278 Marmota caudatawinter and emerge in late spring or early summer from their
burrows. Only 17 percent of females breed during this spe-
cies’ short active season. Gestation is about 30–33 days, after
which a litter of two to six young is born. Weaning is earlier
when food resources are abundant. More than 60 percent of
juveniles die during the fi rst year; 22 percent of this mortal-
ity is due to infanticide by new resident males, which are
apparently trying to avoid providing resources for another
male’s progeny. Juveniles delay dispersal and remain in
their natal group for at least three years. Most of the disper-
sal appears to occur after sexual maturity, when males move
to groups with fewer individuals than their natal group.
Nonjuvenile survival rises in years when food is abundant.
M. caudata is a gregarious species; these marmots live in
large colonies frequently consisting of monogamous pairs,
but there can be groups of seven adult animals plus their
young and yearlings. The home ranges of the social groups
are large, averaging 3.0 ha. Group members will sleep to-
gether and generally behave amicably toward each other.
M. caudata forage for long hours on a variety of legumes,
herbs, grasses, and small shrubs to accumulate subcutane-
ous fat reserves for the winter. Individuals are often seen
basking on rocks or at burrow entrances, or standing on their
haunches surveying their surroundings for potential threats.
Individuals emit complex alarm calls that warn conspecifi cs
about the relative risk of predation, and they use a variety of
less apparent vocalizations in other social contexts. An as-
sortment of large raptors, canids, and felids are frequent
predators. Males and females each scent-mark from orbital
glands, doing so primarily in the vicinity of their burrows;
males are more responsive to novel scents than females. In
some portions of their range, long-tailed marmots are
hunted and trapped for food, pelts, and medicinal purposes;
they are not considered pests, except where they are be-
lieved to compete with livestock for forage.
general references: Blumstein and Arnold 1998; Habibi
2003; T. J. Roberts 1977.
Marmota fl aviventris (Audubon and
Bachman, 1841)
Yellow-B ellied Marmot
description: The dorsal surface of the head is brown to
black, usually with white patches in between the eyes and
the snout, on the sides of the snout, and on the apex of the
lower jaw. The side of the neck is buff to yellow to orange.
The venter is buff to yellow. The feet are buff to brown.
size: Females—Mass 2800 g (1590–3970 g) after hibernation.
Males—Mass 3900 g (2950–5220 g) after hibernation.
Both sexes—HB 470–700 mm; T 130–220 mm.
Males tend to be longer than females.distribution: Yellow-bellied marmots are found from
south ern British Columbia and Alberta (Canada) south to
California, Nevada, southern Utah, and northern New Mex-
ico (USA). There is also an isolated population from north-
eastern Wyoming to western South Dakota (USA).geographic variation: Eleven subspecies are recognized.M. f. fl aviventris—Cascade and northern and central Sierra
Nevada ranges of Oregon and California (USA). The dor-
sal surface is grizzled russet and white. The upper back
has an indistinct buff y mantle. The underparts and feet
are ochraceous.
M. f. avara—throughout the northwestern range. This form
is smaller and paler.
M. f. dacota—endemic to the Black Hills of South Dakota
(USA). This subspecies, while similar to M. f. nosophora,
has redder fur ventrally.
M. f. engelhardti—central to southwestern Utah (USA). This
is a smaller form, with dark red on the upperparts and
feet.
M. f. fortirostris—endemic to the White Mountains on the
California–Nevada border (USA). This subspecies is sim-
ilar to M. f. sierrae, but smaller and paler.