The Black Hills, Bear Lodge Mountains, and Devils Tower - Mountains and Plains: The Ecology of Wyoming Landscapes - page 279

susceptible to predation, simply because the uneaten
plants provide more cover for stalking predators. if this
happens, the colony could be reduced in size, whether
from predation or because some of the rodents move
to places where more of the vegetation is palatable and
easily clipped. Horehound is a robust plant; clipping it
over large areas by prairie dogs consumes a considerable
amount of their energy.
Wind cave national Park is one of two locations in
the area with sufficiently large prairie dog colonies to
support black-footed ferrets; the other is about 50 miles
to the east, in Badlands national Park and the adjacent
conata Basin in Buffalo Gap national Grassland. the
ferret population at Wind cave has been fairly stable
in recent years, with about 50 animals in 2011. 48 if the
prairie dog population drops because of insufficient food
or other factors (such as sylvatic plague or canine dis-
temper), or because of increased predation by other car-
nivores, then the ferret population will decline as well . 49
the number of prairie dogs is difficult to estimate,
but it is relatively easy to determine the aerial extent
of active colonies. notably, the size of the colonies at
Wind cave national Park has been observed to fluctuate
with weather conditions, expanding during relatively
dry periods. 50 Prairie dogs concentrating in smaller
areas during wet years—so they can clip the taller veg-
etation sufficiently to reduce predation—could explain
this pattern. An alternative, untested hypothesis is that
the number of prairie dogs, rather than their extent,
declines during wet periods because of more effective
predation during years when the plant cover is higher—
which facilitates stalking by predators (fig. 16.13).
considering that climate warming could lead to more
frequent droughts, prairie dogs may expand into larger
areas of short vegetation—assuming sufficient food is
available and predation pressure does not increase as
well (see chapter 6).
Bison and pronghorn populations are prominent
grazers in Wind cave national Park, spending much of
their time in the Red Valley portion of the park, where
mixed-grass prairie is common. Both species are often
seen grazing on prairie dog towns, most likely because
they find more nutritious forage there (see chapter 6). 51
Pronghorn and bison population sizes in the park cur-
rently are thought to be appropriate for the available
rangeland, but, with the threat of increased drought

Fig. 16.12. the dark area in this prairie dog town, located in
Wind cave national Park, was caused by an herbicide applied
the previous summer for the purpose of removing white hore-
hound, an introduced invasive plant that prairie dogs do not
eat. this photo was taken June 14, 2013. Managers anticipate
that native species will become re-established where such
control measures are taken, though the success of this treat-
ment remains to be seen. See text for discussion of how white
horehound is thought to affect the animals adversely. there
are numerous prairie dog colonies in the park that do not yet
have horehound, as illustrated in fig. 16.13.

(fig. 16.12). thus, prairie dogs—along with bison, elk,
and pronghorn—feed primarily on the native species,
thereby favoring the spread of horehound. Unless the
prairie dogs develop a taste for horehound, the animals
will suffer as their native food supply is reduced. indi-
rectly, this could have detrimental effects on the endan-
gered black-footed ferret that was reintroduced to Wind
cave national Park in 2007, not to mention the other
species that depend on prairie dogs and their burrows
(see chapter 6). Moreover, if the horehound is not eaten
or readily clipped by the prairie dogs—or removed by
park managers—the prairie dogs may become more