Post by Dutch on Apr 29, 2018 8:33:36 GMT -5
naturalpursuitoutdoors.blogspot.com/2018/04/west-nile-virus-is-lead-suspect-in.html?m=1
West Nile Virus is a lead suspect in ruffed grouse decline
BY TYLER FRANTZ
There are few outdoor experiences more thrilling than flushing a ruffed grouse from dense mountain cover. Unfortunately, upland hunters have felt this rush at a diminishing rate over the past three decades - a cause for concern among many.
Pennsylvania Game Commission biologist Lisa Williams said ruffed grouse populations have been declining since 1981, with the early 2000’s serving as a record low tipping point, followed by a brief recovery and another drop in numbers based on fall flush reports and summer brood surveys. She believes mosquitoes are the root of the problem.
“In studying the population reports, I recognized a problem similar to White-Nosed Syndrome in bats, which got me thinking about diseases vs. habitat decline,” Williams explained. “Then I realized the timing was right for West Nile Virus (spread by mosquitoes), which arrived in 1999 in New York City. By 2000, it had spread to southern New England states, and in 2002, every county in Pennsylvania had it. West Nile Virus (WNV) is primarily a bird disease, so I suspected it might be impacting our grouse.”
In 2015, Williams spearheaded a challenge study to determine if ruffed grouse were susceptible to WNV. Wild Pennsylvania grouse eggs were propagated and sent to Colorado State University where chicks were inoculated with WNV to test the results.
Forty-percent died in the first week. Forty- to fifty-percent survived longer but had severe organ damage such as weakened heart tissue and brain matter. Alarmingly, only 10-percent survived, yielding a 90-percent mortality rate in a controlled lab setting.
It was clear: WNV spelled bad news for grouse.
These findings seemed to match field surveys where June production was rising, but July survival and subsequent fall flush rates were not good. Seeing that WNV season really kicks off in mid summer, it was entirely plausible that young chicks were being bitten by mosquitoes, contracting the virus, and dying before they had a chance to reach maturity.
Williams asked Pennsylvania grouse hunters to collect blood samples of fall-harvested birds, and of the 400-plus samples received, close to 20-percent included antibodies to West Nile Virus. Of course, this sample cohort only represented the birds that survived from the summer, not those that already perished. But some had been bitten and made it.
This led to the WNV Surveillance in Grouse Habitat Study during the summer of 2017 in cooperation with the Pennsylvania Department of Environmental Protection.
“We sought to determine which mosquitoes were most likely to transmit West Nile Virus,” Williams said. “Essentially, mosquito traps were set in prime grouse habitat, and 25 different species of mosquitoes were collected. These specimens were then tested for WNV. One type, Culex Restuans, accounted for up to one-fourth of all positive tests.”
“We then asked ourselves, what landscape variables are associated with this species? We originally thought ideal brood habitat, prior to 2015, was low lying moist bottomlands with abundant ground cover, but now we’re not so sure,” Williams explained.
It was determined that elevation correlates with the presence or absence of Culex Restuans with the magic number being around 1,200 feet. As a result, efforts are now being focused on active forest management in higher elevations to help the state’s remaining grouse population to out-persist the fatal effects of WNV. Ongoing habitat restoration in these areas has already begun.
“Grouse do better in good habitat,” Williams said. “They need abundant habitat (high quality cover, with different age classes of growth, close together with abundant food year-round) on 15-percent of the landscape. Pennsylvania is currently at seven-percent of the landscape, coming up about 800,000 acres short.”
“Our best grouse habitat is in the northern hardwoods located in the upper 1/3 of the state, and we see populations outperforming the Oak-Hickory forests of the lower 2/3 of the state. If it weren’t for WNV, these should be the boom days of grouse in the northern tier, but it’s not just as simple as cut a tree, save a grouse.”
Williams said a responsive harvest framework is also important to maintain a goal of sustainable hunting, while still harvesting surplus animals that might die over the winter.
WNV mortality occurs before the hunting season, and 2015-16 surveys showed 51,000 grouse were harvested, with about 10,000 of them being WNV survivors. Given a generous survival rate of 30- to 50-percent, that would mean ten- to thirty-thousand birds died before the season began. With this in mind, Williams developed a harvest framework based on fall flush rates, summer brood surveys, and WNV surveillance data.
Taking all data into account, she determines if it is a good survival year and adjusts the hunting season length accordingly. This is the reason for cancelling the winter season for the past two years. Though it means less opportunity, 72-percent of hunters who contacted the PGC last year voiced support of the late-season closure.
“Grouse in Pennsylvania are in a pretty precarious place right now,” Williams said. “But if any state is going to turn this around for them, it makes sense for Pennsylvania to try.”
