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Spring 2005 A Boon for Business: Incubator nurtures homegrown companies Antibody Buildup: University lab explores Libby health issue Space Man: New UM researcher probes the solar system for NASA Core Issues: Flathead Lake research reveals secrets in sediment Lords of the Prairie: Investigating the links among sage grouse, West Nile virus and energy development
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Lords
of the Prairie
Before sunrise the females swoop in. First one, then another — wings slicing the air with a buzz like a small fighter jet. Meanwhile, not far away, a male “blurps” in the darkness. And so it has passed every spring in the wide-open sagebrush sea of the interior West for millennia: mating season for the greater sage grouse. Like the seasonal displays of so many other birds, sage grouse courtship is nothing short of a spectacle. The grouse gather at “leks” — clearings in the sagebrush where generations of birds return year after year to breed. While there, male grouse strut by extending their pointed feathers skyward, expanding the yellow air sacs hidden behind brilliant white chest feathers and then making a popping sound by forcing air from their sacs. The puffery is meant to impress females and warn off lesser males. As morning light from the rising sun illuminates the birds, it’s clear that only one dominant male who occupies the center of the lek has earned the affections of his female counterparts. The dominant male will breed with 80 percent of all the females that attend his lek; lesser males will have to earn this right in subsequent years.
UM wildlife biology Professor Dave Naugle says the annual grouse gathering isn’t what it used to be. Sage grouse depend on a healthy and expansive sagebrush habitat for both food and shelter. A wide variety of factors contributed to their long decline — from clearing sagebrush for grazing to development of roads and cities to the introduction of invasive plants. “Previously widespread, sage grouse no longer exist in about half of their original range in western North America,” Naugle says, “with an estimated range-wide population decline of 45 to 80 percent and local declines of 17 to 92 percent.” Despite these declines, the U.S. Fish and Wildlife Service recently decided against protecting the greater sage grouse under the Endangered Species Act. In 2003 the Bureau of Land Management asked Naugle, who teaches in UM’s College of Forestry and Conservation, to explore the potential impact of a new kind of change to the grouse’s sagebrush landscape — booming coalbed natural gas development in northeast Wyoming and southeast Montana — which happen to be one of the birds’ remaining strongholds. Any findings that could potentially slow energy development in the West are automatically politically contentious, and the BLM looked to Naugle to lead an independent and thorough investigation.
In July 2003, after many other sage grouse researchers were wrapping up their summertime field work, Naugle’s team continued tracking radio-marked birds. Their work led to a disturbing discovery. Brett Walker, a UM doctoral candidate and one of Naugle’s students, called on his truck phone to say he had walked up to a grouse that seemed sick. After about 15 minutes the bird was dead. Walker wondered if the bird died of West Nile virus, which is sweeping the West. Testing of the carcass at the Wyoming State Veterinary Laboratory indicated his hunch was right. That year, Naugle and his colleagues found that West Nile virus killed 25 percent of all radio-marked sage hens in four populations in Wyoming, Montana and Alberta, Canada. In 2004 the virus spread further, killing an additional 10 percent of radio-marked females in Colorado, California, Wyoming and Montana. “Right now, West Nile is sweeping across North America,” Naugle says. “We’ve found a species that’s very susceptible.”
Despite continued testing of live and hunter-harvested sage grouse since 2003, Naugle’s team has yet to find an individual resistant to the disease. And when wild sage grouse were challenged with West Nile virus in the laboratory, they all died. The greater sage grouse was added to a growing list of North American creatures — including 228 bird species — identified as carriers of the West Nile virus. Naugle says part of the bird’s vulnerability to the disease is related to the survival strategy the species has developed over time. Unlike similar birds such as bobwhite quail or ring-necked pheasants, sage grouse typically live a long time and have small clutch sizes. Instead of having a large number of young that seasonally boost the population, the birds depend on their ability to survive and reproduce for many years. Since Walker stumbled upon that first dying sage grouse, researchers have tried to answer questions about the complexities of the disease, its impact on grouse and possible connections to the coalbed natural gas industry. Naugle has two doctoral students working with him and about a dozen undergraduates helping in the field. Funding comes from a variety of sources, including industry groups, private conservation charities and government sources. In addition, researchers from the University of Wyoming, Montana State University and government agencies are cooperating to learn more. A primary host of the virus seems to be one of 42 species of mosquito found in the West — Culex tarsalis. Tarsalis reproduces in natural and man-made water sources throughout the West — and this particular bloodsucker feeds primarily on birds. Sage grouse are at risk because females and their young congregate around water where food is plentiful in late-summer.
While Naugle is careful to point out a multitude of factors in the decline of sage grouse over time, West Nile virus and its potential connection to coalbed natural gas development adds a whole new infectious disease angle to attempts at conservation. The natural gas extraction process brings millions of gallons of groundwater to the surface and stores it in man-made ponds. Naugle and his colleagues found that these ponds are significant producers of Culex tarsalis. Researchers now have partnered with industry to demonstrate how to build ponds that are less conducive to mosquito production. Naugle’s lab recently received a grant to investigate ways in which West Nile virus is able to persist in the environment. “We have isolated DNA from stomachs of blood-fed mosquitoes to identify host species that contract the disease but do not die from it.” Understanding the host dynamics of this disease brings Naugle and his staff one step closer in their quest to develop effective management strategies to safeguard one of America’s greatest spectacles — the spring dance of the sage grouse. |
Rita
Munzenrider, Director |
