Setting Our Sights on Yellowstone, Part 3, Where are the Pronghorn and Elk

 One thing that we noticed in both Grand Teton and Yellowstone was the low numbers of elk and pronghorn, especially in areas where they had always been plentiful in the past. I remember reading an article about elk and deer populations being impacted by Chronic Wasting Disease (CWD) in Wyoming but did not expect the numbers to be so great. I did some internet sleuthing and found the following information in the Mountain Journal, a well-respected digital publication from Bozeman, Montana…

First the pronghorn. Heavy winter snow, coupled with a lethal bacteria hit the Sublette pronghorn herd hard last winter. In 2022, population estimates placed the herd at 43,000 animals; in the summer of 2023, there were about 24,000 left. Of the animals with radio collars for research purposes, 75 percent perished. 

Outbreaks of Mycoplasma bovis, shortened to M.bovis, are rare among Wyoming wildlife. The respiratory infection can be spread from cattle to pronghorns. Although the bacteria isn’t a reportable disease for livestock, assistant state veterinarian Dr. Rose Digianantonio said she’s seen a number of cases.  There’s no vaccine for the infection, which does massive damage to the lungs.

Some sections of the famed migration route, dubbed the “Path of the Pronghorn,” plummeted more than others: roughly 90 percent of the pronghorn that migrate to the northernmost segments in and near Grand Teton National Park died. 

Only 79 pronghorn, compared to the usual 700 or so, made it to the outskirts of Jackson Hole, into Grand Teton National Park and the Gros Ventre Mountain range.

Now for the elk. While Chronic Wasting Disease, or CWD, has spread westward across Wyoming for the last several decades and was recently confirmed in a Yellowstone mule deer, there’s no evidence that pronghorns contract the disease. CWD affects cervids, which, as the only species in the Antilocapridae family, pronghorns are not.

There’s also no cure for chronic wasting disease that targets the central nervous systems of deer, elk and moose. The arrival of CWD at feed grounds represents a critical juncture for wildlife management in Wyoming. The concept of artificial feed grounds, created over a century ago to prevent elk starvation as their habitat was developed, now concentrates high elk densities during winter months in the same areas year-after-year, likely accelerating disease transmission.

Unlike brucellosis, which is also present in elk on feed grounds, CWD is always fatal. On average elk live 1.5-2.5 years after infection before succumbing, and infected animals can spread the disease before showing any symptoms.

The disease’s reach is already extensive. Justin Binfet, deputy chief of wildlife for Wyoming Game and Fish, told Mountain Journal CWD has been detected in 22 of 34 defined elk herds statewide, and in 35 of 37 mule deer herds.

“CWD in and of itself remains one of the biggest concerns we have with managing wildlife populations, particularly deer, into the future,” Binfet said. “There are places throughout the state where prevalence in mule deer has gotten to the point where there are population impacts. We consider it to be an added source of mortality.

Elk on feed grounds behave differently than elk in the wild because they’re densely gathering over longer periods of time and over consecutive years. Naturally, elk move around more than they might on feed grounds, and multiple animals testing positive in one area is an indicator that transmission has been taking place for more than a year.

While the disease poses no known risk to livestock or humans, its potential impact on Wyoming’s elk populations could be devastating.

Most of the CWD data was based on elk and deer, but

CWD also affects moose. I have included a few moose photos from past trips to the greater Yellowstone ecosystem.

If you plan to visit the area in the next couple of years don't be surprised if some wildlife sightings are fewer than in the past.

If you read my earlier posts from our 2025 trip you might recall that we had good luck finding moose in Grand Teton National Park but saw none in Yellowstone this year.

Thanks for visiting, be well, and come back soon.