Archived Abstracts
Validation of an acoustic location system to monitor Bornean orangutan (Pongo pygmaeus wurmbii) long calls
Authors: Brigitte Spillmann, Maria A. van Noordwijk, Erik Willems, Tatang Mitra Setia, Urs Wipfli, Carel P. van Schaik
Individual Bornean orangutans usually travel alone through the forest, but that does not mean there are no social influences on their movements. One way to find out how animals influence each other’s movements is by examining the reactions to the long calls of the large fully-grown ‘flanged’ males, the ones with the massive cheek pads. Long calls can be heard at a distance of a km or more, when animals are out-of-view of each other. We can show that those who hear them adjust their range use, but obviously we do not capture the whole picture when we only follow single individuals and do so for limited periods of time. We therefore installed 20 time-synchronized, autonomous audio-recorders in a grid encompassing 3 km2 at Tuanan field station in Central Kalimantan (Borneo) to continuously record the sounds of the forest and in particular the long call of flanged males. With this microphone array in the forest we are then able to detect and localize all long calls emitted in the grid, and in a further step identify the calling individuals as they moved through it. In this paper, we tested this whole system, and demonstrated that it worked as intended. In future work, we can therefore examine the movements of these males relative to each other, and relative to other individuals relative to these males.
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