'Snooping' on dolphins offers acoustic clues to hotspots for food and friends

Dolphins perceive the ocean as a sound-based realm, employing whistles for communication and echolocation for navigation and prey detection. However, fish and human activities also generate noise in underwater environments. Researchers from Florida Atlantic University's Harbor Branch Oceanographic Institute have discovered new insights into dolphin behavior by listening to their acoustic interactions.

Equipped with an acoustic recorder, an autonomous wave glider recorded nearly 62 hours of underwater sound over two months, revealing distinct patterns in dolphin whistles and echolocation. Whistles, mainly linked to social behavior, were more frequently detected in nearshore waters and influenced by factors such as location, temperature, sound levels, and chlorophyll-a concentration.

Prominent areas of whistle activity were observed near St. Augustine, Ponce Inlet, Melbourne Beach, and north of Ponce Inlet. Echolocation, characterized by rapid-fire clicks, was concentrated between Melbourne and Ponce Inlet and offshore toward Long John Reef, coinciding with high densities of sound-producing fish. This suggests dolphins may be using acoustic cues from their prey while hunting, potentially pinpointing feeding grounds.

The study also highlights the complex relationship between dolphins and their prey, as well as the potential for acoustic eavesdropping. Future research could explore whether fish listen for dolphins and vice versa. Additionally, vessel noise can interfere with dolphin communication and hinder scientific detection. The findings underscore the significance of acoustic monitoring in identifying critical dolphin habitats and informing conservation efforts in human-impacted coastal waters.