Pneumonia found in bighorn sheep in Little Belt Mountains

GREAT FALLS – Nine bighorn sheep from a group that were recently reintroduced into the Little Belt Mountains have died from pneumonia this spring. Several other live bighorn sheep in the same herd have also exhibited symptoms of respiratory disease.

Bighorn sheep were historically common in the Little Belts before they were largely extirpated from the mountain range by the early 20th Century. FWP and several partner organizations worked to restore wild sheep there in 2020 and 2021 by capturing 83 bighorns in the upper Missouri River Breaks and releasing them into the eastern Little Belts. All translocated sheep were fitted with GPS collars.

Pneumonia in bighorn sheep is often fatal and can reduce lamb survival in an affected population. Mycoplasma ovipneumoniae (M. ovi), which is a bacteria that can be carried by wild and domestic sheep, is believed to be the primary agent associated with outbreaks of pneumonia in bighorn sheep.

FWP biologists closely tracked the movements of the bighorn sheep released into the Little Belts and found no evidence of wild sheep coming into contact with domestic flocks. However, tests of at least two bighorn ewes captured from the Missouri Breaks and moved to the Little Belts in December 2021 later came back positive for the M. ovi bacteria. All sheep relocated to the Little Belts were tested for disease, but results weren’t available in time for the relocation.

In recent decades, FWP has not documented pneumonia in the upper Missouri River Breaks population and will continue to closely monitor sheep both there and in the Little Belts.