FAMILY SCIURIDAE Squirrels & allies
Revised edition (August 2009)
earlier versions of this web page had errors
Chipmunks are small striped squirrels in the genus Tamias. Except for one species in northeast Asia, they are found only in North America. All chipmunks have facial stripes.
most places there is only one species of chipmunk, so a starting point
for anyone is to learn their local species. Where I live in Monterey
Co., California, the only species is Merriam's Chipmunk
(above & right). It is a darkish chipmunk with a pattern of
blackish and light gray stripes, and a dark tail without whitish. Some
other chipmunks have crisper black-and-white striped patterns,
including the one and only species in Asia, Siberian Chipmunk (below).
My local species — Merriam's Chipmunk
— ranges through the foothills of central and southern California. It
particularly like chaparral areas and scurries around on branches and
logs. It has a loud, fast alarm call; a series is fast chips. When it
stops, it sways its tail slowly (Reid 2006). Body color, voice,
behavior, and habitat all help to identify chipmunks, but range is most
important. There are no "vagrant" chipmunks. You must know what
chipmunk is in range to make an identification.
I am not an expert on chipmunks. I am learning as I go. In reviewing
these pages in August 2009, I found at least 4 misidentified photos. I
have fixed those, but it is possible that other information or photos
here are wrong. For the moment, the revised information appears
accurate to me, but it has not been reviewed by experts.
Throughout most of eastern North America there is only one species: Eastern Chipmunk
(left). It inhabits forests, scrub, and suburban areas; makes elaborate
burrows; and hibernates in winter. It commonly visits bird feeders. It
has striking black-and-white side stripes but that they do not go
across the rump to the base of the tail. The only other species found
east of the Rockies — in the north woods east to Ontario and Michigan —
and also widely in the Great Basin, is Least Chipmunk
(below). It is grayish and very small. Its stripes go across the rump.
It has a proportionately longer tail than other species, and carries
its tail high when running.
a birder, I put off learning chipmunks for a long time. I had a job in
college skinning birds and mammals for the taxidermy collection at my
small rural school. When I was taught to skin chipmunks and squirrels I
learned that one must look for and locate the bacula — the penis bone —
on all males, and tie it to the label on the specimen. It sounded very
weird to me at the time, and it still sounds pretty strange today (and
no, I'm not making this up). Indeed, if you read Ingles (1965) seminal
book on Pacific coast mammals he has a whole appendix on "technique for
preparing and preserving bacula" and a page of drawings comparing the
bacula of chipmunks. Believe me, it is pretty hard to look for the
bacula of chipmunks in the field! [... and in some species the female
genital bones — baubellum — are also distinctive.]
The first thing is to recognize that a chipmunk is different from the only squirrel that is similar, Golden-mantled Ground-Squirrel
(right). That colorful squirrel is widespread in wooded open country
throughout mountainous western North America. Although the
Golden-mantled Ground-Squirrel has black-and-white body stripes, as do
chipmunks, it lacks any stripes on the face. It is not a chipmunk, but is in a genus (Spermophilus)with many other ground-squirrels.
I started working on this web page in 2001, I had unlabelled slides of
chipmunks in my files. Using the literature that I had at the time, it
was very difficult to separate the species of chipmunk. I hoped that
putting this page together would help me learn something. It did.
Not a chipmunk!
There are now three good field guides that cover North American chipmunks very well:
- Squirrels of the West by Tamara Hartson (1999), in the Lone Pine series,
- Mammals of North America in the Peterson Field Guide series (2006), by Fiona A. Reid, and
- Mammals of North America in the Kaufman Focus Guide series (2004), by Nora & Rick Bowers & Ken Kaufman.
