use bioacoustics in wildlife conservation

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  • Audio recording devices can be used to answer questions about ecology and conservation, and to monitor landscapes through their soundscapes.
  • Elusive species can be discovered and studied more easily if soundscapes are constantly monitored.
  • Using recorders and performing fieldwork simultaneously can always give the best results.

On the Valparai Plateau in the Anamalai Hills, two researchers stand in a fragment of forest and listen intently. Both work on bioacoustics – studying sounds in a landscape (the soundscape) to learn more about the life around them.

One of them tries to discern whether the bird that gives a lively and cheerful call is a yellow-browed bulbul or an Asian blue-fairy bird. In the dense green vegetation around them, there is little hope of seeing the bird, so she has to rely on the call to identify the species.

Meanwhile, the other researcher has just completed his own task. He put a small audio recorder in a Ziploc bag and tied it to the trunk of a Cullenia tree bearing fruit in the form of a spiky ball.

The first researcher did a one-time bird count, where she just stood in one spot and took note of the species around her, mostly based on their vocalizations. The data thus collected is used to explore species diversity in forests and estimate bird abundance on a small scale. Studies like this depend on a high level of expertise, field effort and time. Often these surveys are done early in the morning and nocturnal birds and birds of prey are overlooked.

The second researcher, who has placed recorders in the field, will benefit from several advantages over the method of the first. Large areas of forest can be covered by placing multiple units simultaneously, and loggers can be programmed to collect data throughout the day, for weeks at a time. These data, free from individual bias, can be reanalyzed multiple times to answer a variety of questions. If programmed to capture sounds of the appropriate frequency, these recorders can capture the vocalizations of bats, frogs and insects in addition to bird calls.

Click to hear the cries of the birds. Audio recordings of a habitat can be used to identify species diversity, estimate small-scale bird abundance, and more. Graphic by Kartik Chandramouli.

VV Robin, assistant professor at the Indian Institute of Science Education and Research, Tirupati, uses bioacoustics to answer questions of ecology.

“The benefits of bioacoustics and the use of recorders are immense. One of the most popular uses of the technology is the implementation of camera traps to count tigers nationwide. However, one can imagine that the sound travels further (in most wooded landscapes), and one could potentially cover a larger area with acoustic recorders. The detection of rare species is an important application for which acoustic tools can be used. Another application of conservation is to understand the impacts of humans on biodiversity, ”he said.

Using loggers to detect elusive cash

Robin’s student, Chiti Arvind, is currently working on the detection of a critically endangered bird, the Jerdon’s Courser, at the Sri Lankamaleswara Wildlife Sanctuary in Andhra Pradesh. In these scrub forests, Arvind placed recorders and programmed them to record sounds from dusk to dawn, in an attempt to capture the call of the elusive nocturnal bird.

“We are now creating a model of the Jerdon’s Courser call from previous recordings collected by Dr P. Jeganathan (the only known record of this bird). This will then be used to filter the recordings retrieved from our acoustic recording units to find a similar vocalization match using available song analysis software, ”she explained.

A few years ago, trying to rediscover a bird like this would have required setting camera traps or laboriously searching for the bird’s footprints in the sand. “Although these methods initially aided in the detection of the Jerdon Courier, their success rate was not very high. Since this bird is nocturnal and cryptic, bioacoustics is a good technique to implement, given previous successful studies on similar birds. By using automated loggers, we can also monitor larger areas with the least human interference. Our goal is to create a detection framework for the long-term monitoring of this bird using bioacoustics, ”signed Arvind.

A passive recording device placed in a forest. Loggers can be programmed to collect data throughout the day, for weeks at a time. Photo by Vijay Ramesh.

Landscape monitoring through soundscapes

Besides searching for enigmatic species, bioacoustic monitoring in forests can also inform conservation. Researchers often think of recordings as “soundscapes” – the collection of all sounds in a given landscape.

The installation of loggers in poorly studied tropical forests can provide the first basic information about biodiversity in the interior. A saturated soundscape is considered a sign of a healthy ecosystem, and sudden changes can indicate human disturbance from logging and hunting.

Climate change can lead to more gradual changes. Around the world, researchers have documented phenological changes due to global warming, where birds and frogs call mates earlier in the season. Forest bioacoustic monitoring can help link rising temperatures to changes in animal behavioral ecology.

In disturbed forests, invasive species that have invaded the landscape sometimes mask the vocalizations of endemics, and recordings from these forests may offer the first indication of such takeovers.

Analyzing an area’s soundscapes over time allows researchers to learn more about biodiversity and habitat health.


Read more: [Commentary]: What sounds can reveal, if we listen


Combine bioacoustics and fieldwork

While loggers offer definite advantages over fieldwork, the data collected from loggers can quickly accumulate, making storage and management a nightmare. In addition, experts must provide training data before algorithms can be used to recognize and match patterns. Unless a renewable energy source can power the loggers, studies that rely on continuous monitoring will burn a staggering number of batteries.

Viral Joshi, another student in Robin’s lab, has been an avid bird watcher for most of his life. In recent years he has also taken to bioacoustic analysis. He believes that the best approach is still one that combines field surveys and recording devices.

“I am now using my knowledge of bird calls to understand complex behaviors using advanced analysis techniques and tools,” he said.

Soundscapes, like landscapes, are indicative of regional diversity and can be considered an important regional marker. These often change along a gradient of human activity, with anthropogenic noise replacing natural sounds in towns and villages. There is a strong case for preserving natural soundscapes – preserving them is about preserving the diversity of our wild places.

Robin is optimistic about the future of bioacoustics in India. “I think there is a lot of potential in this area. It is at the interface of ecology, physics, neurobiology and behavior. Its applications can be very broad and can even be used in critical aspects such as urban planning and informing policies.

QUOTE:

Burivalova, Z., Game, ET, & Butler, RA (2019). The sound of a rainforest. Sciences, 363 (6422), 28-29.

Burivalova, Z., Towsey, M., Boucher, T., Truskinger, A., Apelis, C., Roe, P., & Game, ET (2018). Using soundscapes to detect varying degrees of human influence over the tropical forests of Papua New Guinea. Conservation Biology, 32 (1), 205-215.

Pijanowski, BC, Farina, A., Gage, SH, Dumyahn, SL & Krause, BL (2011). What is the ecology of the soundscape? An introduction and overview of a new emerging science. Landscape Ecology, 26 (9), 1213-1232.

Banner image: Asian blue fairy. Photo by Rahul Alvares / Flickr.


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