It is 6 am and the sun is barely creeping up through the trees. A sound much like a siren sidles into my consciousness waking me in my tent. The sound grows louder and the frequencies increase as the minutes go by. After several minutes, cacophony erupts and branches begin to shake as if being disturbed by a forceful wind. I have just witnessed the morning song of a group of gibbons who live in the trees above me. Gibbons are socially monogamous, territorial, and live in small family groups with their offspring. Every morning at dawn the adult male and female sing a duet that is loud enough to let other gibbon groups know that they maintain their territory; much like a siren warns people to stay away from danger. Yet the song is perfectly configured and arranged, shaped by evolution, and thought to solidify the sometimes life-long social bonding between males and females. I am fully awake now. The song has finished and the gibbons seem to have disappeared instantly. My day has just begun.
Listen to a morning duet of a group of white-cheeked crested gibbons here.
http://youtu.be/bKvcIRgHa4U
Notice the individual singing alone at the beginning. That is the adult male. He will often sing for several minutes on his own. The female joins in with notes of increasing volume and frequency and then twitters out. The male follows her immediately with a coda that sounds like “wee uh wee uh weet” in my best imitation. If there are juveniles in the group they will sing along with the adult female when she sings. Both male and female juveniles sing the female song. It is only when they reach sexual maturity that males leave their family and begin to sing the male song on their own, probably to attract and secure a mate.
When I was working on my Master’s thesis researching gibbon song I listened to hundreds of recordings. Every time I would play one my cat would freak out and run in circles or jump on things. I have also played the recordings when I am lecturing on primates in biological anthropology (101) at PSU. It makes me smile to see the faces of the students and hear them say that they never expected it to sound like that!
Recently I have been hearing the songs of more groups from far away. Perhaps because it is the dry season the song is carrying better. I have heard gibbons sing many times in captivity but there is nothing like hearing their song in the wild! It has been so lovely to hear them and realize clearly that there are more groups nearby. They are saying “We are here. Don’t let us go!”