Clicking Sharks: Discovery of Vocalization in Houndshark Species
Scientists have discovered that at least one shark species, the houndshark (Mustelus lenticulatus), produces clicking sounds, challenging the long-held belief that sharks are silent creatures. This groundbreaking finding, reported by researchers, marks the first documented instance of vocalization within this group of marine animals, suggesting a potential new avenue in understanding shark communication and behavior in ocean environments. The research sheds light on shark sounds and opens possibilities for utilizing acoustic monitoring in shark conservation efforts.
Unexpected Shark Vocalizations
During her doctoral research focused on shark auditory capabilities at the University of Auckland in New Zealand, marine biologist Carolin Nieder, now affiliated with Woods Hole Oceanographic Institution, observed unusual sounds. While handling rig sharks (Mustelus lenticulatus) for experiments, Nieder noticed a distinct metallic clicking noise emanating from this specific houndshark species.
Initial Skepticism and Confirmation
“Initially, I dismissed it,” Nieder stated, “because sharks were presumed to be non-vocal. However, the clicking persisted.”
While intentional sound production is prevalent among terrestrial vertebrates, demonstrated by diverse bird songs and mammal calls, underwater acoustics in fish are often attributed to physical actions or muscle vibrations. Although some ray species, close relatives of sharks, were reported to click when disturbed in 2022, formal descriptions of shark sounds remained absent until this discovery.
To validate the rig shark’s sound production, Nieder and her team brought ten juvenile specimens, captured off the coast of New Zealand’s North Island, into a controlled laboratory setting. The sharks were placed in tanks equipped with highly sensitive sound recording devices. Through gentle handling, the research team confirmed that each shark emitted a clicking sound in response. This observation positions the rig shark as the first known shark species to generate sounds seemingly independent of other activities like feeding or accidental contact.
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Mechanism of Sound Production
Researchers hypothesize that the clicking sounds are produced by the sharks rapidly snapping their jaws. Similar to clicking rays, rig sharks possess flattened teeth, which could generate a sharp, percussive sound upon impact. An audio recording of the shark clicks is available for listening.
Potential Functions of Shark Clicks
Further investigation is planned to pinpoint the precise source of the clicks and determine their function. Nieder suggests that as a smaller shark species vulnerable to larger predators, the clicking might serve as a defense mechanism when threatened.
Defensive or Offensive Communication?
“The sound could potentially disorient a predator momentarily,” she speculated. Nieder also proposed the possibility that the clicks may play a role in hunting, potentially startling or confusing their crustacean prey.
Implications for Shark Biology and Conservation
Aaron Rice, a researcher at Cornell University, unrelated to this study, highlights the significance of this discovery for shark biology. He stated, “This is a potentially crucial, yet previously overlooked, area in understanding shark life.”
Acoustic Monitoring for Shark Populations
Rice suggests that if sound production is common among sharks, their clicks could become a valuable tool for monitoring their often-declining populations. Existing vast datasets of underwater sound recordings from fish and whale research might already contain undiscovered shark sounds. Analyzing this archived data could provide insights into shark presence in various regions, offering a supplemental method for tracking these vulnerable marine predators.
Newfound Discovery in Ocean Biology
“[This finding] truly represents a novel discovery in fundamental biology,” Rice concluded. “It underscores the vast extent of our knowledge gaps regarding the ocean realm and the diverse life it harbors.” This discovery encourages further research into shark communication and the broader role of acoustics in marine ecosystems.