You may have heard about the microorganisms that have adapted to the toxic water of the Berkeley Pit, but there’s another, larger creature that has become something of a local legend. 

During his life from around 1986 to 2003, the ghostly dog-bigfoot hybrid (or Puli if you want to get technical about the breed) lived alone in the Berkeley Pit. Miners called him “the Auditor” because he had a habit of showing up when he was least expected. The Auditor was not friendly to people, so mine workers built him a doghouse and would leave food. As he started to show his old age, workers began putting baby aspirin in the food. Photos of the Auditor were displayed alongside ore samples and awards in a case in the mine’s office.

While the Auditor was still alive, Holly Peterson, an environmental engineer from Montana Tech, clipped a sample of his fur and found elevated levels of arsenic and other toxic elements, lending to the mythology of Butte Tough: an old mining town that survives among its ghosts.

Today, several monuments have been erected around Butte to honor the memory of the tough old dog. They can be found outside the Butte-Silver Bow Public Archives and the Chamber of Commerce