HELENA — State wildlife officials report that several elk calves died last month after eating what are described as "toxic ornamental plants" in the Bitterroot Valley.

According to Montana Fish, Wildlife and Parks (FWP), at least five elk calves were killed in mid-January in the Florence area after eating what's been identified as in necropsies as "high quantities of toxic Japanese yew (Taxus cuspidata)."

An examination of properties in the area revealed several of the plants that had been "browsed". FWP reports the homeowner voluntarily removed the plants.  

 Japanese yew, an evergreen, tree-like shrub native to East Asia, is a popular landscaping plant, commonly planted around homes and walkways.

"Because it's not native to the area, animals aren't familiar enough with the plant to know or teach their young that it's toxic," said area biologist Rebecca Mowry. "Even a small amount can kill them, and yearlings are especially susceptible."

According to FWP Wildlife Veterinarian Jennifer, an amount that weighs less than 1% of an elk’s body weight is enough to cause death.

“The elk we necropsied here at the wildlife health lab had a large amount of yew – leaves, stems and seeds – in it’s rumen,” Ramsey said. “Yew toxicity often causes sudden death, commonly within two to four hours after ingestion.”

Additional information from Montana Fish, Wildlife and Parks: