When a bat ray named Luna bolted through her tank at the Hatfield Marine Science Center in Newport, Oregon, she wasn’t just fleeing a shadowy shape that looked like a predator—she was sending a silent alarm through the water, triggering panic in two other rays she couldn’t see or hear. That moment, captured on camera by Oregon State University researcher Joshua Bowman, marks the first documented evidence that cartilaginous fish—sharks, rays, and skates—use chemical cues to warn each other of danger, a survival strategy long known in bony fish but never before observed in this ancient lineage. The discovery, published in the Journal of Experimental Zoology Part A, opens a new window into the hidden communication networks of some of the ocean’s most misunderstood creatures.
For decades, scientists have known that when bony fish like minnows are injured or frightened, they release chemicals into the water that prompt others to flee. But whether sharks and rays—whose bodies are made of cartilage, not bone—shared this ability remained a mystery. Bowman, then a master’s student at OSU’s Big Fish Lab, designed an elegant experiment using three isolated tanks: one for the “signaler” ray and two for receivers, all separated by sight and sound. When he simulated a predator attack by gently chasing the signaler ray, the two downstream rays reacted within seconds—swimming faster, darting erratically, and avoiding the tank floor—despite having no visual or auditory clues. The only possible signal? A chemical disturbance cue carried in the water.
The bat rays used in the study were borrowed from the Oregon Coast Aquarium, making the research both logistically feasible and ethically grounded. At just a few feet wide, bat rays are far more manageable than their larger cousins, like white sharks, which can grow over 20 feet long. Yet they share a close evolutionary bond. “Rays are closely related to sharks, so studying their communication pathways can provide insights into sharks as well,” said co-author Taylor Chapple, associate professor and co-director of the Big Fish Lab. The findings may help explain why white sharks have been observed fleeing areas when orcas appear—even when no shark has directly seen the threat.
While the exact chemical compound remains unidentified, the behavioral response is unmistakable. This kind of silent alarm system likely evolved to increase survival in the wild, where early warnings can mean the difference between life and death. But the discovery also carries a sobering message for humans: disturbing one animal may unknowingly stress many others. “If they disturb these animals, in the wild or in controlled settings, they may be impacting more animals than just the one in front of them,” Bowman said. As researchers continue to decode the secret signals of the sea, this study reminds us that even in silence, the ocean is always speaking.