Photo credit: AJ Pagano

Wyoming researchers are embarking on a new multi-year study aimed at understanding why bighorn sheep are susceptible to pneumonia. The study will look at overall herd nutrition to determine if well-fed, healthy bighorn sheep are less prone to contracting pneumonia. A crew comprised of biologists from Wyoming Game and Fish (WGF) and Wyoming Cooperative Fish and Wildlife Research Unit (WCFSRC) will also look at herd size which could be another factor in disease resistance.

“It’s hard to say whether there’s truly a pattern yet, but we have two instances where the population grew to about 500 animals and then went through a pneumonia outbreak,” says WGF biologist Aly Courtemanch. Pneumonia is linked back to contact with domestic sheep.

Along with gathering basic research from the bighorns (girth and length; fecal, saliva and blood samples; ultrasounds to measure body fat and check for lambs), biologists are also tracking herd size as a potential pattern that may predict when another pneumonia outbreak could occur. The first one happened in 2001 with another following in 2011. The herd recovered, but it appears that once herd size grows beyond a certain number, bighorn sheep may be more susceptible to the deadly virus.

Coupled with disease monitoring in the Jackson sheep herd over the past few years, biologists also plan to study herds near Dubois and Cody. By studying multiple herds, they may be able to conclude why some herds seem to avoid the disease and others do not. 

WGF disease specialist Hank Edwards hopes to combine their study with similar research taking place in Montana and Colorado so that researchers can analyze the link between pneumonia and bighorn sheep die-offs on a broader scale. Edwards says, “There’s lots of factors that lead to die-offs — more than just bugs. We need to figure that out. What are those factors, and can we manage to prevent some of those?”

“We’re trying to figure out that piece to the puzzle,” adds Courtemanch. “No one’s ever looked at that before — how body condition really plays into these pneumonia outbreaks.”