''Poison cases are very hard to make, especially when it's showing up mostly on public land,'' said Roy Brown, a U.S. Fish and Wildlife Service agent based in Wyoming.

On June 3, Fish and Wildlife Service agents confirmed that a male gray wolf found dead last month in the wilderness area was killed by eating meat laced with a gray granular pesticide known as Temik. The pesticide is commonly applied to agricultural crops such as potatoes and sugar beets.

The 2- to 3-year-old wolf wore a radio-tracking collar. On May 14, Idaho Fish and Game officers received a mortality signal from the collar and the animal was found a few yards from a pack trail in the wilderness area.

Last year, Temik poisoning was blamed for sickening several dogs at recreation areas in the Salmon-Challis National Forest in central Idaho and for killing eight dogs and sickening 15 others in Wyoming.