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

Black Butte Herd

Population Status and Trend Analysis
The Black Butte herd suffered a major Pasteurella die-off during the winter of 1995-96, reducing the population from nearly 200 to less than 50. The management objective will be to restore this bighorn sheep population to 150-200 animals.

Aerial surveys are conducted in conjunction with post-season elk surveys in March, in order to determine population trend, and herd composition at the low point of the annual population cycle. The Black Butte bighorn sheep population has remained fairly static since the die-off of 1995-96.

Lamb production and survival has been monitored closely since the die-off. Lamb mortality due to pneumonia has taken a high toll of lambs shortly after birth in 1996 and 1997. Lamb mortality is still high but tends to occur later in the fall to early winter.

Habitat and Trend
Yellow-star thistle continues to spread into Black Butte-Grande Ronde drainage. Efforts will continue to control and reverse the spread of this noxious weed. Combinations of herbicide, biological controls, and re-seeding may be tried in the future.

Disease and Parasites
The pneumonia induced die-off appears to be running the usual course over time. Lamb survival is poor. To date, we have not been able to isolate the factor responsible for lamb mortality, whether it is a bacteria (Pasteurella) or a virus.

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

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

Management Conclusions
The Black Butte herd is struggling due to the Pastuerella die-off that occurred in 1995-96. The population will not increase significantly until annual lamb survival reaches 30+ lambs/100 ewes.

Contact with domestic sheep is still considered a major problem for this herd. A sizeable domestic flock is present on private land adjacent to the Joseph Creek Wildlife Management area. This problem will continue until the public understands the threat domestic sheep pose to bighorns.

"Twister", Winter 1998	"Twister", Winter 1998	"Twister", Dec. 2000
"Twister", Dec. 2000	"Twister", Dec. 2000	January 2001
"Twister", Dec. 2000	November 1998	"Casper", Winter 1999