Short Wave: These Scientists Are Using AI To Listen To Frogs

Released on July 18, 2025, by NPR’s Short Wave, this episode delves into the innovative use of artificial intelligence (AI) in conservation efforts to revive the California red-legged frog, a federally threatened species.

Introduction

Hosted by Regina Barber, the episode introduces science correspondent Nate Rott, who brings attention to a unique conservation project involving frogs and AI technology.

Regina Barber [00:29]: “Hey, Nate.”

Nate Rott [00:29]: “Hey, Regina. I am overjoyed to be back, but mostly I am overjoyed to talk to you today about frogs and more specifically, an AI acoustic model to find them.”

The California Red-Legged Frog

The episode centers around the California red-legged frog, the largest native frog in the western United States, which can grow up to five inches. Historically widespread from the Sierra Nevada Mountains to the Baja Peninsula in Mexico, the species has seen a dramatic decline over the past 150 years, now occupying less than 70% of its original range.

Susan North, Director of Stewardship for the Nature Conservancy in California [01:34]: “The California red-legged frog is the largest native frog in the western United States, meaning it can grow up to a whopping five inches in size.”

Nate Rott [02:06]: “But it wasn't just the miners and their voracious mining appetites. Non Native American bullfrogs sharing the blame. They will also eat native frogs. Got it. And there's other things, too.”

The primary cause of this decline has been habitat loss, with wetlands being converted into agricultural lands, parking lots, and polluted ponds, creating a substantial 260-mile gap in the frog's habitat between North Los Angeles and Central Baja. This fragmentation prevents natural recolonization of frogs across these regions.

The Reintroduction Effort

In response to the decline, various groups, including the Nature Conservancy and federal agencies, initiated efforts to reintroduce the red-legged frog to Southern California. The project involves relocating frogs from Baja, Mexico, to restored habitats in San Diego and Riverside counties.

Regina Barber [05:03]: “So this story is actually kind of wild. And it starts down in Baja, California in Mexico.”

Annie Peralta Garcia, Fauna del Noroeste [05:08]: “My name is Annie Peralta Garcia. I work at Fauna del Noroeste, a non-profit in Ensenada.”

Annie Peralta Garcia, a biologist with a longstanding commitment to the red-legged frog, spearheaded the founding of Fauna del Noroeste to focus on research and habitat restoration. Genetic testing revealed that the remaining frogs in Southern California more closely resembled those in Baja, making the translocation from Mexico a viable conservation strategy.

Robert Fisher, U.S. Geological Survey [06:28]: “And thinking about, you know, reintroducing frogs and bringing them back and restoring these ecosystems, it became clear we needed to use a Mexican source for the frogs.”

In 2020, two sites in Southern California were approved for receiving relocated frogs. Despite logistical challenges posed by the COVID-19 pandemic, the relocation was successfully executed using helicopters to transport egg masses from Baja to the U.S. border and subsequently to the designated sites.

Challenges in Monitoring Frog Populations

Post-translocation, the critical question was whether these efforts were yielding positive results. Monitoring the success of the reintroduction required determining if the frogs were breeding and establishing stable populations. Traditional methods of manually listening for frog calls in thousands of hours of nighttime recordings were impractical due to the volume of data and background noise.

Susan North [07:56]: “A really important measure of success comes kind of at about 5 years of age. That's when they should start breeding. So the first Translocation was in 2020. We're now in 2025.”

AI Acoustic Models: A Solution

To address the monitoring challenges, scientists partnered with software engineers to develop custom machine learning models capable of identifying the specific calls of the California red-legged frog amidst a myriad of other sounds, including other frog species, wildlife, and anthropogenic noise.

Nate Rott [10:24]: “Bennett says it can sort through the data in like tens of minutes. So they even created another model, like another AI model to identify the calls of those non native bullfrogs so they can get ahead of any New threats.”

Bennett Hardy, San Diego Natural History Museum [10:47]: “I spent countless hours by myself in a kayak all night long listening for bullfrogs. It's not the most efficient use of time. What they've done with AI on this project and those audio moss is incredible. It's, it's systematic monitoring of two species.”

The implementation of AI drastically reduced the time required to process audio data, enabling researchers to efficiently identify the presence and breeding activities of the red-legged frogs.

Success and Future Plans

The collaboration bore fruit when, in the previous winter, the AI models successfully detected the distinct mating calls of the California red-legged frog in Southern California for the first time in 25 years. This breakthrough was confirmed by discovering new egg masses near the detection points, indicating successful breeding.

Nate Rott [11:57]: “Well, they were at least trying to breed. Right? That's what the sound suggests.”

Clark Winchell [12:10]: “We knew right then and there that hey, this whole thing is successful. It's working. All of our hard work over the last six years and beyond for this species in this region is starting to pay off.”

Moving forward, the team plans to continue translocating frogs to further areas within the significant habitat gap, with the ultimate goal of establishing self-sustaining populations that could potentially lead to the species being removed from the endangered list.

Importance of Conservation

The episode underscores the broader significance of conserving species like the California red-legged frog. Beyond their intrinsic value, these frogs play a crucial role in controlling mosquito populations and mitigating the spread of diseases such as Zika, dengue, and West Nile virus.

Bennett Hardy [13:43]: “He has a line. A good tinkerer keeps all the parts. And I will just say, in my day of rebuilding carburetors on old trucks, when you got them done and there's one screw laying on a table, you knew you were screwed. I don't think any scientist has an answer on that. But it is important to maintain biodiversity as best we can moving forward.”

This analogy highlights the interconnectedness of ecosystems, emphasizing that the loss of one species can have unforeseen and detrimental impacts on the entire environment.

Conclusion

Nate Rott and Regina Barber conclude the episode on a hopeful note, celebrating the successful integration of AI in conservation efforts and the promising future of the California red-legged frog.

Regina Barber [14:31]: “Wow. Okay, so they are mating, they are making babies.”

Nate Rott [14:22]: “And the hope is that when these populations become self-sustaining, they'll be able to start like translocating egg masses from these Southern California sites to new ones to keep seeding new populations in that big gap we talked about.”

The episode serves as an inspiring example of how technological innovation can aid in preserving endangered species and restoring ecological balance.

Produced by Hanich, created by showrunner Rebecca Ramirez, and fact-checked by Tyler Jones, this episode of Short Wave showcases the vital intersection of technology and environmental conservation.