Featured video filmed by Phil Takatsuno Yellowston Media from the DVD "Wildlife of Yellowstone" |
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Elk - National Park Service
Elk
(Cervus elaphus) are the most abundant large mammal found
in Yellowstone; paleontological evidence confirms their continuous
presence for at least 1,000 years. Yellowstone National Park was
established in 1872, when market hunting of all large grazing
animals was rampant. Not until after 1886, when the U.S. Army
was called in to protect the park and wildlife slaughter was brought
under control, did the large animals increase in number.
More
than 30,000 elk from 7-8 different herds summer in Yellowstone
and approximately 15,000 to 22,000 winter in the park.
The subspecies of elk that lives here are found from Arizona to
northern Canada along the Rocky Mountain chain; other species
of elk were historically distributed from coast to coast, but
disappeared from the eastern United States in the early 1800s.
Some other subspecies of elk still occupy coastal regions of California,
Washington, and Oregon. Elk are the second largest member of the
deer family (moose are larger). Adult males, or bulls, range upwards
of 700 pounds while females, or cows, average 500-525 pounds.
Their coats are reddish brown with heavy, darker-colored manes
and a distinct yellowish rump patch.
Bulls
grow antlers annually from the time they are nearly one year old.
When mature, a bull’s "rack" may have 6 to 8 points
or tines on each side and weigh more than 30 pounds. The antlers
are usually shed in March or April, and begin regrowing in May,
when the bony growth is nourished by blood vessels and covered
by furry-looking "velvet." Antler growth ceases each
year by August, when the velvet dries up and bulls begin to scrape
it off by rubbing against trees, in preparation for the autumn
mating season or rut. A bull may gather 20-30 cows into his harem
during the mating season, often clashing or locking antlers with
another mature male for the privilege of dominating the herd group.
By November, mating season ends and elk generally move to their
winter ranges. Calves weighing 25-40 pounds are born in late May
or early June.
Climate
is the most important factor affecting the size and distribution
of elk herds here. Nearly the whole park - approximately 2.2 million
acres - provides summer range for elk. However, winter snowfalls
force elk and other ungulates to leave the greater part of the
park. Only the northern, lower-elevation portion of Yellowstone,
where temperatures are more moderate and snowfall less than in
the park interior, can support large numbers of wintering elk.
Annual precipitation, which occurs mostly as snow, averages as
high as 75" in the southern, high-mountain plateaus of the
park; minimum temperatures there are often well below 0° F, and
have been as low as -66° F. In contrast, most of the northern
range averages less than 30" of precipitation annually, and
winter temperatures are considerably warmer.
The
Overgrazing Controversy
 National
attention has been focused on Yellowstone's northern elk winter
range since the early 1930s. Scientists and managers then believed
that grazing and drought in the early part of the century had
reduced the range's carrying capacity, and that twice as many
elk were on the range in 1932 as existed in 1914. From 1935 to
1968, elk, pronghorn, and bison numbers were artificially controlled
by shooting or trapping and removal by park rangers. Then in the
1960s, based on new studies that suggested ungulate populations
could possibly be self-regulating, elk reductions were discontinued
in the park. The belief that elk grazing was damaging to northern
range vegetation and that grazing accelerates erosion, although
not supported by research data and analysis, has continued to
the present. Studies of the northern elk winter range began in
the 1960s and revealed no clear evidence of range overuse (Houston
1982). More recent studies conclude that sagebrush grasslands
of Yellowstone's northern winter range are not overgrazed
(Singer and Bishop 1990). In fact, plant production was enhanced
by ungulate grazing in all but drought years. Protein content
of grasses, yearly growth of big sagebrush, and seedling establishment
of sagebrush were all enhanced by ungulate grazing. Neither reduction
in root biomass nor an increase in dead bunchgrass clumps was
observed. However, many questions remain concerning the condition
of riparian zones and associated shrubby vegetation; the park
hopes to conduct additional studies on aspen and willows and their
relationship to ungulates on the northern range.
Two
reports were made available in 1997, discussing at length the
issue of grazing levels and other influences on Yellowstone's
northern range. Yellowstone's Northern Range: Complexity and
Change in a Wildland Ecosystem discusses the history of research
and management in northern Yellowstone, home to one of the world's
largest herds of elk and long the subject of controversy. Effects
of Grazing by Wild Ungulates in Yellowstone National Park contains
22 technical publications summarizing recent research studies
that have been peer-reviewed by scientists. Much of the research
was completed by scientists from agencies other than the National
Park Service, by independent contractors, and by scientists from
universities located across the United States. For a copy of either
report, contact the Yellowstone Center for Resources, Box 168,
Yellowstone NP, Wyoming 82190, or call (307)344-2203.
Other
Influences on Yellowstone's Elk Populations
Over-winter
calf mortality, yearling mortality, and adult bull mortality all
increase with higher elk population densities. Studies show that
summer predation by grizzly bears, coyotes, black bears, and golden
eagles takes an average of 32% of the northern range elk calves
each year. Mountain lions prey upon elk, as do hunters north of
the park (taking about 10% of the northern herd annually through
the 1980s).
Gray
wolves, eliminated from the park by the 1930s, are being restored,
but not because park managers think the wolves will "control"
the number of elk. Instead, 15 North American wolf experts predicted
that 100 wolves in Yellowstone would reduce the elk by less than
20%, 10 years after reintroduction. Computer modeling of population
dynamics on the northern winter range predicts that 75 wolves
would kill 1,000 elk per winter, but that elk would be able to
maintain their populations under this level of predation, and
with only a slight decrease in hunter harvest. Since the restoration
of wolves to Yellowstone began in January 1995, scientists have
begun to document the effects of wolves on elk and other species.
Wolves are preying predominantly on elk, as expected. They have
also occasionally preyed upon moose, bison, deer, and even one
pronghorn antelope.
The
carrying capacity of the northern winter range increased in the
1980s because elk colonized new winter range in and north of the
park, wet summers resulted in better plant production, winters
were mild, and the fires of 1988 opened forests allowing more
ground cover to grow. Since 1985, more than 11,000 acres of elk
winter range have been purchased by the State of Montana and the
U.S. Forest Service north of the park, increasing elk carrying
capacity and reducing conflicts between native wildlife and agriculture.
The
Madison-Firehole Herd
The
Madison-Firehole elk herd has been the focus of research by Dr.
Bob Garrott of Montana State University since November 1991. This
herd numbers from 650-850, and is believed to winter almost entirely
within Yellowstone Park. The population appears to be naturally
regulated to a degree not found in other, human-hunted elk herds.
The information resulting from this research is useful in comparing
unhunted and hunted elk populations. Researchers examined the
effects of environmental variability on ungulate reproduction
and survival. Researchers also examined elk use of areas burned
in the wildfires of 1988. Observations indicated that elk have
made more than casual use of burned trees; tests showed that fires
altered the chemical composition of lodgepole pine bark, making
it more digestible and of higher protein content than live bark.
While the burned bark was not the highest quality forage for elk,
it is comparable to other low quality browse species. The researchers
speculated that elk select burned bark because it is readily available
above the snow cover in winter.
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