Washington Chapter | Foundation for North American Wild Sheep ( FNAWS )

Wenaha Herd

Population Status and Trend Analysis
The Wenaha herd suffered a major Pasteurella die-off during the spring and summer of 1996, reducing the population form approximately 90 bighorn sheep to less than 50. The management objective will be to restore this bighorn population to 90+ animals. This population will not increase significantly until lamb survival reaches 30+ lambs/100 ewes.

The Wenaha bighorn sheep population has remained fairly stable since the die-off but lamb survival has been very poor. Lamb production and survival have been closely monitored since the die-off. Lamb mortality due to pneumonia continues to take a high toll of lambs shortly after birth.

Habitat Condition and Trend
Habitat conditions on ODFW and National Forest lands are good, but private lands have been impacted by overgrazing. Yellow-star thistle could become a major problem if the rate of spread is not controlled on the lower Grande Ronde river.

Augmentation/Habitat Enhancement
The U.S. Forest Service is proposing a series of controlled burns within the boundaries of the Wenaha-Tucannon Wilderness. This will improve habitat conditions for bighorn sheep.

Disease and Parasites
The pneumonia die-off appears to be running the usual course over time. Lamb survival has been very poor since 1996.

Scabies continues to be a problem, but Rocky Mountain bighorns appear to deal with this nuisance fairly well. However, in some years, severe infestations may cause problems for lambs and reduce survival rates.

Lung worm levels appear to be holding at low levels based on analysis of fecal samples from radio-collared ewes and necropsied individuals, and is not a problem at this time.