Big Horn Sheep

A bighorn sheep nibbles on a branch along the Yellowstone River near Gardiner on Jan. 7, 2010.

The Upper Yellowstone bighorn sheep herd has seen at least 31 members die since December, most likely from pneumonia.

In mid-December, Montana Fish, Wildlife & Parks reported that 10 wild sheep had died, but they were mostly lambs.

The Upper Yellowstone herd roams an area from Gardiner north to the Tom Miner Basin and had about 130 members in two groups prior to December, said FWP Region 3 chief biologist Howard Burt.

In the month since, biologists have removed an additional 21 bighorn sheep carcasses. Most of the herd’s lambs have died.

Burt said the carcasses are still being tested, so the causes of death are unknown. But biologists expect to find the bacteria responsible for pneumonia.

Herds in the area have suffered small bouts of pneumonia in the past, and a few animals, mostly lambs, have died almost every year.

But this year, the dead animals were all ages, prompting a greater level of concern.

So far, the herd inside Yellowstone National Park appears to have remained healthy.

Pneumonia can be deadly to bighorn sheep, and large die-offs have been documented throughout the West. Often, wild sheep come into contact with domestic sheep prior to the die-offs.

The same bacteria that poses little problem for domestic sheep can be lethal to wild sheep.

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