Game and Fish wraps up three-year mule deer study

BUFFALO — Three years of work came to a ceremonious end the morning of Dec. 16 as Wyoming Game and Fish Department officials and other stakeholders captured and examined a collared mule deer for the final time.

The study, conducted to help manage a declining Upper Powder River mule deer herd near Kaycee, will give biologists like Cheyenne Stewart, Game and Fish Sheridan region wildlife coordinator, an idea of the biggest problems facing the herd.

Game and Fish, along with the University of Wyoming Haub School of Environment and Natural Resources and the Bureau of Land Management, captured, collared and followed 119 adult doe mule deer over a three-year period. In total, 70 deer were collared at a time; 67 died during the study and had their collars re- deployed, Stewart said.

“That is more than we expected and, in general, high rates of adult doe mortality can be a concern for herd productivity and management,” she said. “But it is too early to draw any specific conclusions because our final captures only mark the beginning of our data analysis. We still have a lot to learn about the relative impacts of different causes of mortality observed and how those may impact deer within the herd unit differently.”

The study required cooperation with more than 40 landowners, Stewart said. Each year, crews set up staging areas and completed captures on private land with permission from landowners.

The goal for the final capture was 52 deer. Helicopter crews were able to capture all but four, whose collars will automatically drop off in January, at which point Game and Fish will review their movement data, Stewart said.

The capture process, after three years of practice, runs smoothly. Typically, two deer are captured at once. The animals are blindfolded and given a mild sedative to keep them calm as they are transported, probed and prodded.

Aside from a few attempts to wiggle away from researchers and subsequent bleats in protest, the mule deer largely submitted to the scientists' testing. And it's all done pretty quickly; the team was able to capture and take samples from four deer in 30 minutes.

Researchers removed the collars and piled them in the back of a truck after three years of following the herd's GPS coordinates. After a series of tests researchers turned the deer loose, either by walking them away from the staging area and letting them take their own tentative first steps back into the wild, or by hitching them again to the helicopter to get dropped off where they came from.

Stewart said that use of a helicopter drop-off depends on how far away from the staging area the deer were picked up. If it's more than a 3- to 4-mile radius, the helicopter is used.

The 30 minutes of discomfort for the deer makes available a comprehensive data set that shows the health of the herd through each individual animal's measurements - weight, length and girth - as well as blood samples to analyze genetics, fecal samples to test for parasites and rectal tissue samples to test for chronic wasting disease. Researchers also performed an ultrasound to measure body fat.

The results for individual deer health are instant, though a comprehensive data set that characterizes the entire herd won't be available for several months. Game and Fish, along with University of Wyoming professor Kevin Monteith, will start analyzing the data in the spring, Stewart said.

Studying these same deer each year could help researchers learn about deer movement, habitat selection and how weather influences body condition of deer coming off summer range, Stewart said in a Bulletin interview at the start of the study.

GPS data on the collar is recorded every two hours, tracking their movements. Dan Thiele, former Sheridan region wildlife coordinator who kicked off the study in 2019, said one of the more surprising bits of data so far are deer movements across the Bighorn Mountains.

In the end, researchers learned that some deer are resident deer — occupying the same habitats year-round; some are short-distance migrants — moving up and down the elevational gradient; and some are long-distance migrants — moving up in elevation and north into the Bighorn Mountains.

The collars also notified Game and Fish if the deer wearing a collar died. From there, Game and Fish employees retrieved the carcass, which was then sent to Jennifer Malmberg, pathologist at the Wyoming State Vet Lab and an assistant professor in veterinary sciences at the University of Wyoming, who would determine the cause of mortality.

“Part of this study is to try to get to the bottom of why that is, what is taking these deer out of the population so quickly,” Malmberg said. “So far, we found a lot of chronic wasting disease, some winter kills, some starvation type of issues. And then this year, we also had viral hemorrhagic disease.”

Stewart said that mortality rates were higher than expected, which could be a concern for herd productivity and management.

This kind of research — and the subsequent ability to make science-based management decisions — has only come about in the past 10 to 20 years, Thiele said.

“It was surreal when we finally collared the deer and got going,” he said. “We certainly have had some variation in precipitation over that (three years), and whether that will show in the body condition on some of these deer or not, I don't know. Research tends to answer some questions but always generates more, so there will be questions we don't have answers for." 

Stewart said regional biologists learn a lot about the big-game herds they manage through annual survey work, general field time, habitat projects, population modeling, public contacts, harvest surveys and hunting seasons. Partnering with researchers can fill in the gaps for field managers to make more informed management decisions.

“This type of work can help us with immediate decision-making, such as setting annual hunting seasons, as well as address longer-term resource management questions and concerns,” Stewart said.

Once biologists and researchers analyze the data, the department will host public meetings in Kaycee and Buffalo to share the results and to discuss management options, Stewart said.

“We want the data to help inform us about the most immediate concerns for these deer so our management decisions are effective and rooted in sound science,” Stewart said.