This recording was obtained while on expedition for Finding Bigfoot. An excerpt from my field notes is below (read my full report by clicking this link):
One night on the trip, we had some very intriguing action. We were doing calls from camp (wandering in the jungle at night would be a very dangerous thing to do in a tiger preserve) and we received call backs from the northeast. It sounded very much like the short “whooo” howl I was doing. The recorder was running, but the foreground noise really got in the way of much being heard on this recording. Still, two or three short vocalizations can be heard in the background of the recording. Only a short while after that, something pushed over a tree from that same area. Could this have been an orang pendek? I think it’s possible. Both of these behaviors have been reported before from the orang pendek and other apes. If this recording is of an orang pendek, then it is the only one in existence to my knowledge.
The recording isn’t very clear, but there are two or three mid-to-high pitch “woo” sounds behind the white noise. Compare these to sounds made by gibbons recorded in the same area:
While it is possible that the sounds were made by gibbons, they did not sound the same in person to me. The possible orang pendek vocalization was longer in duration. There was also a difference in timbre as well. Also, shortly after hearing this vocalization, something pushed down a tree in the same general area where the sounds came from. I do not know for sure that what made the sound also pushed down the tree, but the proximity of the two noises at least suggests this.