September 8, 2004
West Nile hits already troubled sage grouse
By Kevin Woster, Rapid City (SD) Journal
The West Nile virus is emerging as a formidable threat to the sage grouse, an increasingly rare native bird that inhabits parts of western South Dakota and is fast disappearing across the entire American West.
Field observations and laboratory tests in Wyoming and Montana have confirmed that sage grouse are especially susceptible to West Nile, showing limited, if any, resistance to the disease so far. That news worries John Wrede of Rapid City, who coordinates sage grouse study and management for the state Game, Fish & Parks Department.
"It has been demonstrated through laboratory inoculation of West Nile, that if sage grouse get it, even in the remotest dose, they die. They're history," Wrede said. "There's no doubt about it. This is a big threat to this species."
The species already faces many other threats, including habitat loss from livestock grazing, wildfire, mining, oil and gas development, road construction and vehicle-related recreation, as well as the spread of invasive noxious weeds and, in certain areas, hunting pressure.
Now, West Nile has been added to the list of threats to a bird that some conservationists already want added to the threatened or endangered species list — a move that has so far been unsuccessful.
"Yes, disease, and predominantly West Nile, is on the radar screen," Wrede said.
GF&P has tested blood and tissue samples from the few sage grouse taken during the limited sage grouse season, which is open for only two days a year in Butte and Harding counties only. Hunters in the season are allowed to take only one sage grouse each.
Last year, 34 hunters shot 12 sage grouse, 10 of which were tested for West Nile. They all tested negative.
Surveys this year on 15 known breeding areas — called leks — in Harding and Butte counties showed a 44 percent increase in the number of male grouse on the leks. But Wrede said that rise was probably simply a periodic spike in the continuing downward trend in South Dakota.
Such spikes tend to come about every 10 years, but then are lost, Wrede said.
And even with an increase this year, it's likely that there are fewer than 750 sage grouse in the state, Wrede said. Almost all of those birds are in Butte and Harding counties, although a few have been reported in Fall River County and even Meade County, Wrede said.
Sage grouse numbers have slipped in South Dakota since record keeping began in the 1970s. Since 1990, bird numbers have fallen by 25 percent, he said. The decline has been even worse — more than 40 percent — since 1960 across the 11 Western states and two Canadian provinces that compose the historic range of the sage grouse.
Some estimates indicate that sage grouse populations could have declined by as much as 86 percent from their historic levels.
The birds — which can be twice the size of a ring-necked pheasant and engage in dramatic spring courtship rituals — rely almost entirely on sagebrush for food, shelter and escape cover from predators. Suitable sagebrush habitat was limited in South Dakota to begin with and has declined with human activity and development.
But the loss of sagebrush has been even greater in states where it had been a dominant plant species. Federal and state resources agencies have been working on plans to preserve and even restore sagebrush habitat and stem the declines in the sage grouse population.
Now that work could be further complicated by the spread of West Nile virus, a nasty newcomer to the Great Plains that infects a variety of wildlife species as well as human beings. Birds can be particularly susceptible, although certain species — including turkeys and ring-necked pheasants — appear more resistant than others.
The sage grouse seems to be among the least resistant. Wildlife researchers in Wyoming and Montana began noticing that in 2003 and 2004, Wrede said.
Sage grouse fitted with radio-transmitter collars got sick and died of what was later confirmed as West Nile, he said.
"They started winding up with dead radio-collared birds," Wrede said. "Before they knew it, only two of the 13 birds they'd radio collared were left. Then, the red flags went up, and they started looking."
Wrede said it was unclear whether and how well the sage grouse would develop resistance to the disease, something that other birds already appear to have done. But the virus adds another obstacle in the coordinated effort to assure the future of sage grouse.
Wrede hopes the state sage grouse hunting season, re-established on a very limited basis in 2002, will help biologists collect data to monitor the birds, their population levels and their health in South Dakota.
"With each season, we learn more about the population structure and distribution of the birds," he said. "The more we learn about them the better."
Contact Kevin Woster at 394-8413 or firstname.lastname@example.org
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