Statewide disease outbreak causes localized deer deaths

Last week, Montana Fish, Wildlife & Parks big game chief Brian Wakeling told the FWP commission that biologists have been seeing outbreaks of hemorrhagic disease among deer, mainly white-tailed deer, and antelope in spots across the state.

Hemorrhagic disease is an overall term for two specific viruses that kill deer and antelope: epizootic hemorrhagic disease or EHD and blue-tongue disease. Both are carried by midges that hang out in damp areas and transfer the disease when they bite animals coming to the water to drink. The disease causes internal bleeding and has a rapid onset of a couple weeks so biologists don’t see the symptoms until it’s too late.

This fall has seen clusters of white-tailed deer dying along the Clark Fork River west of Missoula and around Frenchtown. FWP Region 2 biologists in Missoula have also received reports of possible incidents near Potomac and Lincoln in the Blackfoot River Valley. Tissue samples are being sent to the FWP laboratory for testing to confirm the cause. The Confederated Salish and Kootenai Tribes Wildlife Program reported Sunday that dead deer and possibly a few elk have been reported near Hot Springs and in the Mission Valley.

The disease is also affecting white-tailed deer in numerous sites in eastern Montana, especially along the Milk River along the Hi-Line and the Yellowstone River downstream of Billings. Wakeling said one landowner had described 60 dead animals.

This isn’t the first time that outbreaks have occurred in western Montana. But they didn't start happening until fall 2013, the first year that outbreaks were reported west of the Continental Divide, when nearly 400 deer were reported dead with most deaths occurring in the same areas as this year: along the Clark Fork River from Harpers’ Bridge to 10 miles downstream and in the Mill Creek area northeast of Frenchtown.

FWP Region 1 in northwest Montana didn’t record any outbreaks until around 2016. That first outbreak wasn’t as severe as what’s happening this year, said former FWP biologist Tim Thier. This yeary, one outbreak is occurring near the lakes between Eureka and Trego and another is along the Pleasant Valley Fisher River west of Marion.

“The frost kills the midges, and we still haven’t had any serious frost yet. Here it is, darn near the middle of October,” Thier said.

Climate change is probably contributing to the likelihood of an outbreak by causing temperatures to stay warmer into the autumn months. Outbreaks occur in late summer and early fall when biting midges are active, especially when daily temperatures are above average for an extended period of time, Wakeling said. That was the case for this September, which was the second warmest on record for western Montana, with average temperatures hitting almost 7 degrees Fahrenheit above normal for both Missoula and Kalispell, according to the National Weather Service Missoula Office.

The onset of cold, fall weather usually kills the biting flies that spread disease so Monday’s light snow and cooler temperatures may signal an end to the outbreak. In the past, the shift to cooler fall weather has meant that outbreaks are short-lived.

While the disease can affect other species, white-tailed deer tend to be more affected because of where they live and the fact that they are more abundant so the disease appears more devastating, Wakeling said. Fortunately, affected populations tend to be localized. However, in 2008 and 2009, Montana's antelope herds declined significantly due to a blue-tongue outbreak and the populations are still struggling to recover.

During Thursday’s meeting, the FWP commissioners voted to put limits on the number of over-the-counter white-tailed deer tags that can be sold for the upcoming general season in northeastern Montana’s Region 6. Since disease has already affected the white-tailed deer population - although Wakeling said it’s not to a level that’s biologically concerning - the idea is to limit additional effects from hunting.

The commissioners discussed other solutions such as temporarily banning hunting in locations where outbreaks occur. Biologists said it might be difficult to define and enforce the areas where the bans should be. And they didn’t want to expand the ban to cover an entire hunting district because districts in eastern Montana are huge so it would leave more deer that could damage private lands or spread chronic wasting disease.

Commission chair Leslie Robinson charged the department with coming up with possible methods to create smaller areas for bans since outbreaks tend to occur each time in the same areas such as along the Milk River.

Region 2 commissioner Jeff Burrows said hunters in his district would likely support a district-wide ban if it was only for a year and they understood the justification.

“I think if we’ve got justification, eventually we’ll start to see some of these hunting decisions be made similar to hoot-owl fishing restrictions. Our fishing community in the southwest side of Montana, they’ve gotten really good at understanding that when the temperatures get to this level and the flows get to this level, to protect the resource, we have to stop. We have to stop utilizing it,” Burrows said. “I think if we could take the same approach on the hunting side, sportsmen and sportswomen will accept it just like they do the fishing restrictions.

Hemorrhagic disease is not a risk to people, and meat from animals that appear healthy is safe to eat when properly cooked. Hunters should avoid killing or consuming animals that appear sick.

Contact reporter Laura Lundquist at lundquist@missoulacurrent.com.