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Toxic plant blamed for cattle die-off

Larkspur, a poisonous plant, is believed to have killed dozens of cows in the Beartooth Mountains this month. Larkspur, a poisonous plant, is believed to have killed dozens of cows in the Beartooth Mountains this month. Tribune photo by Mark Davis

Dozens of cattle recently died in the Shoshone National Forest along the Beartooth Highway after browsing on larkspur, a toxic plant that grows throughout the West.

Park County Sheriff Scott Steward passed by the scene and, based on his counts from the highway, figured there was a minimum of three dozen dead animals.

“It happened overnight,” Steward said. “Because I was up there on Thursday [Aug. 31] and there was none — and then Friday [Sept. 1] they were dead, laying all over the place.”

The cattle belonged to the Sunlight Ranch.

The sheriff said he regularly sees one or two dead cattle when traveling through the Beartooths, but to see dozens dead overnight, “it was insane,” Steward said.

He said the carcasses were spread along the Beartooth Highway (U.S. Highway 212), starting a mile or so east of its junction with the Chief Joseph Highway (Wyo. Highway 296) and continuing for several miles.

The wet spring is the culprit, according to Dan Tekiela, assistant professor and extension specialist of invasive plant ecology at the University of Wyoming.

“The wet early spring was a real boon for larkspur,” Tekiela said.

The combination of the weather and targeted grazing potentially was a deadly combination this year. As ranchers push cattle into fields, based on the occurrence of larkspur, cows will eat other vegetation — giving larkspur less competition over the years, Tekiela said. Then, a wet spring gives the toxic plant a headstart, making for a rough year for the area cattle industry.

The Park County Weed and Pest Control District declared larkspur a noxious plant this year, making funds available for cost sharing on spraying. The district will cover 50 percent of the cost of spraying in the county and has rental equipment available, district supervisor Josh Shorb said.

“Ranchers need to pre-scout. If the larkspur is in bloom, you’re asking for trouble,” Shorb said. “It’s a native plant and it’s here for the long haul.”

Ashley Duke, Shoshone National Forest north zone recreation director, said the national forest only gets involved in the process if dead livestock present a public safety issue. Carcasses will draw in grizzly bears, so if there is a die-off near trails, campsites or roads, forest employees move in to ensure the cattle are removed.

“Toxin levels are different throughout the year,” Duke said. Larkspur can pop up anywhere in the state, according to Duke. The plant has been responsible for livestock losses in other Western states, too.

There are three types of larkspur: low, plains and tall. While all are toxic, tall larkspur increases in toxicity through the season. While past prime in the fall — devoid of its beautiful blue and purple blooms — the abundant plant is still full of toxins. And this year, larkspur at higher elevations are still in bloom.

According to the U.S. Department of Agriculture, symptoms of larkspur poisoning include general weakness and muscle spasms, as well as abdominal pain and nausea. Eventually, it can lead to respiratory distress, paralysis and death in humans and animals.

The carcasses of cattle that died from eating larkspur were brought up to the Beartooth Highway on Sept. 8 to be hauled away.
Photo courtesy Scott Steward

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