1. Laboratory of Companion Animal Behavior and Wildlife Ecology, Department of Veterinary Science, School of Veterinary Medicine, Rakuno Gakuen University, Hokkaido, Japan
2. Small Animal Clinical Sciences, Department of Veterinary Medicine, Rakuno Gakuen University, Hokkaido, Japan
3. Central Fisheries Research Institute, Fisheries Research Department, Hokkaido Research Organization, Hokkaido, Japan
4. Veterinary Anatomy, Department of Veterinary Medicine, Rakuno Gakuen University, Hokkaido, Japan