Free of offshore wind turbines, dolphins off Florida’s coast may be hunting by ear and 62 hours of underwater recordings show exactly where their clicks, whistles, and acoustic hotspots converge
An autonomous wave glider recently drifted through coastal waters off the Atlantic shoreline, its submerged microphones recording underwater sounds across open ocean ecosystems. Advanced acoustic monitoring allows researchers to evaluate marine environments without disturbing sensitive aquatic life.
Ocean waters along the southeastern United States host complex biological communities where sound plays a fundamental role in survival. For marine mammals, acoustic signals represent the primary tool for navigating, communicating, and locating prey in murky environments.
Understanding how marine species utilize soundscapes provides critical insight into coastal ecology. Recent technological advances have made continuous, long-term acoustic data collection far more comprehensive than traditional visual surface surveys.
The survey logged over 62 hours of continuous acoustic recordings, providing researchers with enough data to build detailed spatial maps of regional sound activity.
Two sounds, two purposes
Dolphins rely on two distinct types of acoustic emissions, each performing a specialized function in their daily survival.
Whistles serve primarily as social communication tools. These vocalizations keep traveling pods connected, signal food availability or danger, and help maintain individual identity across group members.
Each dolphin develops a unique signature whistle early in life, functioning much like an acoustic name. Mothers frequently repeat their signature whistle before and after giving birth, ensuring newborn calves quickly recognize them.
Echolocation clicks fulfill a completely different biological purpose. Instead of communicating with other animals, dolphins emit high-frequency acoustic pulses to map their physical surroundings.
These rapid pulses travel through the water column, strike physical targets, and bounce back as return echoes. By processing these returning signals, dolphins determine the exact size, shape, speed, and distance of surrounding objects.
The timing of these clicks adapts dynamically. Dolphins slow pulse rates when scanning distant targets to allow returning echoes sufficient travel time, while accelerating click rates when closing in on nearby prey.
62 hours of listening along the East Florida Shelf
To evaluate how marine mammals utilize these distinct sounds in natural habitats, marine scientists from Florida Atlantic University deployed an autonomous wave glider.
Equipped with specialized underwater acoustic recording devices, the autonomous vessel traversed the continental shelf, capturing vocalizations across varying water depths and sea conditions.
The survey logged over 62 hours of continuous acoustic recordings, providing researchers with enough data to build detailed spatial maps of regional sound activity.
By isolating social whistles from echolocation clicks, researchers mapped where each vocalization type concentrated across the study region.
Clear patterns emerged across coastal regions. Whistle concentrations appeared near St. Augustine, Ponce Inlet, and Melbourne Beach, indicating designated social zones where animals gathered primarily to interact rather than hunt.
Where the clicks led: A noisy overlap
Echolocation activity revealed a markedly different spatial distribution across the marine environment.
Click hotspots clustered around Melbourne Beach, Ponce Inlet, and Long John Reef. While these areas partially overlapped with social whistle zones, they displayed a distinct acoustic signature.
These locations stood out for another significant reason: they coincided directly with high vocal activity from sound-producing fish species.
While lacking vocal cords, certain fish species generate underwater sounds using specialized muscles or body structures to attract mates and warn off predators.
This spatial convergence suggests that dolphins do not rely solely on active sonar. Instead, they likely use passive acoustic listening, tuning into ambient fish sounds to identify rich feeding grounds before activating targeted echolocation.
Reading the ocean by sound: What this means for conservation
Acoustic habitat mapping provides an essential tool for ocean conservation efforts, enabling scientists to identify critical feeding and social zones even when animals remain unseen at the surface.
Longitudinal data also highlighted clear seasonal shifts. Acoustic detections peaked in March before declining in April, reflecting migratory patterns along the Atlantic coastline.
However, several key vocalization hotspots overlap heavily with commercial and recreational vessel lanes along the coast.
Engine noise can mask essential clicks and whistles, disrupting communication networks and interfering with foraging efficiency across critical habitats.
Identifying where human impacts intersect with vital wildlife habitats provides the baseline data necessary to establish targeted coastal management protections.
This brings us to the ultimate reveal: off Florida’s Atlantic coast, dolphins may be hunting by ear—and 62 hours of recordings reveal where their clicks and whistles converge.
Kelly is an experienced writer with 15 years of experience exploring the big stories that shape our world, from tech breakthroughs and space exploration to climate, energy, and the fascinating quirks of science. She has a talent for turning complex ideas into sharp, memorable insights that stay with readers long after they’ve finished reading.