For more great writing, photography and video work by outdoors freelancer, Tyler Frantz, visit www.naturalpursuitoutdoors.com. Also, please LIKE US ON FACEBOOK!
West Nile Virus is a lead suspect in ruffed grouse decline
BY TYLER FRANTZ
There are few outdoor experiences more thrilling than flushing a ruffed grouse from dense mountain cover. Unfortunately, upland hunters have felt this rush at a diminishing rate over the past three decades - a cause for concern among many.
Pennsylvania Game Commission biologist Lisa Williams said ruffed grouse populations have been declining since 1981, with the early 2000’s serving as a record low tipping point, followed by a brief recovery and another drop in numbers based on fall flush reports and summer brood surveys. She believes mosquitoes are the root of the problem.
“In studying the population reports, I recognized a problem similar to White-Nosed Syndrome in bats, which got me thinking about diseases vs. habitat decline,” Williams explained. “Then I realized the timing was right for West Nile Virus (spread by mosquitoes), which arrived in 1999 in New York City. By 2000, it had spread to southern New England states, and in 2002, every county in Pennsylvania had it. West Nile Virus (WNV) is primarily a bird disease, so I suspected it might be impacting our grouse.”
In 2015, Williams spearheaded a challenge study to determine if ruffed grouse were susceptible to WNV. Wild Pennsylvania grouse eggs were propagated and sent to Colorado State University where chicks were inoculated with WNV to test the results.
Forty-percent died in the first week. Forty- to fifty-percent survived longer but had severe organ damage such as weakened heart tissue and brain matter. Alarmingly, only 10-percent survived, yielding a 90-percent mortality rate in a controlled lab setting.
It was clear: WNV spelled bad news for grouse.
These findings seemed to match field surveys where June production was rising, but July survival and subsequent fall flush rates were not good. Seeing that WNV season really kicks off in mid summer, it was entirely plausible that young chicks were being bitten by mosquitoes, contracting the virus, and dying before they had a chance to reach maturity.
Williams asked Pennsylvania grouse hunters to collect blood samples of fall-harvested birds, and of the 400-plus samples received, close to 20-percent included antibodies to West Nile Virus. Of course, this sample cohort only represented the birds that survived from the summer, not those that already perished. But some had been bitten and made it.
This led to the WNV Surveillance in Grouse Habitat Study during the summer of 2017 in cooperation with the Pennsylvania Department of Environmental Protection.
“We sought to determine which mosquitoes were most likely to transmit West Nile Virus,” Williams said. “Essentially, mosquito traps were set in prime grouse habitat, and 25 different species of mosquitoes were collected. These specimens were then tested for WNV. One type, Culex Restuans, accounted for up to one-fourth of all positive tests.”
“We then asked ourselves, what landscape variables are associated with this species? We originally thought ideal brood habitat, prior to 2015, was low lying moist bottomlands with abundant ground cover, but now we’re not so sure,” Williams explained.
It was determined that elevation correlates with the presence or absence of Culex Restuans with the magic number being around 1,200 feet. As a result, efforts are now being focused on active forest management in higher elevations to help the state’s remaining grouse population to out-persist the fatal effects of WNV. Ongoing habitat restoration in these areas has already begun.
“Grouse do better in good habitat,” Williams said. “They need abundant habitat (high quality cover, with different age classes of growth, close together with abundant food year-round) on 15-percent of the landscape. Pennsylvania is currently at seven-percent of the landscape, coming up about 800,000 acres short.”
“Our best grouse habitat is in the northern hardwoods located in the upper 1/3 of the state, and we see populations outperforming the Oak-Hickory forests of the lower 2/3 of the state. If it weren’t for WNV, these should be the boom days of grouse in the northern tier, but it’s not just as simple as cut a tree, save a grouse.”
Williams said a responsive harvest framework is also important to maintain a goal of sustainable hunting, while still harvesting surplus animals that might die over the winter.
WNV mortality occurs before the hunting season, and 2015-16 surveys showed 51,000 grouse were harvested, with about 10,000 of them being WNV survivors. Given a generous survival rate of 30- to 50-percent, that would mean ten- to thirty-thousand birds died before the season began. With this in mind, Williams developed a harvest framework based on fall flush rates, summer brood surveys, and WNV surveillance data.
Taking all data into account, she determines if it is a good survival year and adjusts the hunting season length accordingly. This is the reason for cancelling the winter season for the past two years. Though it means less opportunity, 72-percent of hunters who contacted the PGC last year voiced support of the late-season closure.
“Grouse in Pennsylvania are in a pretty precarious place right now,” Williams said. “But if any state is going to turn this around for them, it makes sense for Pennsylvania to try.”
For more great writing, photography and video work by outdoors freelancer, Tyler Frantz, visit www.naturalpursuitoutdoors.com. Also, please LIKE US ON FACEBOOK!