Even so, sometimes these field guides disagree.
is in the Sierra Nevada and Cascade mountain chains that chipmunks
become a major challenge, especially in California. In the central
Sierra, nine species are zonally distributed from Merriam's Chipmunk in
the foothill chaparral to Alpine Chipmunk T. alpinus in the talus slopes up near tree level to Panamint Chipmunk T. panamintinus
of pinyon-juniper woodlands east of the divide. Ingles (1965) explains
that chipmunks illustrate both the biological principle of Gloger's
Rule — mammal species are more heavily pigmented in more humid areas —
and that they have evolved patterns best suited to their habitat. Thus
Merriam's Chipmunk, which lives in dense chaparral where the shadows
are not sharply defined, has dingy stripes. Likewise Alpine Chipmunk,
which exists in open talus slopes, has poorly demarcated stripes. But
other species (Least, Lodgepole, Yellow-pine, Panamint chipmunks) that
"inhabit sunlit open forests where light-bathed twigs cast dark
shadows" have well-defined light and dark stripes. This character is
illustrated by this chipmunk (left) at the base of a huge Giant
Sequoia; note how bright the white stripes appear in the dappled light
of the understory. This photo may be inadequate for identification but
it does illustrate this principle.
Johnson (1943) there can be more variation in the coloration of a
single chipmunk over the course of a year that there is between
species. The pelage can be different in summer than in winter. Sutton
(1962) showed differences in chromosomes and some taxonomic changes
have been adopted largely on genetic grounds. All of these points make
for discouraging reading when thinking about field identification in
Now, however, authors using criteria
developed in birding, and these have helped to sort out many of the
problems. I have photos of a few species that we can use to compare.
Let's start in open habitats: at high elevation or in scrub, and away
from the dense forests, with Least Chipmunk (below left) and Alpine Chipmunk (below right).
(above left) is the common small chipmunk of sagebrush below the
pinyon/juniper zone. The range extends across the entire Great Basin
(it also occurs across much of Canada, and we compared it to Eastern
Chipmunk above). Because of its wide range and variety of habitats it
is the most variable of all chipmunks, but it is also the smallest and
has very short ears. It is said that where its range overlaps other
species it is dominated by larger chipmunks and therefore restricted to
sage and brush habitats. It has much gray to the shoulders and rump,
and the striping pattern is sharp. It often runs with its slim tail
held straight up. Its tail is essentially as long as the rest of its
Alpine Chipmunk (above right) is also small, rather like the Least, but has less distinct stripes (not nearly so black-and-white), has a shorter tail (not as long as its body), and has longer and more pointed ears.
It does have a distinct outer stripe on the body and essentially lacks
the orangeish sides of Lodgepole Chipmunk (instead, the stripes
themselves can be orangey-brown, as on this individual). [Uinta
Chipmunk T. umbrinus of the eastern Sierra and isolated Great
Basin mountains lacks the dark outer stripe but has subdued orangeish
sides.] Alpine Chipmunk is usually found above 8,000' elevation, or
even above 9,000' in the Yosemite Sierra (Ingles 1965, Harris 1982). It
likes talus slopes or meadows at or above timberline.
all chipmunks that live where it snows in winter, these species
hibernate underground. Least, like most chipmunks, does not put on a
layer of fat to hibernate, so it will awake on sunny winter days to
forage from seeds. Alpine does put on a layer of fat, and thus sleeps
from mid-autumn well into spring (Hartson 1999).
|Now let's compare two more colorful chipmunks of Sierran forests: Yellow-pine (top and bottom left), and Lodgepole Chipmunk (bottom right):
of these are small chipmunks, but not as tiny as Least or Alpine. The
sides of both are rather bright orange, contrasting with the white
outer body stripes, but there is no outer dark stripe on Lodgepole,
whereas there is a dark outer border on Yellow-pine. Further,
Yellow-pine has orange color up into the shoulder and lower part of the
face, and even the lower facial stripe is orangeish-brown. The facial
stripes of Lodgepole are crisply black-and-white. Both have a white
patch behind the ear; both have gray atop the head and muzzle; and both
have medium-length ears.
