1. W.J. Severud Department of Veterinary Population Medicine, University of Minnesota, Saint Paul, Minnesota 55108 Present address: Department of Natural Resource Management, South Dakota State University, Brookings, South Dakota 57007
2. D. Wolfson Minnesota Cooperative Fish and Wildlife Research Unit and Department of Fisheries, Wildlife, and Conservation Biology, University of Minnesota, Saint Paul, Minnesota 55108
3. J. Fieberg Department of Fisheries, Wildlife, and Conservation Biology, University of Minnesota, Saint Paul, Minnesota 55108
4. D.E. Andersen U.S. Geological Survey, Minnesota Cooperative Fish and Wildlife Research Unit, Saint Paul, Minnesota 55108