SUBLETTE COUNTY – Wyoming Range mule deer will likely make a poor showing after the past winter’s deep snow.
Wyoming Game and Fish (G&F) biologist Gary Fralick addressed what has been learned – and what is feared – at the Sublette Wyoming Public Lands Initiative meeting on April 5.
Fralick was providing wildlife information and updates to the committee as it reviews local wilderness study areas.
Regarding 63 mule deer fawns that were radio-collared shortly after birth last spring in the Wyoming Range, Fralick said 58 percent died between June and September 2016.
“Twenty-six made it to winter range and those have all died now,” he said.
Some fawns that were not collared might have survived, he added, and upcoming winter mortality surveys should reveal if that’s the case.
Summer mortalities were due to disease, specifically adnovirus, as well as predators, mainly coyotes and black bears.
Winter deaths were likely due to starvation, according to Fralick, who said in general mule deer were already in poor body condition when captured and tested last year.
“Coming into this winter, on Dec. 16, they found the lowest percent of body fat in mule deer does coming into winter range,” he said. “(Researcher Keith) Montieth said it was the poorest body shape of any year he’s ever studied.”
Montieth, the University of Wyoming and other organizations including Muley Fanatics are working on research projects for the Wyoming Mule Deer Initiative (WMDI), which began in 2013.
Seventy does with the Wyoming Range herd are collared and their fawns will be collared this spring shortly after birth. They are captured in March and December to be measured and preg-checked. Their fawns are fitted with expandable collars that stay on for six to eight months.
The WMDI supports studies of the very poor rates of fawn ratios and survival in the Wyoming Range, “an enigma for the last 25 to 30 years,” Fralick said. “With (poor) fawn survival in the Wyoming Range, the population is unable to sustain growth over time.”
The fawn to doe ratio “rarely” hits 60 per 100, with 80 per 100 the long-term goal.
“It’s going to be the highest ever in the Wyoming Range,” he said, adding as much as 75 percent to 90 percent fawn mortality is possible. “It will be very, very substantial this year.”
The “usual” mule deer mortality rate in that herd has been around 20 percent for the past five winters of open range conditions. However, very few or no adult mule deer were found in surveys after the past several winters.
“Winter doesn’t just take fawns,” Fralick added. “It takes all age classes. … There’s still mortality in front of is. It’s going to take a lot of animals.”
The initiative received another two years of funding to study mule deer recovery after the past extreme winter, he said. “This is the winter we were looking for in the Wyoming Range.”
“Habitat” is a key component in how these mule deer will survive and thrive – “how they live in and respond to it,” he said.
One three-year project is looking at the nutritional value “green wave” as springtime rolls north and wildlife graze along the new growth. Weekly, the grad student gathers mule deer scat and clips vegetation; both are analyzed to learn how the plants change and how the animals do over time.
“Linking the individual environment to population growth is essential to fawn survival,” he said.
Better quality forage is also important for livestock grazing on public land and WSAs, he added.
Fralick also addressed a question about mule deer response to “high-quality habitat” located near oil and gas development as the subject of another grad student’s master’s thesis.
“If deer are in poor condition they will respond differently to high-quality forage around human development,” he said. “They view it as potential predation, versus poor-quality habitat where they might decide to expose themselves to the risk.”
For more about the Wyoming Range mule deer herd, go to wgfd.wyo.gov.