1. Department of Ecology, Evolution and Behaviour University of Minnesota 140 Gortner Laboratory, 1479 Gortner Avenue St. Paul MN 55108 U.S.A.
2. Department of Fisheries, Wildlife and Conservation Biology University of Minnesota 135 Skok Hall, 2003 Upper Buford Circle St. Paul MN 55108 U.S.A.
3. Department of Veterinary Population Medicine University of Minnesota 225 Veterinary Medical Center, 1365 Gortner Avenue St. Paul MN 55108 U.S.A.