Tamias sibiricus 339and the shoulders of T. s. umbrosus. The head color is
darker and duller.conservation: IUCN status—least concern. Population
trend—stable.habitat: Found in boreal forests across its range, T. sibiricus
is almost exclusively a resident of coniferous forest habitats
(e.g., mixed stands, including Siberian pine [Pinus sibirica]).
In Japan the species is reported from stands dominated by
oak (Quercus).natural history: The Siberian chipmunk is primarily gra-
nivorous, feeding consistently on conifer seeds but also eat-
ing herbaceous plants and animal material, including insects,
bird eggs, nestlings, and mollusks. T. sibiricus is apparently a
signifi cant predator of the dusky warbler (Phylloscopus fusca-
tus); under some circumstances it can infl ict 80–90 percent
mortality on these warblers, and this probably infl uences
nest-site selection by the bird. The Siberian chipmunk is
somewhat arboreal and will, on occasion, nest in stumps and
logs. However it usually constructs relatively simple shallow
burrows that are used for nesting and larder-hoarding food.
The burrow structure diff ers during early and late hiberna-
tion. Early in hibernation, burrows usually consist of a single
nest chamber and a plug that blocks the entrance. Later dur-
ing hibernation, the tunnel is blocked further and one or two
secondary chambers are constructed. In the spring these sec-
ondary chambers are then fi lled by the soil excavated to con-
struct a new tunnel. Each burrow is occupied either by a
single chipmunk or by a mother and her young. Siberian
chipmunks are abundant throughout their range, but littledemographic data is available. T. sibiricus is reported to mi-
grate during years of food shortages. Home ranges reported
for an introduced population in France averaged 1.86 ha for
males and 0.76 ha for females; these chipmunks showed con-
siderable site fi delity over a two-year period and home range
overlap was signifi cant (more than 80%) over one year, but
male home ranges overlapped more with those of females
than with those of other males. Adults enter hibernation be-
fore juveniles, and females do so before males. The onset of
hibernation varies annually and is infl uenced in part by bur-
row and food availability. Females enter estrus for a single
day, usually within a few days after emerging from hiberna-
tion. Distinctive vocalizations, consisting of three calls, are
given during estrus; one is for advertisement, and all three are
involved in courtship. Details from a few observations on
copulation are reported in the literature. Gestation is 30–31
days. Litter sizes average 4.4 (range = 1–8) and 4.7 (range = 2–7)
in two lab studies, and 4.6 (range = 3–6) in the wild in Japan.
One litter per year is produced in the wild, but two are pos-
sible in captivity. This species is not territorial.
In some parts of its range (e.g., Italy), introduced popula-
tions of T. sibiricus may contribute to the decline of the en-
dangered Sciurus vulgaris. In China T. sibiricus appears to be
a reservoir host for Cryptosporidium parva, a protozoan
pathogen of humans and cattle. A minimum of four species
of nematodes are reported from T. sibiricus, but at least one
is from nonnative populations. T. sibiricus can host the bac-
terium Yersinia enterocolitica in Japan, a potential pathogen
that causes yersiniosis in humans. Vision, including the
structure and function of the retina and the optic nerve, has
been studied extensively in T. sibiricus. Probably because it
is maintained easily in captivity, this species is frequently
used for biomedical studies. Primary neoplasia of the liver
has been reported in Siberian chipmunks.general references: Bertolino 2009; Bertolino, Currado,
et al. 2000; Bertolino and Genovesi 2005; Blake 1992; Blake
and Gillett 1988; Ellis and Maxson 1979; Forstmeier and
Weiss 2002, 2004; Gromov et al. 1965; Kaneko and Hashi-
moto 1981; M. Kawamichi 1989, 1996; T. Kawamichi and
Kawamichi 1993; Koh, Wang, et al. 2009; Koh, Zhang, et al.
2010; Levenson et al. 1985; T. Li et al. 2004; Marmet et al.
2009; Matsui et al. 2000; Niethammer and Krapp 1978; Os-
hida and Yoshida 1994; Pisanu et al. 2009; A. T. Smith and
Xie 2008; Tsytsulina, Formozov, Shar, et al. 2008; Vourc’h et
al. 2007.Tamias sibiricus. Photo courtesy David Blank, http://www.animal
diversity.ummz.umich.edu.