How AI trained on birds is surfacing underwater mysteries

Perch 2.0, Google DeepMind’s bioacoustics foundation model, was trained mainly on birds and terrestrial animals yet performs strongly on underwater audio. The study shows that its learned audio embeddings can support accurate whale, dolphin, reef-sound, and killer-whale classification with only a few labeled examples. This suggests that large, broadly trained bioacoustics models can transfer across environments and accelerate marine research without requiring extensive underwater training data.

Underwater Mysteries and Bioacoustics

• Ocean recordings reveal animal behavior, species distributions, and unexplained sounds.
• The “biotwang,” recently attributed by NOAA to Bryde’s whales, illustrates how new calls and species identifications continue to emerge.
• Google has previously developed models for humpback whales and multi-species whale detection.
• Perch 2.0 extends this work despite having no underwater audio in its training data.

Transfer Learning for Custom Classifiers

• Researchers can use an existing model directly when its labels match their data.
• For new sounds or datasets, transfer learning avoids training a deep neural network from scratch.
• Perch 2.0 converts audio windows into compact numerical embeddings.
• A logistic regression classifier is then trained on those embeddings using labeled examples.
• This requires far less computation, experimentation, and training data than full neural-network training.

Evaluation on Marine Datasets

• The researchers tested Perch 2.0 with few-shot linear probes using 4, 8, 16, or 32 examples per class.
• Performance was measured using ROC-AUC, where values closer to 1 indicate better class separation.
• Evaluation datasets included:
  • NOAA PIPAN: Baleen-whale recordings, including minke, humpback, sei, blue, fin, and Bryde’s whales.
  • ReefSet: Reef biological sounds, fish, dolphins, anthropogenic noise, and waves.
  • DCLDE: Killer whales, humpbacks, abiotic sounds, unknown sounds, and killer-whale ecotypes.
• More examples generally improved results.
• ReefSet performance was already high with four examples per class for most models.
• Perch 2.0 was consistently among the best-performing models across datasets and sample sizes.

Comparisons with Other Models

• Perch 2.0 was compared with Perch 1.0, SurfPerch, and Google’s multi-species whale model.
• It also outperformed AVES-bird and AVES-bio on most underwater tasks.
• The results show that strong underwater transfer is not limited to models trained on marine audio.

Why Bird-Based Training Transfers to Whales

• The authors suggest that large models trained on extensive datasets can generalize effectively to unfamiliar downstream tasks.
• Shared acoustic patterns across animal vocalizations may allow representations learned from birds and other terrestrial species to remain useful underwater.
• The findings challenge the assumption that a model must be trained directly on underwater recordings to perform well on marine classification tasks.

Practical Tools for Researchers

• Google provides a paper and a Google Colab tutorial.
• The tutorial demonstrates an end-to-end workflow for building a whale-vocalization classifier.
• It uses NOAA’s NCEI Passive Acoustic Data Archive and Google Cloud.
• Researchers can create agile, task-specific models with relatively small labeled datasets.

Perch 2.0 demonstrates that broad bioacoustic pretraining can substantially reduce the effort required to study marine sounds. Researchers can begin with general-purpose embeddings and adapt them to new whale species, calls, or underwater sound categories using only modest labeled data.