When Nature Speaks to Those Who Listen: The Potential of Acoustic Monitoring at Bosque Pehuén

At Bosque Pehuén, autonomous recorders capture daily what the eye cannot reach or climate makes difficult to observe otherwise: songs of birds and amphibians shape the acoustic fingerprint of the forest and its landscape. A recent discovery of a tree frog (Hylorina sylvatica) never before recorded in the reserve reveals the potential of acoustic monitoring, which today unfolds across three lines of research (science, conservation, and art) to listen, transdisciplinarily, to the sonic language of wildlife.

Acoustic monitoring yields large amounts of data about biodiversity at a specific place and time, and is a method that attracts the interest of various disciplines. A soundscape (1) can be, at once, material for artistic creation and scientific research: two forms of knowledge that at Bosque Pehuén coexist and interweave to account for wildlife.

Acoustic monitoring distinguishes between two approaches: active (direct field observation, bird point counts) and passive (autonomous recorders that register without constant human presence). The latter is especially valuable in territories like Bosque Pehuén, where bad weather and low winter temperatures make foot-based monitoring difficult. Tomás Altamirano, FMA’s director of conservation, highlights that these devices have been key to “observing” hard-to-access ecosystems, allowing information to be gathered even when climatic conditions are extreme.

The resulting volume of data is unmanageable manually, so analysis begins with software that identifies vocalizations in spectrograms (2), a process complemented by researchers’ experience and collaborative platforms like Xeno-canto. Artificial intelligence allows, through transfer learning, adapting global models for detecting local species, although it always requires human intervention to validate results (3).

Our foundation’s natural reserve has become a living laboratory where researchers and artists come to experiment with convergences from their own projects. Through recorders—whether autonomous or those accompanying a traditional human sampling exercise—it has been possible, for example, to capture species that are not easy to observe visually or meteorological phenomena in their audible dimension, such as the puelche wind.

In June 2025, an autonomous recorder at Bosque Pehuén registered the song of an amphibian never before detected in the reserve: the tree frog (Hylorina sylvatica), which emerges at night or dusk to sing. During the day it remains hidden, making it very difficult to notice. Its presence was not documented by a field sighting, but by the croak captured in the recording.

Through acoustic recording, biophonies (birds, amphibians, insects, among others), geophonies (wind, rivers, rain, among others), and anthropogenies (human sounds and/or their artifacts) are captured. This multiplicity offers a more integral reading of the ecosystem: even the latter prove valuable, allowing for indirect detection of threats such as motorized vehicles or gunshots, information that guides more precise strategies for territorial care.

Acoustic Monitoring

Acoustic monitoring at Bosque Pehuén occurs through parallel approaches and projects. At Bosque Pehuén there are 12 recorders installed with the aim of complementing the interannual wildlife monitoring in our Natural Reserve. A second acoustic approach is volcano biodiversity monitoring, where we have 12 active recorders between November and March in the high areas of the Tolhuaca, Lonquimay, Sierra Nevada, Llaima, Sollipulli, Rukapillán, Quetruipillán, Lanín, Mocho, and Choshuenco volcanoes. This is part of the project FONDECYT Regular 2026 Mountain Bird Networks: interactions across elevation gradients and climate change in the temperate Andes, led by Tomás Altamirano. The research studies how nesting and flock networks of birds organize themselves across 10 volcanoes in La Araucanía and Los Ríos, using acoustic recording as a methodological tool.

We also have a collaboration with Soundlapse (4), a project by acoustic engineer and composer Felipe Otondo, associate professor at the Austral University of Chile. In October 2024, Felipe visited Bosque Pehuén to record bird sounds and the first pilot recorder was installed. The recording period began in September 2025 and will extend until September 2026, thus completing a full year of uninterrupted sampling with three recording units. Gabriel Morales, sound engineer, musician, and researcher in bioacoustics, is part of this team and both work researching acoustic communities of four southern ecosystems, including Bosque Pehuén.

