Mule deer carcasses dotted western Wyoming more than a year ago, the result of one of the toughest winters in decades.
Wildlife managers held statewide meetings to address the carnage with the public. People called regional offices and fretted about the long-term impacts of thousands of dead deer – what would amount to a loss of about 40 percent of the Wyoming Range herd’s population.
More than a year after the 2016-2017 winter that dumped record snow on mountains and lowlands from Jackson to Green River, those long-term results are starting to appear: In at least one deer herd, animals are in better condition than ever.
For wildlife managers, the information is both concise and nuanced.
It shows that smaller herd numbers can lead to healthier animals. It also suggests that bigger herds are not always better. Ultimately, the data leads to the question that if bigger herds aren’t always best, should humans be responsible for keeping numbers down through hunting, or should we let nature make a correction through bad winters, drought or disease?
“It’s part of the discussion of what do we want and what is best for the population?” said Kevin Monteith, assistant professor at the Haub School of Environment and Natural Resources at the University of Wyoming. “Do we want to pack as many animals in there as we can or do we want a robust population that is also providing opportunity for harvest and outdoor recreation and those sorts of things, too?”
Monteith has spent years studying Wyoming’s mule deer, particularly in the Wyoming Range. In a state full of iconic mule deer herds, the Wyoming Range deer are possibly the most well-known. The bucks are impressive, and hunters flock from around the country for a chance to pursue them.
In the late 1980s and early 1990s, mule deer in the herd numbered around 50,000. But a series of bad winters and increased hunting pressure cut the herd down to about 30,000. Wildlife managers tried for years to reach that 50,000 goal again, but realized the deer were not just limited by a bad winter or hunting, but by available food.
In 2015, Monteith and a host of partners from the Wyoming Cooperative Fish and Wildlife Unit, Wyoming Game and Fish Department, the Bureau of Land Management and others started a project studying fawn survival in the Wyoming Range. They collared females who were pregnant in the spring, measured their fetuses with an ultrasound and then tracked births using vaginal implant transmitters — electronic devices that alert biologists to a birth. They then found the fawns and placed collars on them to track their first year of life.
The first two years — 2015 and 2016 — provided what would unknowingly become a kind of baseline data for the group. Then the winter of 2016-2017 hit, and researchers realized they had the opportunity to accurately measure the exact impact of a harsh winter on a population.
“For me as a researcher, this was a phenomenal opportunity to show what this population would look like at a reduced abundance,” Monteith said.
Now not only would the group be able to study the impact of disease and predation on a herd, but also the effects of a harsh winter on deer, and by extension, habitat.
It didn’t necessarily surprise Monteith or his graduate student, Tayler LaSharr, that the condition of deer in the Wyoming Range herd improved this year, but they were impressed by the degree to which they improved.
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Thousands fewer deer competing for food meant the animals that remained could take advantage of an increase in moisture and an all-you-can-eat buffet of shrubs and plants like geraniums and sage brush.
“The does in the fall, when they came off of summer range in 2017, they were the fattest we had ever seen in the Wyoming Range to the point where some of them were classified as obese they had so much fat on them,” LaSharr said.
When they came out of winter and into their spring and summer range, the does that were pregnant had fetuses measuring significantly larger than the previous year.
And then there were the average birth size and condition.
Fawns born in 2017 after the harsh winter measured on average 6.8 pounds. Fawns born this summer weighed on average almost a pound more.
And of 67 fawns born in their group in 2017, nine were stillborn. Only one of 83 were stillborn this year.
“Sometimes you will collar them and they’re little and you can tell they’re not in good shape and even the little ones we collared this year looked hearty,” LaSharr said. “Last year you could tell they were smaller and malnourished and undeveloped because the does we not able to support them in utero.”
While the information might seem intuitive — fewer animals on a landscape means more food, better body condition and fatter fawns — what to do with the information is a little less clear.
“Bottom line is that more is not always better,” said Doug McWhirter, Jackson wildlife coordinator for the Wyoming Game and Fish Department. “Even when you’re talking hunting opportunities, because if the population is at an appropriate size it can be more productive and produce more animals per hunter than if the population were larger and less productive.”
Not only are the fawns bigger and more likely to survive, data from studies on whitetail deer suggest that the males will grow into bigger bucks, Monteith said.
The results from the destructive winter may mean that instead of allowing a herd to grow to its capacity, thinning vegetation on the landscape and creating a herd of undernourished deer, perhaps it is better to keep numbers a bit below capacity.
But that is often an unpopular argument when conventional wisdom says fewer deer means fewer licenses, which means fewer hunting opportunities. New research, however, says that’s often not the case.
If the population isn’t kept down by hunting, it will eventually be hit by some force of nature, Monteith said. It was a bad winter this time. Another time it might be a disease outbreak or a drought.
“The animals that can live through winters like 2016-2017 are the kind of deer we want in this herd unit,” McWhirter said. “They are big, robust, tough deer that will ensure the perpetuation of that population.”