Bat hibernacula in the karst landscape of central Manitoba : protecting critical wildlife habitat while managing for resource development

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Bilecki, Lori C.
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The Grand Rapids uplands in central Manitoba is a karst area of intense resource development. Current activities include timber extraction, mineral exploration, a hydro-electric generating station, established and potential hydro-electric transmission lines. Significant features of this karst landscape include 60 known caves, 11 of which provide critical over-wintering habitat for two species of bats, Myotis lucifugus and Myotis septentrionalis and possibly Eptesicus fuscus. The issue that I addressed was how to protect critical wildlife habitat while managing for profitable resource management. Little information existed prior to this study about the bat hibernacula in central Manitoba. Therefore, baseline temperature and relative humidity data were collected every six hours from October 16, 1999 to May 28, 2000 from four bat hibernacula: Firecamp, Iguana Crypt, Microwave and Cutters Cave. Bat activity was also monitored in each cave over the same time period. Cave temperatures were not constant throughout the winter, and were found to be lower than the anticipated mean temperature of 4-5 oC. The overall mean temperature of Cutters Cave was 1.1 oC, Firecamp was 1.7 oC, Microwave was 2.1 oC and Iguana Crypt was the warmest at 4.8 oC. These overall mean temperatures were found to be significantly different using Duncan's Multiple Range Test. The relative humidity sensors may have become saturated, recording questionable readings of relative humidity above 100%. However, the accuracy of the logger was only 4%. The overall mean relative humidities were calculated to be 96% in Firecamp, l00% in Microwave, 103% in both Iguana Crypt and Cutters Cave. The Wildlife Branch of Manitoba Conservation issued Bat Hibernacula Management Guidelines in 1996. These guidelines were reviewed during this study and compared with guidelines for karst, caves or bat hibernacula from British Columbia, Alberta, Ontario, Quebec, New Brunswick, Missouri and Alaska. Once a review of these guidelines was completed, best management practices were determined and recommendations made to government, industry and other stakeholders. Best practices include undertaking a karst management plan for the Grand Rapids area, including a cave inventory and classification system where bat hibernacula would be classified as sensitive habitat. Appropriate management guidelines should be prescribed by an interdisciplinary management committee, which may include prohibiting resource development above or near bat hibernacula (i.e. removed from the commercial land base) as recommended by the BC Ministry of Forests and Alaska Forest Service. The current operating practices of Tolko Industries Ltd., Manitoba Hydro and Falconbridge Ltd. were also reviewed. Currently, only Tolko Industries Ltd. has specific guidelines for working near bat hibernacula, but these are not consistent with guidelines recommended by Manitoba Conservation. Resource developers should endeavor to implement all provincial guidelines. However, in order to ensure protection of karst features such as caves (especially bat hibernacula) Manitoba Conservation should ensure these guidelines are implemented by including them in work permits under The Crown Lands Act and/or drafting them as regulations under the appropriate statute.