The names —
Yellow-pine and Lodgepole — describe the typical forest habitats of
each species [e.g., Lodgepole is higher in elevation, in general], but
both can occur in a broader range of habitats than their namesake
woods. Yellow-pine Chipmunk has a wide range from southern British
Columbia through northern California, and reaches its southern limit
around Lake Tahoe. Here its range overlaps with Lodgepole, but the
latter is almost entirely a California endemic, down the Sierra Nevada
from Plumas County south to the Transverse Ranges of southern
are diurnal mammals and hibernate in cold weather. They have internal
cheek patches for carrying food. Unlike most ground-squirrels which
store fat for energy during dormant periods, chipmunks have large
underground caches of food the the occasional periods of waking and for
use in early spring in areas still covered by snow. Seeds and fruits
constitute most of their diet although the Least Chipmunk eats a fair
amount of insects and even lizards (Ingles (1965).
chipmunks are not easy to identify to species. One must consider range
and habitat, of course, but also size, ear length, body color, pattern
of stripes, and tail length and color. In some areas, vocalizations are
important. Some of those issues are examined on the next page.
PHOTOS: The top photo of Merriam's Chipmunk Tamias merriami
was at Cone Peak, Monterey Co., California, on 7 Oct 2003; the second
shot was China Camp, Los Padres Nat'l Forest, Monterey Co., in April
1984. The Siberian Chipmunk T. sibiricus was at Oo, Buryatia, in SE Siberia, in July 1984. The Eastern Chipmunk Tamias striatus was at Mt. Hollyoak, Massachusetts, on 24 June 2007. The Least Chipmunk T. minimus was at Devils Tower Nat'l Monument, Wyoming, 15 June 1998. The Golden-mantled Ground-Squirrel Spermophilus lateralis
was at Olmstead Pt., Yosemite Nat'l Park, 11 July 1981. The chipmunk in
the shadows at Grant Grove, Kings Canyon Nat'l Park, in June 1997, is
probably the Lodgepole Chipmunk T. speciosus. The Alpine Chipmunk T. alpinus was above Saddlebag Lake, Mono Co., California, on12 Aug 2009. The top Yellow-pine Chipmunk T. amoenus was at Taylor Creek, on the edge of Lake Tahoe, El Dorado Co., California, on 14 Aug 2006; the second Yellow-pine was at Willow Lake, Plumas Co., California, on 23 July 2007. The Lodgepole Chipmunk T. speciosus was at Devils Postpile Nat'l Monument, Madera Co., California, on 19 Aug 1998. All photos © Don Roberson, except that of Tamias sibiricus provided by Vladimir Dinets, used with his permission; all rights reserved.
Bowers, N., R. Bowers, and K. Kaufman. 2004. Mammals of North America. Kaufman Focus Guide. Houghton Mifflin, Boston.
Harris, J.H. 1982. Mammals of the Mono Lake-Tioga Pass Region. Kutsavi Books, Lee Vining, CA.
Hartson, T. 1999. Squirrels of the West. Lone Pine Field Guide. Lone Pine Publ., Edmonton, AB.
Ingles, L.G. 1965. Mammals of the Pacific States. Stanford Univ. Press, Stanford, CA.
Jameson, E.W., Jr., and H.J. Peeters. 1988. California Mammals. Univ. of Calif. Press, Berkeley.
Johnson, D.H. 1943. Systematic review of the chipmunks (genus Eutamias) of California. Univ. Cal. Publ. Zool. 48: 63-148.
Reid, F.A. 2006. Mammals of North America. Peterson Field Guides. Houghton Mifflin, Boston.
D.A. 1962. "Chromosomes of some Sciuridae," abstract of paper given
before the Western Society of Naturalists, San Jose, CA, cited in
Sutton, D. A. 1987. Analysis of Pacific coast Townsend's Chipmunks (Rodentia: Sciuridae). Southwestern Naturalist 32: 371-376.
Sutton, D. A., and C. F. Nadler. 1974. Systematic revision of three Townsend's Chipmunks (Eutamias townsendii). Southwestern Naturalist 19: 199-211.
Wilson, D. E., and S. Ruff. 1999. The Smithsonian Book of North American Mammals. Smithsonian Instit. Press, Washington, D. C.
Page created 7-23 June 2001, revised 5-6 July 2008 and revised again 18 Aug 2009