Gabriel’s trajectory in acoustic detection is not new: during his master’s thesis he detected, through its song, the presence of Porzana spiloptera in urban wetlands of Valdivia—a species previously not recorded so far south—a finding that resulted in a scientific publication with the team of the Bird Ecology Laboratory at Austral University. His prior experience as a sound engineer for music, film, and documentaries sparked his interest in the geographic precision of bird songs.

The tree frog was first heard by Morales, sound engineer, musician, and researcher of the Soundlapse project, during an exploratory field review done alongside acoustic engineer and visual artist Felipe Otondo, when removing the memory card from one of the first recorders installed in the reserve. Gabriel shared the discovery with FMA’s conservation team.

Its detection constitutes the first glimpse of the species at Bosque Pehuén, something that gains relevance if one considers that a fauna inventory conducted in 2022 had documented only seven amphibian species without the tree frog among them. This occurs because the vast majority of amphibian and bird species that inhabit a forest are easier to hear than to see, says Tomás.

Diverse Species Recorded

Acoustic monitoring has allowed us to hear at Bosque Pehuén a diverse list of birds, for example: thrush, rayadito, fiofío, hummingbird, Patagonian cometocino, goldfinch, small woodpecker, and great tit, as well as the nighttime song of the barn owl. The material pending analysis raises expectations: “There are more findings that I believe will occur when we deeply analyze the data we are collecting from Bosque Pehuén because we are in the recording stage. We haven’t analyzed yet,” says Gabriel. Sebastián Carrasco, biologist and coordinator of conservation projects at FMA, poses questions that transcend inventory: “Acoustic monitoring could serve to deeply study interspecific interactions from the behavior of acoustic communities: how a woodpecker sings and communicates with a hued-hued, or if there is any information transfer between species.” These questions open horizons for future research.

Beyond Science

Work around sound at Bosque Pehuén transcends scientific approaches. Composer Fernando Matus de la Parra, for example, observed in 2021 that the songs of the forest’s main birds are distributed across different sonic registers, avoiding interference with each other. This natural acoustic balance explains the richness of sound in the place. Musician Gregorio Fontén, on the other hand, sonified in 2022 structural data of araucarias to generate Dendrophony, a score that translates biological information into harmonic possibilities and critiques the visuocentric paradigm of knowledge.

The Laboratory for Research in Atmospheric Sonorities (LISA), composed of Mauricio Lacrampette, Nicolás Alvarado, and Sebastián de Andraca, is another example illustrating the potential of acoustic monitoring where the boundaries between art and science can blur. It was born during one of the Bosque Pehuén residency cycles exploring the puelche phenomenon. As part of the residency explorations, Los árboles nos dejan oír el bosque (The Trees Let Us Hear the Forest) by Nicolás Alvarado also emerged, which seeks to access the forest’s interoception (5), how it internally perceives its own functioning. The work was launched under the Paisaje del Pacífico Label and presented at Docente Activo 2026 as an instance of acoustic immersion.

Likewise, aligned with the surge of sound art and its connection nodes with multiple disciplines, in November of this year, the team from Tsonami will visit Bosque Pehuén, an organization and cultural center based in Valparaíso dedicated to the promotion, development, and fostering of sonic practices and experimental art.

Footnotes

(1) Soundscape: A term coined by R. Murray Schafer to refer to the total acoustic environment, the complete sound field of a place, wherever we happen to be. Schafer defends the value of silence and sound itself as a source of creativity.

(2) A spectrogram is a visual representation of sound frequencies over time, which allows identification of acoustic patterns from different species.

(3) Recorders are programmed to capture one hour at dawn, one at dusk, and five minutes each hour during the day. Ambiguous sounds are provisionally labeled to continue analysis later, in an iterative process where researchers’ experience complements automatic detection.

(4) Soundlapse is the informal name for a succession of FONDECYT projects—the current one is already the third, in effect until 2029—focused on soundscape and artificial intelligence for bird detection.

(5) Interoception refers to the internal perception of states and processes of one’s own organism; applied to the forest as a living entity, it alludes to how the ecosystem “perceives” and self-regulates its functioning through its internal networks of biological and acoustic communication.