Sagebrush - Mountains and Plains: The Ecology of Wyoming Landscapes - page 128

large herds that graze the rangeland excessively. in 2012
the Bureau of Land Management estimated there were
about 3,500 horses in Wyoming. 91
to maintain the feral horse population at appropriate
levels, horses are rounded up periodically and offered
for adoption or for relocation to sanctuaries—the only
option, by federal law, for adjusting horse numbers to
habitat conditions. this method of control has been
questioned, because the number of people desiring
the horses can be insufficient to keep the population
in check. Research is under way to develop a practical
method of birth control, but some observers have con-
cluded that more drastic measures are needed. Despite
the damage they can cause to rangelands, many people
enjoy seeing a herd of feral horses loping across the
plains, a vignette of the western frontier.

national incentives for energy independence that may
result in further loss and fragmentation of sagebrush
habitat. Also, fire commonly has been prescribed for
increasing forage availability for livestock. indirectly,
climate change could become a factor if precipitation
patterns change so that deep-soil recharge during spring
snowmelt is not adequate to support big sagebrush. All
such factors interact in troublesome ways, to the point
that the sagebrush steppe is arguably an endangered
ecosystem. 93
of all the declining sagebrush-dependent species,
the greater sage-grouse has received the most attention
(fig. 7.17)—in part because it has a curious courtship
display in the spring. More importantly, the U.S. Fish
and Wildlife Service concluded in 2010 that this bird
warrants protection under the endangered Species Act.
considering the adverse socioeconomic consequences
of listing the sage-grouse (because the energy and
agricultural industries would be affected), conserving
the habitat for this species has become a priority for
many sectors of society. the natural Resources con-
servation Service, part of the U.S. Department of Agri-
culture, now has a sage-grouse initiative; and the state
of Wyoming has identified core areas that are critical
for the maintenance of sage-grouse populations (see
chapter 18). 94
there are several species of grouse in north America,
each adapted to different ecosystems—an evolutionary
process known as adaptive radiation that results in less
competition from closely related species. not surpris-
ingly, the large land area occupied by sagebrush pro-
vided a niche for one of them, the greater sage-grouse. 95
through evolution, this bird acquired adaptations that
enable it to eat sagebrush leaves, along with insects and
forbs. For protection from predators, including ravens,
coyotes, and eagles, birds of all ages have color pat-
terns that provide camouflage as they hide under the
shrubs and grasses. Moreover, the sage-grouse are large
(the largest grouse on the continent), which is adaptive
for the often cold environment they occupy. the birds
range over areas up to 30 miles across during the year,
but return faithfully to specific places known as leks for
courtship and reproduction. 96 Breeding adults do not
readily adopt or develop new leks, and they avoid using
leks close to roads with considerable traffic at the time

Disturbing Trends in Sagebrush-Dependent
Animals: Greater Sage-Grouse

considering how much of the West is dominated by
sagebrush, it should not be a surprise that some ani-
mals require this habitat, most notably, pygmy rabbit;
sagebrush vole; and various birds, including Brewer's
sparrow, sage sparrow, sage thrasher, and greater sage-
grouse. 92 other species are common in sagebrush eco-
systems, though they seem to survive in other habitats
as well, for example, coyote, pronghorn, and mule deer.
More than 200 species of vertebrates are associated with
big sagebrush in one manner or another.
Since the 1990s, the abundance of sagebrush-
dependent species has been declining because of
habitat loss caused by various factors, including too-
frequent fires; inappropriate livestock grazing in some
places; and habitat fragmentation stemming from road
building, plowing, the construction of homes in rural
subdivisions, wind farms, and the extraction of oil, gas,
coal, and uranium. Anything causing a decline in both
shrub and herbaceous plant cover could lead to less
food availability and less protection from predators for
sagebrush-dependent species. As the remaining tracts of
sagebrush steppe become smaller, the impacts of distur-
bances have become significantly greater.
Reversing such trends is one of the most formid-
able challenges facing land managers today. there are