Auditor (also The Auditor; before 1986 – November 19, 2003) was a feral dog who lived on Montana Resources properties surrounding the Berkeley Pit, an open pit copper mine and Superfund site in Butte, Montana. First seen at the mine in 1986, the shaggy dog typically avoided human contact. He was given the name "Auditor" because he would appear when least expected. Auditor appeared to be a Puli due to his long, corded coat resembling dreadlocks, typical of that breed. Mine employees provided food, water and shelter for Auditor, who would wander the mine, often disappearing for weeks at a time, interacting with people as little as possible. After he began to show signs of arthritis, aspirin was added to his food. Auditor died on November 19, 2003, at least 17 years old.
Holly Peterson, an environmental engineer at Montana Tech, analyzed hair samples taken from Auditor near the end of his life and found elevated levels of "nearly every element imaginable," with a level of arsenic 128 times that normally found in pet dog hair. Peterson's study was published in the Intermountain Journal of Sciences in June 2006. Following publicity about Auditor, Peterson organized the installation of bronze statues of Auditor by Andrea Wilkinson at three locations in Butte, establishing the Auditor Foundation to memorialize the dog.
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- "Legend in his own time, pit dog perishes". Montana Standard. November 20, 2003. Archived from the original on June 11, 2016. Retrieved 28 December 2018.
- Woestendiek, John (November 2, 2010). "Surviving Butte: The story of The Auditor". ohmidog!. Archived from the original on November 11, 2010. Retrieved 28 December 2018.
- Vincent, Matt (January 8, 2002). "BUTTE MEMORY: 'The Auditor,' Berkeley Pit's shaggy denizen, was 'adopted' by miners". Montana Standard. Archived from the original on September 18, 2017. Retrieved 28 December 2018.
- Watts, David L. (March–April 2016). "Hair Trace Elements Environmental and Archeological Studies" (PDF). Trace Elements Newsletter. 27 (1). Retrieved 28 December 2018.
- Hair Trace Elements Environmental and Archeological Studies, summary of forensic work extending from Peterson's studies on Auditor's hair samples