Scientists Repurpose Seismic Monitors to Track Rare Whales with AI

In an innovative leap for marine conservation, scientists in south China's Guangxi Zhuang Autonomous Region have repurposed land-based seismic equipment to monitor the vocalizations of the endangered Bryde’s whale. By applying advanced deep-learning algorithms to data collected from an island-based seismometer, the research team has created a cost-effective, continuous monitoring system that captures whale calls far below the threshold of human hearing.

The study, led by Xiao Zhuo, an associate professor at Guangxi Minzu University, and published this week in the journal Geophysical Research Letters, details how the team trained an AI model on more than 1.7 million labeled seismic samples. The resulting system can isolate and classify whale vocalizations from environmental background noise with 99 percent accuracy.

Expanding Conservation Through Existing Infrastructure

Traditional marine acoustic research often relies on hydrophones—underwater microphones—which can be expensive to deploy and maintain. By contrast, seismic stations are already widely distributed in many regions, particularly on islands and near tectonic zones.

"What genuinely astonished us was that the low-frequency sound energy emitted by Bryde’s whales could travel kilometers to the island and still be received by the seismometer with such clarity," said Xiao. The system detected whale vocalizations as low as 5 Hz—frequencies significantly lower than those typically captured by standard hydrophones. These rhythmic pulses, recurring every five to 13 seconds, bear a striking resemblance to mating songs, providing new insights into the breeding behaviors of these elusive marine mammals.

Surprising Findings on Migration Patterns

The research has significantly altered the scientific understanding of Bryde's whale migration in the Beibu Gulf. Previous coastal visual surveys had suggested that these whales migrated out of the area by April each year. However, the seismic data revealed a different reality: whale calls were detected continuously from January through July in 2021, with activity peaking in February and March and persisting into midsummer.

This acoustic evidence has been bolstered by reports from local fishermen, who documented sightings of whales roughly 38 km southwest of Xieyang Island as late as July. Chen, a collaborator on the project who has conducted fieldwork in the region since 2018, noted that this discovery provides stronger empirical backing for understanding the population's seasonal presence.

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"Organizers stated that" the use of existing seismic networks provides a scalable solution for 24/7 marine mammal monitoring at a fraction of the cost of traditional equipment. According to officials, this approach offers a promising model for global conservation, particularly in regions where tectonic activity or island geography allows for the integration of earthquake monitoring and marine biological research.

Why It Matters

This technology bridges a gap in marine research by leveraging infrastructure already in place for geophysical monitoring. For conservationists, the ability to monitor endangered species continuously without the high costs of specialized underwater gear could prove transformative. By triangulating ground motion in three dimensions, the system also offers the potential to pinpoint the real-time location of vocalizing whales, assisting in efforts to reduce ship strikes and mitigate the impact of industrial vessel traffic on protected populations.

Key Facts at a Glance

• AI Accuracy: The deep-learning model identifies whale calls with 99 percent accuracy.

• Unique Detection: The system captures low-frequency sounds as low as 5 Hz, well below human hearing and most conventional hydrophone capabilities.

• Migration Insight: Data indicates Bryde’s whales remain in the region until at least July, challenging earlier beliefs that they migrated by April.

• Cost-Efficiency: Repurposing existing land-based seismometers offers a continuous, low-cost alternative to expensive underwater acoustic arrays.

FAQ

Can this system replace traditional hydrophones?

It complements them. While seismometers excel at detecting very low-frequency seismic vibrations, the two technologies can be used together to provide a more comprehensive acoustic profile of marine environments.

Is this technology applicable to other regions?

Yes. Researchers suggest that because seismic monitoring stations exist globally, particularly in island and tectonic regions, the AI model could be adapted to track other large baleen whale species worldwide.

What does the 5 Hz frequency imply?

Sounds at this frequency are consistent with the "songs" or mating calls of large baleen whales, suggesting that the studied area is a critical site for courtship and breeding behavior.

Source: Geophysical Research Letters, Xinhua News Agency