Ruffed grouse hit by West Nile Virus

As a rule, ruffed grouse hunters don’t expect a bird in the bag every time out.

The supremely wild birds typically fly well ahead of hunters. And once airborne, the feathered rockets are extremely challenging to hit. Successful grouse hunts are often measured by flushes heard, not birds killed.

Such metrics may need to be further modified if a disease scare proves to be true.

West Nile Virus had been confirmed in ruffed grouse, officials in Michigan announced Monday, the first such findings in that state.

Five birds collected from August through October, including two found dead and three shot by hunters, were determined to be WNV-positive in testing at the Michigan Department of Natural Resource’s Wildlife Disease Laboratory in Lansing.

Three of the WNV-positive grouse were from the Upper Peninsula, according to the MDNR.

The findings follow research started in 2014 by the Pennsylvania Game Commission to study the effects of the virus on ruffed grouse. The Ruffed Grouse Society was a partner in the project.

Wildlife biologists with the PGC collected wild grouse eggs in spring in Pennsylvania and, working with a facility in Idaho, exposed some of them to WNV. Hunter-killed grouse in the Pennsylvania were also tested for the virus.

After two years of work, the important questions were answered. “WNV clearly kills ruffed grouse and as many as 80% of grouse exposed to the virus are killed outright or might have reduced survival,” wrote Lisa Williams, PGC game birds biologist, in a Sept. 2016 article in “Game News.”

Among grouse killed by hunters in Pennsylvania, 13% were positive for WNV antibodies. The disease was found in every county in the state.

The study provided good and bad news. Some grouse survived exposure to the virus and developed antibodies to it. But others, perhaps many, were killed by the disease.

The grouse news from Michigan and Pennsylvania is especially compelling this year to hunters, bird watchers and wildlife managers in Wisconsin.

Ruffed grouse populations in the Upper Midwest typically follow a 10-year cycle, reaching lows in years ending in “4” or “5” and highs in years ending in “8” or “9,” according to RGS biologists.

But this fall, many hunters in Wisconsin were asking: “What’s wrong?” and “Where are they?”

Field reports from hunters in the Upper Midwest were confirmed by results at the RGS national hunt held in October in Grand Rapids, Minn. Hunters at the event harvested an average of 0.5 grouse per day, lowest in the 36-year history of the event.

Could it be WNV?

The disease has not been documented in ruffed grouse in Wisconsin, according to the state Department of Natural Resources. But only eight grouse have been tested for WNV in Wisconsin (seven from 2002-’04, one in 2008); all were negative.

It’s possible the disease is just now impacting grouse in northern Wisconsin, Minnesota and Upper Michigan.

The virus affects more than 250 species of wildlife, as well as humans and horses. Among the species most affected are crows and jays. But it’s now clear WNV also kills grouse.

“It’s very difficult to say West Nile Virus has reduced ruffed grouse populations, since the birds are relatively secretive and it’s so hard to get enough samples,” said Dan Grear, wildlife disease specialist at the U.S. Geological Survey’s National Wildlife Health Center in Madison.

West Nile Virus is a viral disease that was commonly found in Africa, Europe, the Middle East and West Asia. It first appeared in New York in 1999 and quickly spread throughout North America. It was first detected in Wisconsin in 2001. West Nile Virus is primarily transmitted to humans through the bite of infected mosquitoes. Most people infected with the virus do not show symptoms.

Interestingly, the number of WNV cases in humans is up this year in Wisconsin, according to data from the state Department of Health Services.

So far in 2017, 41 cases of WNV had been reported in humans, resulting in three deaths, compared to 13 cases and no fatalities in 2016.

An average of 17 cases per year were documented in Wisconsin from 2002’16. The highs were 57 in 2012 and 52 in 2002.

This year, then, will have at least the third-highest number of human cases of WNV in Wisconsin in the last 16 years, and will be about 2.5 times greater than the average.

With the Wisconsin DNR undergoing staff and budget reductions, as well as the loss of its science services division, a state-specific study on diseases in ruffed grouse may not be in the cards.

But it would be wise to consider the work done in Michigan and Pennsylvania and expect at least some WNV impact on Wisconsin grouse.

The spread of a disease such as WNV among wildlife is notoriously difficult to curb. But habitat improvement, especially in the name of one of Wisconsin’s iconic native species, is a worthy and attainable goal.