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Unmasking the Ocean’s Chorus: Scientists Record First Shark Sounds
For years, the depths of the ocean have echoed with the calls of dolphins, the songs of whales, and the diverse vocalizations of fish – from croaks to chirps, grunts, hums, and growls. However, one group of marine predators has long been considered silent inhabitants of this aquatic soundscape: sharks. Breaking this long-held assumption, researchers have recently documented the first instance of a shark actively producing sound, adding a new dimension to our understanding of underwater acoustics and shark communication.
Rig Sharks Break the Silence
A study conducted by scientists at the University of Auckland in New Zealand has revealed that rig sharks (Mustelus lenticulatus) are capable of generating distinct clicking sounds. These shark sounds, resembling sharp snaps, were recorded by researchers and are believed to be produced by the shark snapping its teeth. This groundbreaking discovery, published in the journal Royal Society Open Science, marks the first documented evidence of active sound production in sharks, challenging their reputation as silent hunters.
Unexpected Discovery During Hearing Research
The lead researcher, Carolin Nieder, stumbled upon this intriguing shark vocalization while investigating the auditory capabilities of these creatures. During the handling of a rig shark, she was surprised to hear a clear clicking, snapping sound, which she described as akin to an electrical spark. This initial observation prompted further investigation into the sound-producing mechanisms of sharks.
About the Rig Shark
The sound originated from a rig shark, a relatively small species prevalent in New Zealand waters. These sharks typically reach lengths of up to five feet and primarily feed on crustaceans. Interestingly, rig sharks are preyed upon by larger shark species and are also commercially fished in New Zealand for use in popular dishes like fish and chips.
Investigating Shark Sounds in Captivity
Intrigued by the initial auditory encounter, Dr. Nieder and her team conducted a formal study. They observed ten rig sharks kept in tanks equipped with underwater microphones to monitor their behavior and any potential sound production. The researchers noted a consistent pattern: all ten sharks emitted the clicking noise when they were transferred between tanks or gently restrained.
Mechanisms Behind Shark Vocalizations
Unlike many fish that utilize a swim bladder – a gas-filled sac acting as a resonating chamber – for sound generation, sharks were previously thought to lack such mechanisms and were presumed to be incapable of actively creating sounds. This new research challenges this view, suggesting that teeth-snapping may be a mode of shark communication, albeit perhaps not in the way initially conceived.
Clicking Behavior Under Stress
Analysis of the recordings revealed that the sharks clicked approximately nine times within a 20-second period. Importantly, the shark clicking sounds were not observed during feeding or swimming activities. This led the scientists to hypothesize that the sounds are more likely associated with stress or startlement, rather than serving as a deliberate form of communication among themselves.
Defense Mechanism and Future Research
Dr. Nieder suggests that these shark noises may function as a defensive mechanism, particularly when the sharks feel threatened. She noted that many fish species snap their teeth or jaws as a way to deter or confuse potential predators. Further research is needed to determine if sharks can perceive these clicks themselves, whether this behavior occurs in their natural habitat, and if the sound is a deliberate action or an involuntary response to being startled.
Broader Implications for Marine Acoustics
Christine Erbe, director of the Center for Marine Science and Technology at Curtin University in Australia, commented that this study contributes to the expanding field of research on marine animal sounds and auditory perception. She emphasized that as scientists actively investigate, they are discovering an increasing number of species that utilize sound in various ways.
Rethinking Marine Communication
While acknowledging that the discovery of shark sounds is not entirely unexpected in light of growing research, Dr. Erbe highlighted its significance. She stated, “I think it’s significant in the sense that we totally underestimate the communication between animals and their environmental sensing abilities, and therefore also how we can impact them with noise.” This research underscores the complexity of marine communication and the potential impact of human-generated noise pollution on ocean life.