The effectes of regulated lake levels of beaver in Voyageurs National Park, Minnesota
Smith DW and Peterson RO. 1988. The effectes of regulated lake levels of beaver in Voyageurs National Park, Minnesota. Research/Resources Management Report. MWR-11. Research and Science Division, Midwest Regional Office, National Park Service, U.S. Department of the Interior. Omaha, Nebraska
Beavers in Voyageurs National Park were studied to determine the effects of a winter water drawdown of 2 meters (3 meters annually) behind hydroelectric dams. Several areas of differing environmental conditions were chosen for study based on water drawdown (present, slight, absent) and habitat conditions. Beaver lodges were counted from aircraft, and beavers were live trapped and radio implanted to examine the effects of drawdowns and vegetation on beaver distribution, abundance, mortality, and reproduction. Active beaver lodge density was greatest on the drawdown lake Kabetogama, and was increasing at a higher rate on Kabetogama than on the slight drawdown lake Rainy. Beavers living in the drawdown environment abandoned their lodges overwinter, but stayed in the lodge vicinity. Food cache utilization and usage of aquatic vegetation was less in the drawdown areas. Above-ice foraging in winter and spring abandonment of the fall-winter homesite was more common in the drawdown environment. Family size and kit production were lower in the drawdown and poor habitat locations, and adult body size was less at the poor habitat location. Costs to beavers living in the drawdown environment were estimated. Variability and low sample sizes obscured interpretations, but beavers living in the drawdown environment came through winter in poorer condition. Winter drawdown was hypothesized to interfere with reproductive behavior. Overwinter mortality was not widespread, but some did occur due to starvation. Springtime wolf predation due to low water levels was thought to be the major beaver mortality factor, but estimated not to exceed 25%. Beaver-forest relations were also discussed. Management recommendations were to change water management to approximate a more natural fluctuation. Total yearly fluctuation should not exceed 1.5 meters, and winter drawdowns should not exceed 0.7 meters.
- Type
- Published Report
- Authors
- Smith, D; Peterson, R
- Date of Issue
- 1988-07
- Publisher
- Research and Science Division, Midwest Regional Office, National Park Service, U.S. Department of the Interior
- Units
- VOYA , WRD
- Keywords
- Animal Studies, Clemson, Habitat Selection, Mammals, Water Level, Water Quantity, Wildlife habitat improvement, Wildlife Monitoring