Mountain Wildlife - Mountain Geography: Physical and Human Dimensions - page 422

presence of snow for insulation. Some species (e.g., lemmings) huddle together in sub-
terranean nests and share body heat, while others (e.g., pikas) are strictly solitary. Chip-
munks and hamsters have the ability to become torpid for intermittent periods. This in-
termediate level of hibernation is a very useful adaptation, but they must occasionally
awake and feed between periods of slumber. Other species such as the pocket gopher,
deer mice, and pikas do not have this ability and must remain active throughout winter
(Hoffmann 1974).
The pika is a particularly interesting little creature (Fig. 8.8). Pikas live in rocky hab-
itats such as talus slopes and blockfields located near or above timberline. They are
strongly territorial, with a definite spacing between their dens (Barash 1973; Smith
1974, 1978). Much of their summer activity consists of gathering twigs, which they de-
posit into a central “hay pile,” for winter food. The exact winter behavior of pikas is
unknown. They apparently do not build up stores of body fat or become torpid, so they
depend heavily on their hay piles. Their dens are separated from the hay piles, so they
must come up to the surface to feed, while other animals such as chipmunks use their
winter supply of seeds as a bed and have only to turn their heads to feed. Another curi-
ous dietary characteristic of the pika is its tendency to reingest its own fecal matter.
Like other members of the rabbit family, pikas excrete two kinds of feces. One is the
familiar pellets, which are not reingested; the other is an elongated dark mass called
“night” or “soft” feces, which is thought to come from excavation of a pouch in the large
intestine. This material contains a high concentration of proteins and vitamins and its
ingestion adds significantly to the pikas' nutrient intake (Johnson and Maxwell 1966).
The small mammals that continue foraging during the winter include the pocket
gopher ( Thomomys spp.), some voles ( Microtus spp.), shrews ( Sorex spp.), and weasels
( Mustela spp.). Apart from the shrews and weasels, these all depend on seeds, roots,
and other vegetable matter for food. The critical factor for their survival is the presence
of snow, since they do not have adequate insulation to protect themselves from ex-
tremely low temperatures. Even when snow is present, temperatures remain near the
freezing mark and conditions are suboptimal. The animals compensate by constructing
warm nests, clustering together to share body heat, or, in the case of the weasel, by
maintaining a high level of metabolism (Brown and Lasiewski 1972).
The pocket gopher is a good example of a small mammal that continues foraging
throughout winter. These little creatures have well-developed front claws for digging
and spend most of their time below ground or under snow. They are solitary and, during
summer, each maintains its own underground burrow system, harvesting the plant roots
that extend into the tunnels (Aldous 1951). During winter, however, the pocket gopher
moves freely above the ground, under the protection of a deep snow cover, and harvests
the surface vegetation. While most animals deposit their excavated material in mounds,
the pocket gopher carries its refuse upward and stuffs it into snow tunnels. These are
frequently quite extensive and, after the snow melts in spring, the material is deposited
on the ground surface in a curious pattern of interwoven soil ropes.
There has been considerable concern over the question of whether the pocket gopher
increases erosion through burrowing. While the close browsing of grasses and sedges
under the snow may do temporary damage, it does not kill the plants. The annual de-
position of fresh, loose soil on the surface may also result in some loss, but there is no
evidence of major erosion (Ellison 1946; Stoecker 1976). In fact, it is generally believed