1. Kamogawa Sea World, 1464-18 Higashi-cho, Kamogawa, Chiba 296-0041, Japan
2. Primate Research Unit, Department of Biology, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand
3. Laboratory of Veterinary Physiology, Cooperative Department of Veterinary Medicine, Faculty of Agriculture, Tokyo University of Agriculture and Technology, Tokyo 183-8509, Japan
4. United Graduate School of Veterinary Sciences, Gifu University, Gifu 501-1193, Japan
5. International Marine Biological Research Institute, Kamogawa Sea World, 1464-18 Higashi-cho, Kamogawa, Chiba 296-0041, Japan