Squirrels of the World

354 Urocitellus brunneus

to agriculture. Between 2004 and 2009, however, habitat res-
toration and translocations have resulted in an increase in
population size.

general references: Gavin et al. 1999; Sherman 1989;
Sherman and Runge 2002; Yensen 1991; Yensen and Sher-
man 1997; Yensen, Hammerson, et al. 2008.

Urocitellus canus Merriam, 1898

Merriam’s Ground Squirrel

description: This is a small ground squirrel, dark gray in
color with no visible stripes or spots. The ears are short, and
the tail is short and narrow. The dorsal pelage, the cheeks,
and the hind legs all have a pinkish or buff y wash. The ven-
tral surface is whitish. The tail is gray above and cinnamon
below. U. canus is distinguished from most other ground
squirrels, except U. mollis and U. townsendii, by the absence of
dorsal stripes or spots and its smaller ears. Compared with U.
mollis, U. canus has a smaller and broader skull and rostrum.

size: Female—HB 160.2 mm; T 40.8 mm.
Male—HB 153.3 mm; T 38.4 mm.
Sex not stated—HB 171.1 mm; T 36.3 mm; Mass 154.0 g.

distribution: Merriam’s ground squirrel is found in the
USA, from eastern Oregon to the western bank of the Snake
River in westcentral Idaho and southward to the northeast-

ern and northwestern corners of California and Nevada,

respectively. It is absent from the southeast and northeast

corners of Oregon.

geographic variation: Two subspecies are recognized.

U. c. canus—t hroug hout most of t he species’ ra nge. This sub-

species’ skull and body size are slightly smaller than

those of U. c. vigilis.

U. c. vigilis—from eastern Oregon to the western bank of the

Snake River in westcentral Idaho (USA). It is more hoary

white than U. c. canus.

conservation: IUCN status—least concern. Population

trend—no information.

habitat: Merriam’s ground squirrel occurs in areas of non-

forested desert chaparral (upper Sonoran life zone) in east-

ern Oregon, as well as in the riparian zones, pastures, and

disturbed open areas of the western bank of the Snake

River. Its desert habitat is often associated with big sage-

brush (Artemisia tridentata), western juniper (Juniperus occi-

dentalis), and greasewood (Sarcobatus vermiculatus). U. canus is

often found in conjunction with irrigation ditches and agri-

cultural fi elds, where it can cause signifi cant damage.

natural history: Like many other species in the genus,

U. canus feeds on vegetation, fruits, roots, and seeds, but it

also includes animal material, such as insects, in its diet. U.

c. vigilis in particular is noted for causing damage to alfalfa

fi elds. Population densities are changeable, due to the food

supply, disease, predators, and overwinter survival, but de-

mographic studies are not available. Densities usually vary

annually between about 20 and 50 animals/ha before and

after the young are weaned. U. canus is diurnal, but adults

may be more crepuscular than juveniles. Like other species

Urocitellus canus. Photo courtesy Ronn Altig.

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