Overview

• Researchers analyzed more than 2,000 hours of recordings from a single red hind spawning aggregation off Puerto Rico that has been continuously monitored since 2007.
• Male red hinds produce two distinct low-frequency grunts tied to behavior, with one associated with courtship and another used for territorial defense.
• Courtship calls predominated from 2011 through 2017, then territorial calls rose beginning in 2018 and had nearly tripled by the end of the study period.
• Spawning activity remained seasonal and closely aligned with lunar cycles, and recent years showed more frequent or multi-day peaks in sound production.
• A custom classifier called FADAR processed 12 years of audio in weeks and the team notes possible causes for the behavioral shift as hypotheses rather than confirmed drivers.