1. Laboratory of Animal Behavior and Environmental Science; School of Agriculture; Meiji University; 1-1-1 Higashimita, Tama-ku Kawasaki Kanagawa 214-8571 Japan
2. Department of Animal Sciences; Teikyo University of Science; 2-2-1 Senju-Sakuragi, Adachi-ku Tokyo Japan
3. National Institute of Health Sciences; 1-18-1 Kamiyoga, Setagaya-ku Tokyo Japan