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West Nile Virus Found In Wisconsin Ruffed Grouse

Scientists Unsure Whether Disease Is Impacting Bird's Population

ruffed grouse
Seabamirum (CC-BY)

West Nile virus has been discovered for the first time in Wisconsin’s ruffed grouse population. According to the Wisconsin Department of Natural Resources, three out of 16 birds submitted by hunters for annual monitoring of sick and dead birds have tested positive for the virus.

The ruffed grouse were collected from northern Wisconsin in Ashland and Douglas counties. One tested positive for West Nile virus while two tested positive for both West Nile and Eastern equine encephalitis virus.

West Nile virus, which originated in Africa, was first detected in Wisconsin in 2002. More recently, the mosquito-borne disease has prompted concern among hunters. In 2017, they harvested 185,336 ruffed grouse, which was the lowest harvest in more than three decades.

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The decline has some worried that West Nile virus may be to blame. Despite the discovery, DNR upland wildlife ecologist Mark Witecha said it’s too early to tell whether the ailment is hurting the bird’s population.

“All this states is that grouse in Wisconsin have been exposed to West Nile virus, but we can’t certainly draw any conclusions about prevalence or impacts of the disease from just this effort,” he said.

The state has been testing “opportunistically” for the virus, but Witecha said they received only eight ruffed grouse submissions for sampling between 2002 to 2017. The cause of the bird’s recent decline remains uncertain, but the population of ruffed grouse normally swings every 10 years.

“The decline came before we expected it basically so that’s what kind of raised some of the concerns,” Witecha said.

The impact of the virus on ruffed grouse is difficult to determine. However, Witecha said the disease has been extremely deadly in species like crows and bluejays.

“With other species like turkeys, it doesn’t seem to have an impact whatsoever,” he said.

Brent Rudolph, director of conservation policy with the Ruffed Grouse Society, said Wisconsin, Michigan and Minnesota are partnering in a three-year study to better understand how the disease is impacting ruffed grouse across the region.

“It’s going to be really hard to understand with a lot of confidence what’s happening and certainly in an individual county or area within a state, but by coordinating across the region it should help us a little bit better understand what might be some of the factors that drive higher prevalence, higher exposure to West Nile across the three states that have, obviously, a number of similarities, but also differences in their habitat and grouse numbers and hunter distribution and so forth,” Rudolph said.

Rudolph said each of the three states have somewhere between 70,000 to 90,000 hunters that pursue ruffed grouse. He added the bird is an indicator species on forest health and its ability to provide adequate habitats for wildlife.

The Wisconsin DNR distributed 500 sampling kits to hunters last fall. Hunters returned 238 samples, which have been sent to a lab in Georgia for testing. Witecha said they expect to have preliminary results by this summer.