Yellowstone's Northern Range - Greater Yellowstone Science ...

THE NORTHERN RANGE
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were purchased through a cooperative effort of the
Rocky Mountrun Elk Foundation, the U.S. Forest
Service, the Montana Department of Fish, Wildlife
and Parks, and the National Park Service, that
constituted a significant conversion of land use,
from livestock to wildlife grazing.
From 1979 to 1988, elk counts increased
from 10,768 to 19,043. The mild winters of the
1980s, a trend of increasing winter range grassland
production from 1974 through 1981, and
recolonization by elk of winter ranges north of the
park (Dome Mountrun, etc.) all effectively
increased winter carrying capacity for elk, so the
count of 19,043 and the calculated high of around
20,800 in January 1988 should not have been
surprising. Drought, fire, and a winter of normal
severity in 1988-1989 temporarily lowered the
ecological carrying capacity. In the winter of
1988-1989, about 25 percent ofthe elk herd winterkilled
and another 15 percent was harvested by
hunters, so the herd was reduced by about 40
percent. In January 1990, 14,829 elk were counted
on the northern range, including 2,139 on the
newly-acquired Dome Mountain Wildlife Management
Area. Since 1990, counts of the northern elk
herd have ranged between about 16,000 and about
20,000.
The northern Yellowstone elk herd is too
often viewed without reference to the other
greater Yellowstone ecosystem herds, which offer
further proof that nothing unseemly was happening
as the northern herd increased since 1968. In
fact, most of the greater Yellowstone elk and deer
herds, managed under a variety of approaches and
goals. increased during the 19808, responding to
the same favorable weather conditions (and
perhaps other factors) that prevailed on the
northern range (Figure 6.2) (Singer 1991b).
Regionwide, mule deer doubled in number, and elk
increased nearly 40 percent. The increases in the
park's northern herd were reported widely as if
they were something unusual Of somehow "unnatural"
when that one herd was only doing what all the
others were also doing: growing in size as the mild
winter weather conditions allowed.
The inherent variability in these ungulate
herds can hardly be overemphasized. During the
1980s prior to 1988, and during years since 1988,
the summers were unusually wet, with the northern
range experiencing 200 percent of normal precipitation
in some months. The forage produced in
these years allowed the ungulates to increase their
population size year after year (Merrill et a1. 1988,
Singer et a1. 1989). The winters, on the other hand,
were unusually dry, further allowing for high
survival rates in populations that usually were
naturally "culled" by winter mortality. Then, in
1988, not only was there the most severe drought
in a century, resulting in a lower food crop, but also
the fires burned a portion of the ranges, further
reducing forage.
The winter following the fires fmther
compounded the challenge for the animals, as it
was the first in many years with normal snowfall.
In February, three Arctic cold fronts fatally stressed
many animals that had previously benefited from a
series of mild, easy winters (Singer et a1. 1989,
Singer and Schullery 1989, Coughenour and Singer
1996b, Singer and Harter 1996). Many animals
died as a result of this "triple whammy" (forage
reduced by summer drought and further reduced by
burning, and a severe winter). Following the
mortality of elk in 1988-1989, population recovery
was rapid, facilitated by the return of the wet
summers, dry winters, and probably also by the
superior quality and quantity of post-fire forage.
There is a long-standing paradox in the
notion that the northern elk herd is far too numerous
for the range's carrying capacity. Since 1968,
when the elk herd was no longer controlled by
shooting in the park and was allowed to grow to
whatever size it could, the northern range was
somehow able to fuel an increase in the elk
population from less than 5,000 to as high as
20,000, and to mruntain that higher level of elk
population for more than 10 years. All the time
this was happening, alarm was expressed about the
condition of the range with "too many elk" on it.
But these alarms beg a fundamental question: How
could a range that had been characterized as
overgrazed for more than half a century produce so
many elk, year after year? Even if the many
research projects of the past 20 years had not called
into question traditional views of an overgrazed