WDFW to conduct helicopter survey of bighorn sheep in southeast Washington

SPOKANE- Washington Department of Fish and Wildlife (WDFW) biologists will survey bighorn sheep via helicopter Dec. 12 and13, conditions permitting. This work will take place on Joseph Creek and the Grande Ronde River from the mouth of the river near Heller Bar to close to Troy, Oregon. This work involves a helicopter flying low, which may catch the attention of area residents. 

These routine surveys help WDFW determine the health of the bighorn sheep population in the Black Butte and Mountain View sub herds. Bighorn sheep are highly susceptible to a respiratory disease caused by the bacteria, Mycoplasma ovipneumoniae, or Movi for short. Movi causes pneumonia, which can affect bighorns of all ages and impact bighorn populations - there is no treatment or vaccine for Movi. 

“Bighorn herds in southeast Washington were impacted by a pneumonia outbreak in late 2023, which has spread among the herds along the Snake and Grande Ronde rivers, and more recently Movi was detected in Asotin Creek,” said WDFW Acting District Wildlife Biologist Mark Vekasy. “These surveys provide an opportunity to get a look at the bighorns in this area and determine the magnitude of the die-off compared to population estimates from last year.”  

In the case of the Black Butte herd, staff cannot adequately estimate the number of bighorns from ground surveys due to the roadless area the sheep inhabit along the Grande Ronde River corridor.  

Bighorns will not be captured during these surveys, and biologists will classify sheep by age and sex as quickly as possible to avoid undue stress. Data gathered from the survey will be used to obtain a baseline estimate of herd composition and number, and to confirm the mortality estimates derived from the mortality of radio-collared sheep, which currently stands at over 60%. 

Washington is home to an estimated 1,690 wild bighorn sheep that range in 17 herds in eastern and central Washington.  
 
WDFW works to preserve, protect and perpetuate fish, wildlife and ecosystems while providing sustainable fish and wildlife recreational and commercial opportunities.