Post provided by Diego Llusia (he/him), Camille Desjonquères (she/her) and Sara Víllen-Peréz (she/her)

Many species produce sound as a means of communication, emitting calls or songs to broadcast information to others in the surrounding area. In this blog post, Diego Llusia, Camille Desjonquères, and Sara Víllen-Peréz discuss their research on recording animal calls and how these soundtracks can be used to help monitor the impacts of climate change. 

Soundtrack of global climate change

During spring nights, you might hear loud choruses performed by various frog and toad species near streams, ponds, or lakes. In these choruses, males use their songs to attract and orient towards potential mates in the dark. Similar communication exchanges occur among birds, insects and even humans.

The Iberian treefrog (Hyla molleri) uses its song to encounter a mate (author: Íñigo Martínez-Solano).

Aside from sexual signals, animals employ sounds for many other functions. For example, suricates emit alarm sounds to warn their social group of the presence of a predator. Numerous bird species use songs to defend territory or to maintain group cohesion during displacement, while their chicks use vocalizations to beg for food.

Living beings are also sensitive to climatic conditions, with most organisms requiring specific levels of rain, humidity, or temperature to reproduce and survive. For instance, many animals such as frogs restrict their reproductive activity to periods and localities that are favorable to them.

You may then wonder if the accelerated climate change our planet is experiencing could alter its natural soundtrack. Is climate change modifying the times and locations at which animals reproduce? Could acoustic communication and their important functions be compromised by new climatic conditions?

In our recent research, we apply new technologies to help answer these questions.

Eavesdropping on nature

Emerging technologies increase our capacity to detect changes in nature. Nowadays, we can employ sensor networks that work autonomously to measure all types of parameters, multiplying the number of ‘eyes’ and ‘ears’ that register natural phenomena and collect more data.

This new toolbox for biologists also includes acoustic sensors, small digital recorders that are able to automatically record sounds emitted by animals. These sensors allow us to monitor the activity of animals over large periods of time and in multiple places simultaneously. The use of this novel methodology, named passive acoustic monitoring, has significantly increased in recent years.

Installed in reproduction or migration zones, acoustic sensors can be programmed to record ambient sounds for thousands of hours. But the challenge is then to analyze the enormous volume of recordings. To achieve this, we use complex algorithms, similar to voice recognition software that are used on our phones.

Taking advantage of the characteristics of each sound, these algorithms are able to identify the specific species that are emitting the sounds. This way, acoustic sensors help us to detect species present in each area, their reproduction period, or the environmental conditions in which they are active.

Bioacoustics and biogeography

Scientific advances often come from the integration of distinct disciplines, each bringing complementary tools and knowledge to create new ideas and methodologies.

In our recent study, we propose a new method to analyze the impact of climate change in species that use sound to communicate. We combined different techniques of acoustic monitoring with tools from biogeography. In short, this new framework allows us to take advantage of the large amount of information collected by acoustic sensors to generate biogeographical models.

With this method, we manage to predict where and when changing environmental conditions will be appropriate for each species to sing over the next few decades. That is, where and when they will be able to reproduce and carry out activities that are essential for their life cycle. It also allows to forecast whether conditions are getting better or worse for these behaviours in each location over time.

This is a powerful predictive tool that helps to forecast the responses of species to changes in temperature and precipitation that are happening in their habitats. Some of the possible responses include the disappearance of certain populations in areas with adverse conditions (local extinctions) or the colonization of new areas with suitable conditions (local expansion). The method can also detect temporal advancements or delays of the reproductive schedule of species (phenological changes). These may breakdown the interactions between species within ecosystems, so future investigations should explore the potential consequences of these changes.

The Iberian treefrog

Our new study offers a step-by-step guide to apply this method, named acoustic Species Distribution Models (aSDMs). To test its efficiency, we use an acoustic monitoring dataset for the Iberian treefrog (Hyla molleri), a small anuran that employs sounds to find mates.

Results reveal that our new method is robust, as it can successfully predict the activity of treefrogs in current conditions. Our discoveries thus support the use of these models as efficient tools to evaluate the effect of climate change in this taxonomic group.

Forecasted spatio-temporal shifts in suitability for calling behaviour of Iberian tree frog between current climate and climates in 2061 and 2080, as predicted by acoustic species distribution models (aSDMs) under the RCP 8.5 climate change scenario.

Finally, we propose the integrated use of bioacoustics and biogeography to explore the capacity of sound-producing species to adapt to climate change. With this new tool, we show how emerging technologies offer opportunities to face this challenge.

You can read the full Methods in Ecology and Evolution article by following the link below:

Acoustic species distribution models (aSDMs): A framework to forecast shifts in calling behaviour under climate change.