, a single genus, Tamias, may be employed for all chipmunks (Levenson et al., 1985), but two genera (Tamias and Neotamias) could be recognized, or all three could be recognized as genera." We follow Thorington and Hoffmann here in considering all of our chipmunks to belong to the genus Tamias.
Chipmunks are small squirrels limited, in our region, to montane situations. In the Trans-Pecos, they are limited to the higher portions of the Guadalupe Mountains and the Sierra Diablos (Schmidly 2004). In New Mexico and Arizona, chipmunks are expected in ranges that support woodland or higher-elevation vegetation. Where more than one species occurs, there generally is an elevational division of habitat; where only a single species occurs, it generally encompasses an elevational range greater than when another species is present.
Chipmunks can be confused with other small sciurids. but dental characters and the nature of the infraorbital foramen (Figs. 1 and 2) will separate them (see figure 2 in the Sciuridae account for lower dentition differences). Within the genus, however, identification to species is difficult. Fling (1997) attempted to discriminate among the regional taxa through tooth measurements. Tamias minimus, a notably small-sized species, was the only taxon reliably separated from the others. Qualitative differences in teeth among the species are unknown. In light of this, identifications of species other than T. minimus must be considered highly speculative and, in practice, based on geographic considerations.
A chipmunk from U-Bar Cave (Fig. 1) is larger than any measured by Fling (1997). His largest measurement of the upper toothrow is 6.2 mm for T. cinereicollis. The specimen figured has an estimated minimum toothrow length of 7.2 mm.
Fig. 1. This Wisconsin-age Tamias shows two characters typical of chipmunk maxillae and upper dentition. The infraorbital opening can be seen as a simple hole through the zygomatic plate (just above the masseteric tubercle in the figure), and the divergence of the lophs of M1 and M2 is clearly visible. Scale in mm.
The absence of Tamias from the extensive late Wisconsin faunas from Dry Cave is puzzling. The hypothesized vegetation (Harris 1989) should have supported them. Tamias minimus, for example, inhabits similar habitat in modern areas most similar to those thought to have been present at Dry Cave. Chipmunks were present at contemporaneous faunas in the southern Guadalupes and also at Dry Cave during the interstadial earlier faunas.
1997; Harris 1989;
Schmidly 2004; Thorington and Hoffmann
Chipmunks identified to genus-only recognizes the difficulty in identifying these rodents to the species level. Two records (Baldy Peak Cave and Mid Wisconsin U-Bar Cave) were originally reported as T. ? cinereicollis and T. ? dorsalis respectively. They currently are considered to be unidentifiable to species.
The record of Tamias at Conkling Cavern appears to not be documented with specimens and is withdrawn pending further investigation.
Rancholabrean: Anthony Gap Cave (UTEP); Papago Springs Cave (Skinner 1942).
Early/Early-Mid Wisconsin: Lost Valley (Harris 1993c).
Mid Wisconsin: Papago Springs Cave (Czaplewski and Mead et al. 1999); U-Bar Cave (Harris 1987).
Mid/Late Wisconsin: Rampart Cave (Lindsay and Tessman 1974).
Mid Wisconsin-Holocene: Shelter Cave (UTEP)
Late Wisconsin: Big Manhole Cave (Harris 1993c); Lower Sloth Cave (Logan 1983); Muskox Cave (Logan 1981); Nankoweap Canyon (Cole and Mead 1981); Tucson Mountains (Mead et al. 2005); U-Bar Cave 14-15 ka (Harris 1989); U-Bar Cave 15-18 ka (Harris 1989); U-Bar Cave 18-20 ka (Harris 1989).
Late Wisconsin/Holocene: Baldy Peak Cave (Harris 1993c); Conkling Cavern (Harris 1993c; Rejected).
Literature. Cole and Mead 1981; Czaplewski and Mead et al. 1999; Harris 1987, 1989, 1993c, 2003; Lindsay and Tessman 1974; Logan 1981, 1983; Mead et al. 2005; Skinner 1942.
Identification to species is based on geographic grounds. Currently, T. canipes is found in the southern mountains east of the Rio Grande Valley. The Colorado Chipmunk is primarily northern, but evidence of occurrence far to the south is seen in its presence as a relictual population in the Organ Mountains (Findley 1987). Thus, either of these two species are potentially possible.
Fig. 1. Colorado Chipmunk. National Park Service photograph by Sally King.
Sites. Mid Wisconsin: Pendejo Cave (Harris 2003).
Late Wisconsin:Dust Cave (Harris and Hearst 2012).
Literature. Findley 1987; Harris 2003; Harris and Hearst 2012.
Synonyms. Tamias cinereicollis. In 1960, Fleharty split T. cinereicollis into the western populations that kept the name T. cinereicollis and resurrected the name T. canipes for populations in the southern mountains east of the Rio Grande. Dalquest and Stangl (1984b) for whatever reason used the earlier name, but made it clear that they meant the taxon that currently inhabits the Guadalupe Mountains. The assignment to species was only tentative. Likewise, the Sierra Diablo specimen is assigned to this species on the basis of distribution and that it is not T. minimus.
Tamias canipes is limited today to the mountains from the Gallinas south to the Guadalupes (Findley 1987), and Schmidly (2004) notes that they also are recorded from the Sierra Diablo of Trans-Pecos Texas.
Mid/Late Wisconsin/Holocene: Sierra Diablo Cave (UTEP).
Late Wisconsin/Holocene: Fowlkes Cave (Dalquest and Stangl 1984b).
Literature. Dalquest and Stangl 1984b; Findley 1987; Fleharty 1960; Schmidly 2004.
The Least Chipmunk has relictual distributions in the southeastern New Mexico mountains, but is common in the northern mountains. There also is a relictual population in the White Mountains of eastern Arizona.
Fig. 1. Least Chipmunk. National Park Service photograph by Sally King.
Tamias minimus is enough smaller than other regional species of Tamias to allow reasonably secure species identification. The Bat Cave is of special interest because it lies about halfway between western (White Mountains of Arizona) and eastern (Sierra Blanca/Sacramento Mountains of New Mexico), demonstrating rather nicely continuous distribution between present-day highlands.
Mid Wisconsin: Pendejo Cave (Harris 2003).
Late Wisconsin: Dust Cave (Harris and Hearst 2012); Sheep Camp Shelter (Gillespie 1985: cf.).
Late Wisconsin/Holocene: Bat Cave (Scarbrough 1986); SAM Cave (Rogers et al. 2000).
Literature. Gillespie 1985; Harris 1993c, 2003; Harris and Hearst 2012; Scarbrough 1986; Rogers et al. 2000.
Last Update: 25 Sep 2013