A lot of animals in a tropical forest make sound, by communicating with each other, trying to find mates, warn each other about predators. Considering all that sound together, as a “soundscape”, can tell us a lot about the state of the tropical forest. Even without identifying individual species according to their calls, we can say, for example, whether one soundscape is more saturated with sound than another. According to the acoustic niche hypothesis, animals have evolved to vocalize at different frequencies and times, so that they can communicate well. The idea is that if there are many species in a habitat, they have to compete for acoustic space, in other words, they have to vocalize differently to other species in order to be heard. How much of the acoustic space is taken up during a day, month, or even a year, can tell us how many vocalizing species there are.
Together with colleagues from The Nature Conservancy and the Queensland University of Technology, we are using these differences in soundscape saturation to develop a fast, cheap, and efficient biodiversity monitoring tool. To test this approach, we recorded the soundscapes, and analyzed their saturation, in different parts of tropical rainforest in the Adelbert Mountains of Papua New Guinea. Using Bioacoustic Recorders made by Frontiers Lab, we captured 35 different soundscapes, ranging from pristine forest, forests that are used for hunting by local people, and small patches of forest that have been converted to gardens or cocoa plantations.