Duet of "Singing" Gibbons at Brookfield Zoo

Check your sound levels before you watch this video of a gibbon "duet" as Indah and Benny call out to each other at Brookfield Zoo! (Their male offspring Thani is listening in!) Mated pairs of gibbons mark their territory primarily through loud vocal displays, the sounds of which travel hundreds of yards through the forest. To strengthen the bond between them, male and female gibbons perform a sort of duet. The females' part is a long rising series of notes that end in a fast "twitter." The male's song is not as complicated as the female's. He grunts, squeals, and whistles. And if in the wild, to a neighboring group of gibbons, the call means, "Keep out!"