Pneumonia claiming Asotin Creek bighorns
What had been a remarkably healthy herd of bighorn sheep is suffering from a disease that has plagued other herds in the Hells Canyon region since the late 1990s.
Members of the Asotin Creek herd, which numbered more than 100 animals late last year, are now dying of pneumonia.
"We are already down 30 to 40 percent," said Paul Wik, district wildlife biologist for the Washington Department of Fish and Wildlife at Clarkston. "We think the mortality has the possibility of continuing through the fall, and we may see it continue through the next rut when they have so much contact. We are predicting lamb survival will be quite low this summer."
Pneumonia swept through many bighorn herds in the greater Hells Canyon area in 1995 and 1996. Wildlife biologists and researchers believe the outbreak was triggered when domestic sheep or goats carrying the disease came in contact with wild sheep. Since the initial outbreak, and resulting all-age die off, the affected herds have continued to be plagued by lingering illness and poor lamb survival.
Despite its close proximity to sick herds, as well as the outskirts of Asotin and Clarkston where some residents keep domestic sheep and goats, the Asotin herd represented an island of good health. That changed in January when sheep began to die.
Wik said it appears the disease may have been imported from a wandering ram belonging to the Black Butte herd that lives near the mouth of the Grand Ronde River. That herd previously suffered from the disease and the same strain of bacteria was found in dead sheep from the Asotin herd.
"It seems logical that would be the source of the outbreak but we are not able to say that at this time," Wik said.
Researchers at Washington State University are testing dead sheep from the herd. The disease was found in three dead ewes wearing radio collars and in one ewe killed by a cougar. One dead ewe tested negative for the disease.
Wik said the department is intensively monitoring the herd but has no plans at this time to take other actions.
In November, five sheep from the Asotin herd were captured and taken to WSU for research. All of them tested negative for the disease. Because of herd's health, some animals were periodically trapped and used by researchers trying to learn more about the disease. The Asotin herd has been subjected to highly managed hunting. Wik said it is possible a two-tag hunt previously planned for this fall will continue.
"Based on our survey data we still have adequate number for a very limited harvest," he said.
