Sage Grouse and WNV Fact Sheet

(current as of October 24, 2003)

How many sage grouse are known to have died from West Nile Virus in 2003?

19 in Wyoming
3 in Montana
5 in Alberta (Canada)

An additional eight carcasses from Montana and Wyoming collected this summer have also been submitted and are currently being analyzed at the Wyoming State Veterinary Laboratory in Laramie.

A county by county breakdown of WNV in sage grouse is as follows. In Wyoming, Big Horn Co. (1), Carbon Co. (1), Campbell Co. (13), Fremont Co. (1), Natrona Co. (1), Sheridan Co. (1), and Sweetwater Co. (1). In Montana, WNV-positive sage grouse have been found in Phillips Co. (2) and Big Horn Co. (1). The 5 WNV-positive sage grouse in Alberta were found in the southeastern portion of the province.

How was it determined that the birds were positive for WNV?

Each bird was tested for WNV using three different methods on three different kinds of tissues (usually brain, heart, and kidney): virus isolation, polymerase chain reaction (PCR) and immunohistochemistry (IHC).

Who found the dead birds?

They were found by researchers tracking radio-collared sage grouse on four different studies. Two studies are through the University of Montana, one is through the University of Alberta, and the fourth is being conducted by an environmental consulting firm..

Who funded those research studies?

The studies that found the WNV-positive sage grouse were funded by various provincial, state, and federal government agencies, universities, industry, and non-governmental institutions. Different studies were funded by different sources.

Is there a link between West Nile Virus and coal-bed methane development?

We don't know. That is just one of many possible explanations for the pattern of sage grouse mortalities observed that needs to be researched further.

How did government agencies in the U.S. respond to the information that sage grouse were dying of West Nile Virus?

The Bureau of Land Management and Wyoming Game and Fish Department immediately made this information public through press releases in August. Those two agencies, along with Montana Fish, Wildlife and Parks and the U.S. Fish and Wildlife Service also immediately increased monitoring efforts of radio-collared birds in both Montana and Wyoming and extended monitoring through the end of the mosquito season (typically early October). Monitoring efforts in Alberta were also extended in September. As a precautionary measure, Wyoming Game and Fish Department also closed the hunting season for sage grouse in three counties in northeastern Wyoming (Campbell, Sheridan, and Johnson counties).

How will WNV affect sage grouse populations across their range?

This is a brand new issue in sage grouse conservation and the effect that WNV will have on populations across their range is not yet known.

What is the current status of sage grouse?

Sage grouse are classified as a game species managed by state fish and game agencies. The USFWS is currently examining the merit of various petitions to list sage grouse in different parts of the country and range-wide.

Will finding WNV affect the listing of sage grouse under the ESA?

That determination will be made by the U.S. Fish and Wildlife Service at the appropriate time.

Details of the Powder River Basin study being done by The University of Montana that first found sage grouse
dying of WNV

The goals of the PRB study are to investigate the effect of coal-bed methane on sage grouse demographics (i.e., survival and reproduction), determine the ecological mechanisms underlying demographic effects, identify core breeding, brood-rearing, and wintering habitats, and make recommendations to help the BLM and energy industry avoid negative impacts to sage grouse and their habitat. They are working closely with the BLM, state fish and game agencies in Montana and Wyoming, and the coal-bed methane industry. They were working on three study sites: two sites in southeastern Montana have no coal-bed methane development and one site in northeastern Wyoming has extensive coal-bed methane development.

The major cause of mortality at the coal-bed methane site near Spotted Horse, Wyoming was West Nile Virus. At that site, they lost 6 of 8 adult hens to West Nile Virus during a two-week period at the end of July and beginning of August. Among 42 radio-collared hens monitored at the two sites without CBM development, only one WNV mortality has been detected so far. However, three carcasses from those sites are still being tested.

It's unclear whether sage grouse are resistant to the virus. The researchers on the PRB study collected blood samples from 49 live sage grouse in August and September and will be able to answer that question once the laboratory results are in.
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