In 2009 a dead, radio collared wolf turned up in Rio Blanco County, Colorado. After a lengthy investigation the U.S. Fish and Wildlife Service believes the wolf was illegally poisoned with "Compound 1080". The Denver Channel has a detailed write up  on the wolf's travels and eventual demise.
The map accompanying the article is impressive and highlights the great distances some predators will travel in the course of their lifetime.
State and federal wildlife officers could not find evidence of traps and poison baits in the area around the wolf's carcass, authorities said. Investigators also were unsuccessfully in searching for poisoning evidence along the radio-tracked path the wolf traveled just before it was killed. Several carcasses were found, including multiple old sheep carcasses and one coyote carcass, but no illegal poisoned bait stations were discovered, authorities said.