The bighorn sheep is perhaps the most iconic North American big game animal and many hunters aspire to make a sheep hunt the pinnacle of their hunting careers. Unfortunately bighorn population counts have been in free-fall for some time. Dr. Teresa Zimmerman of Chadron State College documents the fall of the bighorn in this article .
Zimmerman, who studied bighorn sheep at Badlands National Park for her doctoral dissertation, noted that bighorns and humans have coexisted for about 30,000 years, but major declines have occurred in just the past 150 years. During that period, the bighorn population in North America has deteriorated from an estimated high of 4 million to a low of 22,000, she said.
As the article notes, bighorns are particularly susceptible to pneumonia transmitted from domestic sheep populations. Bighorn pneumonia can be rapidly spread once it is contracted within a herd population. Recently Montana wildlife officials announced  that they were not able to stop a pneumonia outbreak in the "Anaconda" herd of bighorns.