Stoneberg: Stress Counts with Bighorn Pneumonia

Note about the following column: Bighorn pneumonia is a very popular disease with anyone that wants to eliminate domestic sheep from the western United States.  Any time there is a bighorn pneumonia die off, the finger points at domestic sheep as the cause, usually with no corroborating evidence needed.  An outcry to eliminate the offending sheep follows.  But there is more to the story…

-Sierra Stoneberg Holt

Stress Counts with Bighorn Pneumonia

The Mycoplasma pneumonia organism is found in healthy populations of bighorn sheep. This is true for other species, also. A bison ranch suffered pneumonia losses from Mycoplasma pneumonia when a pack of wolves moved into the area. The ranch had a full-time veterinarian and documented that the cause of death was a Mycoplasma pneumonia organism that had previously existed in the herd without a problem. The veterinarian also documented the increased levels of stress hormones present after the wolves arrived.  M. pneumonia plus stress led to deaths. The ranch euthanized and buried any bison that became ill to stop the spread of pneumonia until the wolves moved on.

Bighorn sheep on the CMR and nearby areas have to contend with a large cougar population. A hunter took a picture of a cougar packing a bighorn lamb. A rancher friend has trail cameras showing cougars.  A hopeful cougar hunter stopped at the ranch after a scouting trip. He had not seen any bighorns but reported cougar tracks and deer remains everywhere. The deer on our ranch went south to the CMR for water in 2021. They did not return as research says they should for the next fawning season. Our hundreds of deer became (and remain) very few. At least the spread of chronic wasting disease is slowed down. I miss our deer. The remnants of the herd now face excess fawn loss because the low fur prices have increased our coyote population.

Domestic animals also suffer from pneumonia (including from Mycoplasma sp.) during stress. Bighorn sheep seem very susceptible to stress and being on the lunch menu is very stressful. Once the cougars exhaust their food sources, perhaps bighorn sheep will need to be reintroduced if no survivors remain in Hunting District 622.

-Rose Stoneberg, DVM, Box 37, Hinsdale MT  59241, (406) 367-9314