Biologists look for clues to bighorn sheep die-off

Bighorn sheep continue to die from complications brought on by pneumonia in the East Humboldt Range and the Ruby Mountains, according to biologists with the Nevada Department of Wildlife.

"We have found 61 dead bighorn sheep in the East Humboldts and 18 in the Ruby Mountains for a total of 79 sheep over the last three months," said Caleb McAdoo, NDOW big game biologist. "In other words, we have observed mortalities of 31 percent of the herd in the East Humboldts and 11 percent of the herd in the Ruby Mountains."

McAdoo cautions the public that the extent of the effects of the disease won't be known until later in the spring when aerial surveys of sheep populations are performed. Biologists anticipate that the magnitude of the die-off may be much greater than presently known.

According to McAdoo, this isn't uncommon. Other states around the West, including Washington, Montana and Utah, have also experienced die-offs in their wild sheep populations due to pneumonia. During the winter of 1995-1996, the Ruby Moun-tain sheep herd lost approximately 80 percent of its population to pneumonia, though this is the first major disease event in the East Humboldts since bighorns were reintroduced there 18 years ago. Recently, 95 percent of the Hays Canyon herd in northwestern Nevada was likely lost to a pneumonia outbreak.

"Unfortunately, there is no known cure, treatment or protocol for pneumonia in bighorn sheep," said McAdoo, "but we are going to use the data collected from this disease event which may help in future outbreaks."

NDOW biologists and veterinarians have been performing a number of tasks, setting the stage for future study. This includes tagging and putting radio telemetry collars on sheep in both herds, taking biological samples from both live and dead sheep, and administering antibiotics to more than 60 sheep.

To avoid putting more stress on the animals than necessary, work is being done from the ground as much as possible, as helicopters cause the animals to try to evade and escape, using energy and making them more susceptible to pneumonia.