A groundbreaking new study has revealed that rig sharks (Mustelus lenticulatus) may not be as silent as once believed. Researchers from the University of Auckland and the Woods Hole Oceanographic Institute recorded juvenile rig sharks producing loud clicking sounds by snapping their flat, interlocking teeth together. These clicks, which lasted only about 48 milliseconds, reached up to 156 decibels and spanned frequencies from 2.4 to 18.5 kilohertz &mdash some of which are audible to humans. The study, published in Royal Society Open Science, is the first documented evidence of intentional sound production in this shark species, challenging the long-held assumption that sharks are silent predators due to their lack of sound-producing organs.

The clicking behavior was most frequent when the sharks were being moved between tanks or gently handled, with the number of clicks dropping as the animals became accustomed to the experimental routine. About 70% of the clicks occurred while the shark swayed slowly side to side, while 25% happened during more explosive movements. The researchers believe the clicks likely result from the snapping of the rig shark's strong, platelike teeth, which are normally used to crush crustaceans. The regularity and intensity of the clicks suggest they may be intentional and possibly serve as distress signals or warning sounds, though their exact purpose remains unclear, especially since most clicks fall outside the species&rsquo hearing range.The discovery raises intriguing questions about shark communication and behavior.

The discovery raises intriguing questions about shark communication and behavior. With over 500 shark species in existence, researchers now wonder if others may also produce sounds previously undetected. The study has opened new avenues for exploring shark vocalizations in natural habitats, particularly how sound might play a role in signaling danger or deterring predators. Scientists hope to investigate whether rig sharks make similar noises in the wild, which could significantly enhance our understanding of their social interactions and ecological roles.