RIVERTON, Wyo. (AP) - Pneumonia has been killing bighorn sheep in Fremont County, and scientists don’t know why.
So they went to the mountains to try to find out.
The illness seems to impact different herds differently.
Near Jackson, for example, sheep die off regularly but rebound like clockwork. Pneumonia hit a herd near Cody, but fewer animals died than in the Whiskey Mountain herd south of Dubois.
The Whiskey Mountain group has been struggling since a pneumonia outbreak in 1991, when herd numbers decreased by 40-50 percent, regardless of animal age.
The population has not recovered to pre-outbreak levels according to Wyoming Game and Fish Department officials.
Kevin Monteith, an assistant research professor at the University of Wyoming, said there is no obvious reason for the variety of impacts pneumonia on bighorns.
He suspects differences in nutrition might be a factor, however.
“If … the nutritional status of animals declines, maybe there’s a threshold at some point in time where they become more susceptible to disease,” he said.
That hypothesis led Monteith and a diverse group of researchers, wildlife managers and volunteers to the top of Torrey Rim on March 19, where he knelt in the brush and ran a sonograph sensor over a bighorn ewe’s rump. Monteith used the machine on the sheep’s abdomen to determine whether the sheep was pregnant, but he also says the sonograph can measure the animal’s fat levels.
“By measuring depth of rump fat and coupling that with palpations we can estimate body fat of an animal - the nutritional status of an animal,” he said.
Other researchers measured and weighed each sheep, estimated its age based on the size of its horns, took nasal and tonsil swabs, drew blood, and collected a fecal sample. The biological samples collected will indicate what types of bacteria the sheep are carrying.
Finally, the scientists attached a collar with a global positioning system beacon to each sheep. Then, they untied the animal’s hobbles, took off its blindfold, and let it go.
The sheep bounded away and ran several hundred feet before stopping and looking the landscape over. Seeming to realizing where it was, it turned in the direction it came from, glanced back at the researchers, and sauntered away.
The sheep had to orient itself because it had been flown through the air blindfolded just before meeting the researchers.
The same was true for every animal Monteith tested that week. He and his crew collared and tested 19 ewes in Fremont County, then traveled to the Jackson area the next day, where they handled 12 more sheep. Ten sheep were collared the day after that near Cody.
A helicopter crew locates each sheep and launches a net on top of it, trapping the animal in place. Next, a crew member drops to the ground to hobble and blindfold the sheep before putting it in a sling hanging below the helicopter for transportation.
The scientists will track the sheep via the GPS collars and catch them twice a year for the next three to five years.
They will track the sheep’s body fat and determine how fat levels relate to survival - both of the adult animals and their lambs.
“Things become revealing with time,” Monteith said. “The questions we’re pursuing are fairly complex.”
Results from Monteith’s research, which was made possible by the University of Wyoming, the Wyoming Game and Fish Department the U.S. Fish and Wildlife Service, and Wind River Indian Reservation Fish and Game, could impact the sheep’s management nationwide.
In the past, similar investigations in mule deer populations showed fat stores were crucial to doe and fawn survival through the winter. As a result, wildlife officials worked to improve forage in the animals’ late summer and fall ranges.
Wyoming G&F wildlife management coordinator Daryl Lutz speculated that his agency might look to improve the sheep’s winter range if the bighorn research draws similar conclusions.
“And I stress, ’if,’” Lutz said, emphasizing that comprehensive results won’t be available for three to five years.
He agreed that experts know very little about the relationship between disease and nutrition in bighorn sheep.
Monteith grew up in eastern South Dakota, hunting and fishing with his family for subsistence, and dreaming of being a game warden. Instead, he decided to study ecology at South Dakota State University, where he became interested in the larger questions behind wildlife management.
“One thing led to another,” he said. “(Now) I’m here today as a scientist trying to understand these animals, and how to conserve them.”
His studies led him to work with Tom Stephenson, a scientist with the California Department of Fish and Game. Stephenson developed the process of using sonography to evaluate body fat in ungulates, and he taught Monteith the same technique.
Monteith brought the method to Wyoming - along with his passion for wildlife, unchanged after years of research - and initiated the bighorn sheep study.
“I still get excited when I see animals, wherever I might be,” he said.
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Ranger staff photographer Tibby McDowell contributed to this story
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Information from: The (Riverton, Wyo.) Ranger, https://www.dailyranger.com
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