JACKSON, Wyo. – As a group of graduate students moved around, probing, pushing and drawing blood from three bighorn sheep, Aly Courtemanch kept his eyes peeled for something in particular.
âThat one looks really good,â the Wyoming Game and Fish biologist said, pointing to one. But, descending the line just below Curtis Canyon in the Bridger-Teton National Forest, she found a better competitor.
“This one looks very, very good,” she said. “Really nice and healthy.”
But as the population of Jackson’s herd, which occupies the Gros Ventre Range east of the valley, grows, not all of its woolly wild members look so good, reports the Jackson Hole News & Guide.
Population fat levels, which biologists consider a measure of an animal’s nutrition, are declining, Courtemnch said.
And that makes her and researchers like Kevin Monteith, a professor at the University of Wyoming, fear that sheep populations are approaching another death from pneumonia, like the one that killed 40% of the herd in 2012. The researchers are therefore studying whether limiting the number of sheep – and, therefore, limiting the amount that herd members can compete for food would prevent another death from pneumonia.
To do this, they plan to ask if the public would support a sheep hunt.
âThe assumption is that if we can reduce the numbers through hunting, we should see these sheep react with better body conditions,â Courtemanch said. “This will be one of the first times, if not the first time, that this has been done.”
But we don’t know what such a hunt would look like.
While the elk are hunted each fall to manage herd numbers, the management of the bighorn sheep is different.
Sheep are much less numerous than elk in the western mountain, and hunting tags are generally limited to rams – and generally rare.
There were only 12 tags issued in 2021 for male bighorn sheep in the Jackson de Gros Ventre herd. And Courtemanch said a sheep hunt had only been permitted once before in Wyoming and rarely in other parts of the West. It is therefore a relatively new tool.
Game and Fish plans to make a more detailed proposal, including the number of beacons that could be offered, in March. An open house and an opportunity for public comment would precede a proposal to be sent to the Wyoming Game and Fish Commission for approval in April.
This proposal would likely include plans to study the impact of hunting on fat levels and body condition in Jackson’s herd, building on research that Courtemnch and Professor Kevin Monteith of the University of Wyoming conducted last Thursday.
Pneumonia, introduced to Rocky Mountain bighorn sheep primarily through their interactions with domestic sheep, is often the cause of massive population collapses in wild herds. But different herds respond to pneumonia pathogens differently.
Monteith said the Whiskey Mountain herd, which lives around Dubois, has âstruggled mightilyâ for years. It experienced a major demise in the 1990s and continued to decline.
Jackson’s herd, on the other hand, went through cycles of decline and rejuvenation.
This has led scientists like Monteith and Courtemanche to wonder why two populations of sheep with the same diseases behave differently. They are looking to see what factors other than disease might play a role in the trajectory of the two populations.
âBefore we started, we focused a lot on bug hunting,â Monteith said, pointing to Mycoplasma ovipneumoniae, a bacteria that can cause pneumonia in bighorn sheep.
But he said just looking at pathogens is only part of the picture.
âAll of these sheep have M. ovi,â Monteith said, using an abbreviated name for the bacteria. “But their performance is so different.”
Recognizing this, he began to wonder what scientists lacked to explain the plight of different populations of bighorn sheep.
As a nutrition environmentalist, the Wyoming professor began to focus on what an animal eats and its fat stores.
As a helicopter crew circled back and forth between the foothills of Curtis Canyon, finding and capturing radio collared sheep, then sending them back to a staging area, Courtemanch and Monteith thought about the grease and its link to sheep health.
Generally, a large sheep is a healthy sheep. Measuring the size of bighorn sheep can indicate the health status of the population. Monteith – who has been called the “fat man” for his interest in fat – said fat is not an indicator of an animal’s nutrition. It is an aggregate measure of what animals go through, such as giving birth to a lamb and finding quality food, or not.
“It’s a currency that tells us how good things were, how difficult things were,” he said.
As Jackson’s herd population grows, Courtemanch and Monteith both reflect on body condition and its connection to the bighorn sheep’s ability to resist diseases like pneumonia. This is because, in the past, as the herd reached a population of around 500 sheep, its members died in large numbers from pneumonia.
For example, the number of herds fell 40%, from 417 in 2011 to 243 in 2012. About 10 years earlier, the number of the same herd fell from 503 to 132: a decrease of 73% in just a few years.
As the population rebounds again – the most recent count, in February, was 491 bighorn sheep – Courtemanch said fat levels were dropping.
This leads her and Monteith to wonder if the cycle of death has something to do with body condition: if sheep populations get to a level where they fight too hard for food, end up poorer. health and more susceptible to pneumonia, then catch the disease and die.
âMaybe we’re getting too many sheep,â Courtemanch said. “They have to fight for food, they don’t get enough of it, and therefore their fat goes down.”
Thus, wildlife managers envision a sheep hunt as a possible tool to prevent sheep from competing with each other, depleting fat stores and body condition, and possibly setting the stage for death from the disease. sickness.
âAs you have more and more animals in the landscape, there is less food per animal,â Monteith said. âThen we see these crashes. So the idea is, well, what if we could moderate the density in part of this herd through a harvest of females? “
They hypothesize that round sheep may be more successful in surviving life-threatening pathogens.
Last Thursday, as Courtemnch focused on collecting data on captured bighorn sheep, student researchers deployed a test that humans have become too familiar with amid a global pandemic.
A student stuck a long cotton swab into the nostril of a captured sheep. The student spun it a few times, then pulled out the white cotton swab, now looking black and a little muddy.
âOh, it’s a little dirty,â Courtemanch said with a laugh. âThis is how we test for pneumonia bacteria. Identical to a COVID test. “