A horse's signature whinny comes from a combination of whistling and singing. The whinny is a unique combination of both high and low pitched sounds. The low tones come from vibration of tissue in the voice box. But what about the high ones? Scientists found the high notes stem from a whistle deep in the horses' voice boxes. That’s different from human whistling, which is made with the mouth. Horses are the only animals known to whistle while they sing. The two-toned whinnies could help them convey multiple messages. The new study was published Monday in the journal Current Biology.
