Giraffes are known to be quiet animals, and for a long time, it was believed that their necks were too long for them to produce sounds. However, recent research has shown that giraffes do make sounds, including low-frequency humming noises. The humming is a quiet vocalization that is within the range of human hearing, and it is believed to be a form of "contact call" between individuals who have been separated from their herd, helping them to find each other in the dark. The humming sound is also thought to be a way for giraffes to communicate with each other about their physical and motivational attributes. While giraffes are not known to make many other sounds, they may snort or hiss when threatened, and female giraffes may bellow to their young.