1. Department of Environmental Veterinary Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Kita 18 Nishi 9, Kita-ku, Sapporo, Hokkaido 060-0818, Japan
2. Noboribetsu Bear Park, 224 Noboribetsuonsencho, Noboribetsu, Hokkaido 059-0515, Japan
3. Department of Clinical Sciences, Division of Veterinary Medicine, Faculty of Veterinary Medicine, Hokkaido University, Kita 18 Nishi 9, Kita-ku, Sapporo, Hokkaido 060-0818, Japan
4. Department of Clinical Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Kita 18 Nishi 9, Kita-ku, Sapporo, Hokkaido 060-0818, Japan
5. Shiretoko Nature Foundation, 531 Iwaubetsu, Shari, Hokkaido 099-4356, Japan
6. Department of Environmental Veterinary Sciences, Division of Veterinary Medicine, Faculty of Veterinary Medicine, Hokkaido University, Kita 18 Nishi 9, Kita-ku, Sapporo, Hokkaido 060-0818, Japan