NORTH DAKOTA OUTDOORS MAGAZINE

Death in the Mud Margins

Ron Wilson

There are a number of things that get in the way of big game animals in North Dakota, especially white-tailed deer, in their effort to reach the numbers wildlife managers and hunters would like to see.

First, there’s the weather where drought and tough winters can hit with equal severity in this neck of the Northern Plains. Then there’s the lack of suitable habitat on the landscape to safeguard deer and other animals during the state’s leanest months and provide sanctuaries for adults to birth and raise young in spring and summer.

Then there’s disease. The silent killers that aren’t as in-your-face as a January blizzard, but at times can pack a significant punch.

North Dakota Game and Fish Department officials confirmed the state’s first case of epizootic hemorrhagic disease in 2026 on Aug. 8 from a whitetail doe near Lake Tschida, said Dr. Logan Weyand, Department wildlife veterinarian.

Starting in early August, Weyand said agency staff fielded 184 reports that tallied 425 mortalities of ungulate species including white-tailed deer, mule deer and pronghorn. The bulk of the fallout was to white-tailed deer in southwestern and south-central North Dakota, with some association along the Missouri River. The hunting units hit hardest were 3F2, 3C, 3E1 and 3E2.

In response to the outbreak, state officials announced in October several conservative harvest strategies in southwestern and south-central North Dakota to safeguard an already slow-to-rebound deer population hit hard by weather and disease in the last five years. One of the strategies, for example, was to prohibit harvest of antlerless whitetails in the hardest hit deer gun units.

Mule deer doe and fawn

Mule deer aren’t hit as hard as white-tailed deer during EHD outbreaks and wildlife biologists believe its because mule deer spend much of their time in the drier, more arid areas on the landscape where the midges don’t survive as well.

EHD is a naturally occurring virus spread by biting midges that is often fatal to whitetails, and less commonly to mule deer, pronghorn and elk. EHD is no newcomer to the landscape as Game and Fish Department officials reported the state’s first documented outbreak decades ago.

“North Dakota suffered its first EHD outbreak in 1962 … between the two units of Theodore Roosevelt National Park along the Little Missouri River,” Department wildlife officials reported in 1988 in North Dakota OUTDOORS. They continued, saying that EHD reared its ugly head again in 1970, 1976, 1981 and 1987.

This whitetail buck was photographed in the Missouri River in 2021 during the state’s last, and likely worst, EHD outbreak on record.

Ryan Herigstad, Department wildlife health biologist, said EHD is cyclical in nature. Considering the weather and the fact that it’s been five years since the last outbreak, it wasn’t shocking that the unwelcome midges, and the trouble they bring, were going to hit the fan.

“The writing was on the wall with the warmer, wet spring that we had that transitioned to hot temperatures and drought, making those mud margins (where the midges live) a lot more expansive on the landscape,” Herigstad said. “It’s been a half decade since our last bad outbreak. Why EHD is cyclical could be a combination of herd immunity that’s left on the landscape and weather conditions and environmental factors … it’s likely a variety of those variables that are playing in into it and contributing to an outbreak.”

The last EHD outbreak in North Dakota was 2021 and was said to be on par with the worst that Department officials had experienced in terms of EHD attributed mortality.

This year’s outbreak is considered moderate by comparison, but significant nonetheless given how few deer were on the landscape to start this year compared to 2021.

Like EHD outbreaks in the past, white-tailed deer top the list of dead ungulates. Ben Matykiewicz, Department big game management biologist, said this is likely because whitetails frequent those mud margins considerably more than other big game animals.

“At this point, we think it’s kind of an exposure thing. Whitetails are just more likely to inhabit those environments where the midges are,” he said. “While pronghorn and mule deer will visit those areas to get free-standing water, they’re more likely to be up in the more arid, drier environments where the midges can’t survive as well. Whereas whitetails almost exclusively live in those creek beds, river bottoms, wooded areas where you see higher loads of midges.”

EHD is a well-studied disease phenomenon across the United States. Scientists know that the disease comes and goes and that whitetails can certainly survive in the long term with EHD. Even so, there’s more to learn in an effort to manage the disease.

“North Dakota and a lot of other states deal with EHD and currently there are limited options on ways to manage this disease and reduce the impacts on white-tailed deer in particular,” Weyand said. “Given the continuous impacts it is having in North Dakota, we are taking some new research approaches this year focused on the virus, and then soon to come the vector. The goal starting this year is to dive deeper into some of those different factors that are important from a research standpoint, to see what solutions may eventually be out there.”

When described by scientists, EHD is a nasty disease, and an infected deer can die from the virus as quickly as one to three days.

“When the deer is bitten by a midge and then infected, that virus will enter the lymph system and it starts to replicate in the deer’s body,” Weyand said. “In a lot of these carcasses, what we see is buildup of fluid in the chest cavity and around the heart, sometimes in the abdomen. And that is because EHD results in a systemic issue where fluid leaks out of blood vessels due to inflammation.”

While a killing frost or two will end this year’s EHD outbreak, hurdles remain in the effort to rebuild North Dakota’s whitetail population.

“The two biggest factors in this effort right now are time and habitat. These animals still need time to recover from the tough winter of 2023. We’re still seeing the effects in the eastern end of the state, particularly where we have far less habitat,” Matykiewicz said. “A rebound in the population, the subsequent growth after that disturbance, is just so much slower with there being a lack of resources on the landscape. But even where we have better habitat, better resources, particularly around river valleys, stream beds and riparian areas, it’s still going to take time because we’re going from a fairly low-density deer herd to a lower density deer herd.”

Return to North Dakota Outdoors November 2026 Edition