Giraffes hum, but only in the dark

Wired : Although giraffes have been heard to snort on occasion, most giraffe keepers and zoo managers were convinced that giraffes don’t vocalize like other animals. Researchers proposed that the reason might be the animals’ long necks. Either they can’t produce enough airflow through their trachea and larynx to emit any sounds or the sounds they emit are at too low a frequency for humans to hear. Now researchers at the University of Vienna say giraffes do indeed vocalize: They hum at night . The researchers’ findings are based on eight years of recording giraffes at three zoos. By visually examining the frequency patterns of more than 938 hours of giraffe sound recordings, the researchers found that the animals hum at about 92 Hz—similar in sound to a human snoring—and only after dark. What they are saying to each other, however, is still unknown. To determine that, scientists will need to use high-level night-vision instruments to match the sounds to what the giraffes are doing.