| Yellowstone Bison Slaughter
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| News
Article 3/24/04 |
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| Poison
gas kills five bison in Yellowstone
By SCOTT McMILLION, Bozeman Daily Chronicle Staff Writer
March 24, 2004
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Five
bison have died after being exposed to poison gas in a
geyser basin in Yellowstone National Park.
The dead animals were discovered March 10 in the Norris
Geyser Basin. They probably had been dead about a week,
the National Park Service announced Tuesday.
The two adults, two calves and a yearling, were found
"lying on their sides, with their feet perpendicular
to their bodies," the announcement said. "The
unusual position of the carcasses indicates the bison
died very rapidly, as a group."
The bison probably succumbed to a combination of hydrogen
sulfide and carbon dioxide emitted by nearby thermal features.
Park scientists, lead by geologist Henry Heasler, surmise
the animals were grazing alongside the Gibbon River during
an unusually cold and still night about March 1, when
a cold front passed through the area.
The weather probably caused the steam and toxic gases
to remain close to the ground and concentrate in lethal
doses.
Hydrogen sulfide and carbon dioxide can accumulate in
low areas when the air is still because they are denser
than air.
Some of the nearby vents spewed gas that was more than
200 parts per million hydrogen sulfide, which is commonly
known as "rotten egg" gas because of its distinct
smell.
Humans can easily detect the gas at levels as low as one
part per million and "are able to escape an area
well before it reaches a toxic level," the Park Service
said.
"The fairly constant wind in the Yellowstone area
dilutes and disperses gases so that it would be almost
unheard of for a park visitor to be overcome by toxic
fumes as the bison were," the Park Service said.
Still, animals sometimes fall to the toxic gases.
There is an area known as Death Gulch in the upper Lamar
River Valley where dead animals were found in the 19th
century.
In 1899, a geologist found six bears, an elk and several
rodents and other small creatures there. Another biologist
found seven dead bears there in 1899.
Other researchers have noted the presence of deadly gases
in Yellowstone over the years.
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