Grasslands - Mountains and Plains: The Ecology of Wyoming Landscapes - page 101

Fig. 6.12. More than 100 species of
grasshoppers are found in Wyoming.
Most are adapted for the grasslands and
shrublands in the lowlands, but some
species occur in the alpine tundra. this
one, known as the flambellate grasshop-
per ( Melanoplus occidentalis ), is common
in grasslands. it eats mostly forbs but
also grasses, seeds, and dying or dead
arthropods. Photo by Scott Schell.

or a measure of each.” 67 Favorable conditions for grass-
hopper population outbreaks have also been attributed
to heavy grazing, whether by bison or livestock. 68 Some
of the most interesting and complex ecological ques-
tions pertain to the population dynamics of insects.
the amount of energy that flows to grasshoppers can
be small or large. in northern colorado they consume
less than 0.5 percent of the plant growth during years
with normal population sizes, but 63 percent of the
forage is eaten in outbreak years, with about 20 grass-
hoppers per square yard. 69 notably, the apparent veg-
etation damage is not a good measure of the amount
actually eaten by grasshoppers, as they cut up to 25
times more forage than they eat—leaving considerable
detritus on the soil surface.
in 1941 B. W. Allred described the effects of grass-
hoppers in the Powder River Basin during the 1930s
drought, writing that there were 50-100 per square foot
and that they “destroyed all edible vegetation.” 70 Much
earlier, in 1864, General Alfred Sully wrote, “the only
thing spoken about here [Montana] is the grasshopper.
they are awful. they actually have eaten holes in my
wagon covers and in the tarpaulins that cover my stores.”
curiously, some areas are not affected even during the
worst outbreak years, which illustrates another way that
disturbances can cause patchiness in landscapes. 71
For many years, ranchers and scientists have worked
toward the goal of minimizing economic losses caused

by grasshoppers when their population sizes are high
over large areas. the costs of the various control mea-
sures were justified, in part, by the expectation that they
would keep the population down for several years. that
may be true in some areas, but a recent study concluded
there is little basis for prorating the benefits of con-
trol beyond the year of treatment and that managing
grasslands in ways that conserve the natural predators
of grasshoppers is likely to be a more sound approach,
ecologically and economically. 72
All Wyoming grasshoppers are native and, like bark
beetles in mountain forests, are integral components of
the grassland ecosystem. curiously, the most notorious
grasshopper in the region, the Rocky Mountain locust,
became extinct in the early 1900s. From time to time
this locust swarmed over hundreds of square miles,
forming virtual clouds that consumed crops and native
plants alike. Plagues of flightless Mormon crickets do
much the same, as do other kinds of grasshoppers. How-
ever, their swarms are not as large as those of the now-
extinct Rocky Mountain locust. 73

Prairie Dogs and Other Burrowing Animals

Burrowing animals can cause prominent changes
in grasslands and mountain meadows. For example,
pocket gopher mounds sometimes cover 25 percent of
the soil surface. 74 Predatory skunks and badgers search-