The coquí llanero frog

is a yellowish, peanut-sized creature that lives only in a single Puerto Rican wetland. It has a squeaky call that lies near the upper range of human hearing—ko-kee, ko-kee, which gives it its name—and as it squeaks, its jowl inflates like a balloon.

The frog was discovered in 2005. By 2012, it was already designated an endangered species. For the past five years, biologists at the University of Puerto Rico looking to track and protect the frog have been taking advantage of its unique call to monitor its status by sound. Using solar-powered iPods installed out in the Puerto Rican wetland, the scientists recorded the soundscape for 1 minute of every 10, 24 hours a day, and uploaded the data to their website, called the Automated Remote Biodiversity Monitoring Network (ARBIMON). They then used computer models to analyze the data and pick out the frog's call.

It's an unusual way to track the health of species, but one that could help researchers track other creatures in the wild: The approach could be used to observe any species that makes detectable noise. Furthermore, the website is not just for University of Puerto Rico researchers. Their system, which they report on in a study in the journal PeerJ, is open to everyone.

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One Million Recordings

Chirp. Cheep. Buzz. Howl. Many animals reveal their presence by making noise, and recording the sounds of an environment creates an audio snapshot of many of the animals present. Recorders, like this team's solar-powered iPods, can gather data from many places at once—much more data than even the most tireless field biologist could. Yet without systems to analyze the recordings, all this data would overwhelm researchers. That's where ARBIMON comes in, says Gonçalo Ferraz, a biologist in Brazil whose lab uses the system to study the distributions of birds in the Amazon rainforest over time.

"Without ARBIMON, we would have to listen to thousands of hours of recordings in order to find where are the species that we want to locate," he says. Ferraz estimates that he has uploaded 5000 hours of recordings from 100 sites spread over nearly 200 square miles. "No one can sit through 5000 hours to look for a bird," says Ferraz. "With ARBIMON, we can have a computer do that searching for us very quickly."

Using a freely available application on the ARBIMON website, scientists can train the computer to recognize particular sounds from their data by uploading their recordings to the site and picking out several examples of the call for the computer to recognize. They can test the model on calls identified by human experts before moving on to the unknowns. "Once they get to a level where they feel confident that the model works well," says T. Mitchell Aide, a biologist at the University of Puerto Rico and lead author on the study, "they can run that model over hundreds of thousands of recordings in just a few hours."

ARBIMON also lets users share their data. Once a user has made a model to identify the call of a particular species, other users can then apply it to their data. "There are other software packages that can help you locate sounds in a recording. The new thing, and the really special thing about ARBIMON, is the ability to do that with a very large number of recordings at once and with many users," Ferraz says.

The site currently has 1.3 million 1-minute recordings. Over the past five years, researchers at the University of Puerto Rico have used the system to monitor the growth and decline of nine different species, including a poison dart frog, a howler monkey, a toucan, and the coquí llanero. In their paper, the researchers report that the accuracy of ARBIMON's models ranged from 79 to 99 percent. They found that the coquí llanero populations seemed to decline from 2008 to 2012 but then rebounded last year.

Soundscape Library

Bioacoustics research—using sound analysis to study biology—is growing in popularity. For example, at the Bioacoustics Research Program at the Cornell Lab of Ornithology, scientists record sounds from whales, birds, and even elephants to learn about their diversity and communication. In the case of right whales, recording devices in shipping lanes off the Massachusetts coast allow Cornell to warn ships, lest they hit the endangered marine mammals. Cornell has also developed open-source software for analyzing animal sounds.

For the ARBIMON team, it's about big data. It might not seem like a big deal to use these recordings to capture small fluctuations in the population of a frog, but the value of the data may change as time passes. Just as people see different things in a photograph, different scientists may reexamine old soundscapes and find different species. This is just the beginning of what Aide and colleagues hope will be a long-term record of biodiversity changes over time.

"We know that climate change and land-use change are changing the distribution and abundance of species, but we really don't have good long-term measurements to say how they're changing them," says Aide. "It would be really nice if we had 10 or 20 years of data that we could correlate with those changes in climate or deforestation to be able to show how the species are responding."

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