BLM-MT, West Nile Virus Threats Surveillance in the Sagebrush Focal Area of North Central Montana, HiLine/Central Districts

Background: Due to the signing of the Record of Decision for the HiLine Resource Management Plan and the Lewistown Sage Grouse Amendment in September 2015, Montana/Dakotas Bureau of Land Management (BLM) designated a Sagebrush Focal Area (SFA) in Valley, Phillips, Petroleum and Fergus Counties. This designation recognizes the high quality sage grouse habitat that exists in these areas. There are nearly 1.87 million surface acres administered by the following BLM field offices within the SFA: Glasgow Field Office (994,398 ac.), Malta Field Office (638,575 ac.) and Lewistown Field Office (233,219 ac.) West Nile virus (WNv) has been identified as a potentially significant stressor on Greater sage-grouse (GSG) populations across the west. WNv outbreaks have been identified in Montana and specifically in the SFA. In 2015, the Glasgow Field Office partnered with Universities to pilot WNv surveillance in Valley County. Existing seasonals were able to conduct the trapping operations in addition to their assigned work. The Universities then tested samples for WNv. The results of this project revealed that Culex tarsalis (Ct) is produced in high densities across the portion of the SFA that was sampled. No WNv was found in the collections in 2015. This project will benefit GSG in the SFA by enabling the development of a threats model and determination of the most productive water body-type for breeding Ct. The threats model will further develop an existing statewide model developed by the universities. This project will focus and refine the model for the SFA, highlighting key areas that are most productive for the production of Ct. This information will drive future management actions that would attempt to control mosquito production in key sage-grouse areas. Such actions could include the development of reservoir storage and release procedures, removal of water structures that promote Ct production, installation of livestock watering features that do not promote Ct breeding, and the use of vegetative treatments and biological controls in wetlands. Objectives: To develop a WNv surveillance and research project. This study will provide annual assessments of prevalence for this virus in the newly designated SFA in Montana. The WNv, carried by the Ct mosquito, has been recognized as a serious threat to GSG populations and is one threat that is not currently being monitored by the BLM or any other agency in the SFA. This research could lead to the identification of management actions that will benefit GSG by minimizing Ct breeding conditions. In addition to surveillance, the research component of this work will evaluate the breeding potential of Ct in relation to various water developments that the BLM currently builds or has built on the landscape for livestock. These water developments include large reservoirs, waterfowl breeding ponds and livestock watering pits. This research will seek to determine which developments are more or less likely to produce the conditions that increase or decrease Ct breeding. This research will enable land managers and the public to evaluate and construct water developments that minimize habitat for Ct. This project will provide the knowledge, through the model, to identify areas in the SFA that are at the highest risk of a WNv outbreak due to elevated production of Ct. In addition, this project will identify which livestock water developments and other water bodies are most likely to produce Ct, the species of mosquito that carries WNv. This will provide the scientific guidance to help outline Best Management Practices pertaining to water development projects that will benefit GSG. Public Benefit: Utilization of the knowledge that results from this work would improve GSG and land management decisions by minimizing breeding habitat for Ct and decreasing the threats of WNv. Improved early warning of WNv outbreaks for agencies and private landowners in areas where surveillance will occur.