As summer vacation becomes a memory, and dreams of next year’s trip take shape, if that dream trip includes giraffes, be prepared to stay up late if you want to hear them talking.

Giraffes’ late night humming may, in fact, be a form of communication, researchers at the University of Vienna suggested. Their findings were published Sept. 9 in BMC Research Notes.

The researchers collected audio material from giraffes at three European zoos. Aside from the usual bursts, snorts, and grunts, there were harmonic, sustained, and frequency-modulated “humming” vocalizations.

“Based on the complex acoustic structure, these vocalizations might have the potential to convey...information on caller identity, size, strength, and motivation/arousal, [that is], …to mate or to fight,” Angela Stoeger-Horwath, PhD, and one of the paper’s authors, told NEWStat.