Sciurus griseus 55to the dorsum, but it is sometimes darker at the core and has
a frosting of white to silver gray. The ears are a steel or silver
gray and quite prominent, nearly double their relative length
in many other squirrels.
size: Both sexes—HB 265–323 mm; T 240–309 mm; Mass
520–942 g.
distribution: This species is found in central Washing-
ton, western Oregon, and California (USA) to Baja Califor-
nia (México).
geographic variation: Three subspecies are recognized.
S. g. griseus—Washington, Oregon, northern California, and
most of the Sierra Nevada (USA). This form is a silvery
gray color on the dorsum and limbs.
S. g. anthonyi—extreme southern portion of California
(USA), from north of Los Angeles southward into Baja
California (México). This subspecies is intermediate in
coloration.
S. g. nigripes—Coast Range, from San Francisco Bay south-
ward to north of Los Angeles (USA). This form is much
darker on the dorsum and feet, approaching slate gray in
many individuals.
conservation: IUCN status—least concern. Population
trend—no information. S. griseus is listed as a threatened
species in the state of Washington and as sensitive in Ore-
gon (USA).habitat: Western gray squirrels occur in oak-conifer
woodlands and mixed conifer forests on the mesic western
side of the mountains. Open pine (Pinus) forests are fre-
quented on the more xeric eastern side of the mountains.
This species is also found in cities and, occasionally, in nut
orchards, but it does not seem to thrive in such close prox-
imity to humans.natural history: This species is diurnal. Western gray
squirrels are often seen foraging on the ground during all
seasons, and they are less apt to be found moving in the
canopy than most tree squirrels. When in the canopy, this
large-bodied squirrel appears less agile and rarely leaps be-
tween branches, as do other tree squirrels. Males chase a
female through the canopy and across the ground on her
single day of estrus, in an attempt to mate; aggression levels
between males are considerable. The breeding season
ranges from late December to June or July. After a gestation
of about 44–45 days, a litter of one to six is born in a nest
cavity or leaf nest. Cavities may be preferred for rearing off -
spring. Most of the young leave the nest by May, and all
disperse from their natal area. Sexual maturity is reached at
10–11 months of age; however, young females have less suc-
cess in producing a litter than older females. Adult individu-
als are solitary and are not territorial. Home ranges cover
from less than 5 ha for both sexes in some parklands, to 73
ha for males and 22 ha for females elsewhere, with consider-
able overlap between individuals. Males overlap with many
females, especially during the breeding season. Nests are in
large trees within reasonably dense and diverse forest sites.
S. griseus is primarily herbivorous, feeding on the seeds of
oaks (Quercus) and a variety of conifers. Epigeous (aboveg-
round) and hypogeous (underground) fungi are also impor-
tant foods and may make up most of the diet in some forests.
In addition, western gray squirrels will feed on fl owers,
fruits, forbs, sap, and cambium. When disturbed or threat-
ened, S. griseus usually ascends a tree and faces the threat
while fl agging its tail and projecting an alarm call in a series
of moderately pitched “chucks,” often increasing in length
as the end of the series approaches. Major predators include
raptors, bobcats (Lynx rufus), domestic cats, coyotes (Canis
latrans), foxes, domestic dogs, and mustelids. Western gray
squirrels feed on a variety of nut crops and are considered
pests in some areas. This species is hunted outside of the
state of Washington. Major threats to persistence are habi-
Sciurus griseus. Photo courtesy Larry McCombs / Flickr. tat loss and fragmentation, introduced eastern gray squirrels