Deer dynamics: Student helps unlock mysteries of chronic wasting disease

Hundreds of GPS collars. Thousands of movements tracked across the mountains. Millions of photographs.

These are the elements now being assembled to give researchers a clearer picture of chronic wasting disease, a highly contagious, deadly disease affecting a large number of deer and elk in Arkansas.

Just how many animals are affected is still unknown, but that’s one of many questions students and faculty at the University of Georgia Warnell School of Forestry and Natural Resources are tackling with the study. It’s been two years since it launched, said Warnell doctoral student Marcelo Jorge, and he and his team will continue to collect information for another two years—plus time spent after field work to analyze the data.

But what they are gathering, he said, is promising and offers a lot of options for the future.

“It’s a massive study that will eventually take five to six years to complete. But the data from this study can be written on other subjects for decades—I can re-create my master’s thesis with the data we’re collecting here,” said Jorge, who has extensive experience studying wildlife populations. The opportunity to examine disease across the landscape was an element that attracted him to the project, though.

“I am, at heart, a deer guy. … for me, (chronic wasting disease) is a huge issue and as a hunter myself, I can see how this can affect hunting,” added Jorge. “With the decreasing hunting population we already have, this can only exacerbate those issues. So, this is near and dear to my heart, but the project also gave me the opportunity to learn new things from new people.”

The project, funded by a large group of organizations and spearheaded by the Arkansas Game and Fish Commission, has several goals centered around the spread of chronic wasting disease, or CWD, in the northern part of the state. This fatal neurological disease was first detected in Arkansas in 2015 among elk populations, but soon was detected in deer—although later testing suggests the disease had been in the state for much earlier.

Chronic wasting disease is a growing problem across the country and abroad. It affects members of the cervid family, which includes deer, elk and moose, and is transmitted through body fluids. But it’s also persistent in the environment and can live for years in soil. There’s even evidence it can be absorbed by certain types of grass; when it’s then eaten by deer, it can potentially perpetuate the cycle.

Alarmed by the high rate of disease reported by hunters, Arkansas officials decided to pursue the study. To date, it’s the largest study of CWD in the Southeast and the first of its kind. Researchers are incorporating multiple capture techniques, tracking deer across a wide swath of the Ozark Mountains, collecting a variety of samples and vital statistics from each deer and incorporating hundreds of cameras to capture movements of deer and other animals on the landscape. 

The cameras are particularly useful, added Jorge, because of the potential for use in other studies and projects. They even proved useful with wild hogs—the research team was able to identify previously unknown sounders (two or more adult sows and their young) and assisted state wildlife officials in removing them.

“Because this is a disease that works on a whole different set of dynamics, like landscape and predator communities, all these things come together to impact the disease,” said Jorge. “This study definitely benefits Arkansas, but within the larger body of literature on CWD, it’s beneficial. Because a lot of other southeastern states are finding CWD, those states will also benefit from this research to get a leg up on how to manage it.”

Although the team is only halfway into the field work, its members are starting to sort through data to identify preliminary trends. For example, they are looking at survival trends, and what factors affect deer survival if they don’t have CWD. During the study, Arkansas experienced some polar vortex weather events and the team discovered that low temperatures disproportionately affected CWD-positive deer.

The unique terrain of the Ozarks also plays a role in survival. Jorge noted that deer have slightly lower survival rates in flatter, open areas compared with the rugged mountainous terrain, but overall survival rates are relatively similar. This is where state wildlife officials can step in and work in concert with deer hunters to help control the population.

“That might be an opportunity for agencies to target these rougher areas, to bring down the positive deer survival probabilities in areas where their survival is similar to healthy deer,” he said. “By focusing on areas where survival rates are similar, it means you don’t have to target the fields. That’s where there are more natural predators and hunters.”

In the first two years of the study, Jorge’s team found 17% of the CWD-positive deer they were tracking died solely from the disease. It’s a large percentage, and that number points to a large number of deer that are dying of the disease across the landscape—more than would have died by natural causes alone. 

Still, it will take time to process the data to get a larger picture. And then there’s the genetic information they’re collecting, tissue samples taken from the field and camera images—all of which must be documented, cataloged and entered into computers for the team to analyze. Jorge is also interested in the role predators play in controlling the CWD-positive population—and also potentially spreading the disease through scat and other methods.

His team is now looking forward to cooler fall temperatures, as well as the opportunity to implement artificial intelligence into the data processing. Eventually, Jorge will have enough information for five chapters of a doctoral thesis. “And then there’s a bunch of side projects,” he added. “Potentially, in the future, other graduate students could work on this data to look at, for example, how prescribed fire comes into play.”

That’s the beauty of the study, he said. “There’s all these other benefits that we didn’t think of prior to this study, that this study is adding to as well.”