Disease has plagued western bighorn sheep herds for decades. Healthy herds continually succumb to pneumonia bacteria, leaving the future of bighorn sheep, particularly the Whiskey Mountain herd, hinging on some sort of solution. Researchers behind a new paper, published last week in the journal Proceedings of the Royal Society B, may have an answer as they found a direct link between the amount of fat on an animal and the level of infection, according to WyoFile.

In layman’s terms? Basically, the fatter the animal, the less likely the bacteria will cause infection.

As GOHUNT has previously reported, pneumonia has caused massive die-offs among iconic bighorn sheep herds across the West. The deadly pathogens come from domestic sheep, which often mingle with wild sheep on grazing allotments. While the Whiskey Mountain herd once numbered 2,500 animals, since the early 1990s, disease has cut the herd to about 500 members, according to WyoFile.

The new findings mean that there could be a chance to bolster the herd; however, how is still to be determined.

“The Whiskey Mountain herd is so important to wild sheep West-wide, and in Wyoming specifically,” said Katie Cheesbrough, executive director of the Wyoming Wild Sheep Foundation. We aren’t going to give up on it.”

The study began back in 2015 with a helicopter capture of about 24 ewes. Biologists from the University of Wyoming (UW) and the Wyoming Game and Fish Department (WGFD) measured body fat, checked for pregnancies and swabbed noses for pneumonia. Several years later, they repeated the process, adding transmitters to pregnant ewes so that researchers could monitor lamb survival rates. The process was repeated again later that fall as well as in herds near Jackson and Cody, with more than 200 bighorn sheep monitored and tracked for nearly a decade before researchers stumbled upon a pattern.

“Sheep who carry the pneumonia pathogens gain less fat over summer and lose more over winter,” said Rachel Smiley, a University of Wyoming Ph.D. student and lead author of the paper.

However, because the bighorn sheep weren’t making extreme changes in their summer and winter ranges, it took some more time to realize that those infected with pneumonia pathogens had a harder time sustaining healthy fat levels. 

“Before the pathogens were present, those animals could make it and maintain a higher abundance given the nutritional resources that were there,” said UW professor Kevin Monteith. “But when you add a new cost, a new energetic burden the animals are contending with, the range isn’t adequate.”