Tamias minimus 327Oregon, and southwestern Idaho, south to the eastern
side of the Sierra Nevada in California, and west into Ne-
vada (USA). This form is smaller, with cinnamon sides.
This form is similar to T. m. consobrinus, but T. m. scruta-
tor is lighter colored and less rufescent. In comparison
with T. m. pictus, T. m. scrutator has a shorter tail, and the
top of the head is darker.
T. m. selkirki—known only from the type locality at Paradise
Mine, near Toby Creek, 19 miles west of Invermere, Brit-
ish Columbia (Canada). The outer dark stripes are brown,
and the inner dark stripes get blacker. The inner light
stripes are heavily colored with gray and brown. The
postauricular patch is grayish white. The sides are cin-
namon buff. The undersurface of the tail is between
pinkish cinnamon and cinnamon buff.
T. m. silvaticus—region around the boundary between Wyo-
ming and South Dakota (USA). This form is large, and the
general color is drab. The sides are ochraceous buff. The
ventral surface of the tail is ochraceous orange fringed
with black. In comparison with T. m. pallidus, T. m. silvati-
cus has darker and redder upperparts. The dorsal stripes
and the top of head are darker.
conservation: IUCN status—least concern. Population
trend—stable. T. m. atristriatus is critically endangered, and
T. m. selkirki is vulnerable.
habitat: T. minimus lives in open areas relatively free of
downed woody debris, and in a riparian system along the
Green River (upland riparian habitat in Utah, Wyoming, and
Colorado [USA]). Microhabitat use by the least chipmunk is
often determined by the presence of conspecifi cs. For ex-
ample, in western Colorado in the pinyon-juniper-sagebrush
community (Pinus edulis, Juniperus scopulorum, Artemisia), T.
minimus occurs close to trees, except when T. rufus is abun-
dant; T. minimus then shifts to the surrounding sagebrush
habitat.
natural history: This species is largely granivorous, but
its diet depends on the seasonal availability of other foods
and frequently includes fruits and fl owers, arthropods (pri-
marily insects), and leaves. The least chipmunk is reported
to construct leaf nests or occupy tree cavities, although it
most commonly relies on underground burrows for hiber-
nation and nesting. Such burrows are relatively shallow
(0.5–1 m deep), short (0.4–3.5 m long), and usually have one
to three entrances and one or two chambers. Extensive lar-
der-hoards of food are not reported from the nests of T. mini-
mus. Females enter estrus within seven days of emergence.
Gestation is 28–30 days. Average litter sizes across this spe-
cies’ range, estimated from embryo counts and placental
scars, average 4.0–6.4 and 4.0–5.5, respectively. This species
typically produces only one litter per year. Lactating fe-
males are reported as early as May and as late as August,
depending on the location. Home range in one study in Al-
berta (Canada) averaged 1.22 ha and 0.66 ha for males and
females, respectively. Most other estimates are based on
trapping data, and they are substantially smaller and possi-
bly less accurate. Least chipmunks are considered relatively
trap shy, less prone to capture, and thus probably underrep-
resented in trap surveys.
This species appears to be subordinate to congeners and
other ground squirrels when aggressive interactions are in-
volved, although its ability to exploit resources effi ciently
may allow it to successfully compete in some circumstances.
Both T. amoenus and T. minimus occur in the Rocky Moun-
tains, though T. minimus appears to be restricted to the alpine
zone. Experimental removal of T. amoenus results in replace-
ment by T. minimus, indicating that the former is more
dom inant. However, it is also apparent that T. minimus can
survive in both habitats, whereas T. amoenus cannot. Least
chipmunks vocalize frequently and exhibit a diversity of
calls; several types of alarm call are used (fi ve to six), but
detailed analyses of the structure and context of their vocal-
izations are not available. Predators are not reported, pos-
sibly because of this species’ small size, its agility, and its
secretive behavior. Ectoparasites reported from T. minimus
are 2 lice, 1 mite, 4 ticks, 11 fl eas, and 1 fl y (the botfl y [Cutere-
bra]). The least chipmunk can harbor several potential dis-
eases of concern to humans. Although refractory to Colo-
rado tick fever, T. minimus is known to carry the virus that
causes this disease. It also appears to have the potential to
serve as a reservoir host for the bacterium that causes Lyme
disease, although it is unlikely that it hosts the tick that
transmits this bacterium. It is considered highly suscep-
tible to the bacterium (Yersinia pestis) that causes sylvatic
(bubonic) plague. It is also known to serve as a reservoir
host for the tick Ixodes spinipalpis, which is the vector of
Borrelia bissettii, the cause of human granulocytic ehrlich-
iosis, a recently discovered tick-borne disease similar to
Rocky Mountain spotted fever. The least chipmunk is known
to carry strains of the bacteria Bartonella, which are known
human pathogens. Reports of T. minimus from the fossil re-
cord are numerous.general references: Anthony 1928; DeNatale et al. 2002;
Ditto and Frey 2007; Guralnick 2007; Hadley and Wilson
2004a, 2004b; Kosoy et al. 2003; A. W. Linzey and Hammer-
son 2008g; Morris 2005; Root et al. 2001; Vander Haegen et
al. 2002; Verts and Carraway 2001.