நன்றி சொல்ல வேண்டும் . Sounds bordering infrasonics and ultrasonic could be heard not by human ears but snakes, horses, dogs and birds get easily alerted in those frequencies. Before human could sense the oncoming of storm, solar eclipse, Aandhi , tsunami et al. A storm brewing at 600miles north of south America sensed by third generation of Monarch butterflies returning from southern hills caused them to change to a long diversionary route. Google to get more info. Regards.