Contrary to popular belief, some sharks may not be completely silent. A study reveals unprecedented behavior in a New Zealand species, challenging our understanding of these marine predators.
Elasmobranchs (sharks and rays) were previously considered incapable of producing voluntary sounds. This belief has just been shaken by surprising laboratory observations.
Mustelus lenticulatus was recorded emitting deliberate clicking sounds.
Image Paul Caiger An accidental discovery
The team at Leigh Marine Laboratory noticed that juvenile "Rig Sharks" produced snapping sounds during handling. These brief sounds (48 milliseconds) reached up to 166 decibels, equivalent to a firecracker.
Recordings showed that 100% of tested individuals produced these clicks, particularly during the first few seconds of handling. The frequency then decreased, suggesting a stress response rather than intentional communication.
According to the study published in
Royal Society Open Science, these sounds may come from the snapping of flat teeth, characteristic of this species. Unlike typical sharks, this species has molars adapted for crushing crustaceans.
A still mysterious function
Researchers dismiss the hypothesis of a distress call, as the click frequency exceeds sharks' hearing capacity. Instead, they might serve to temporarily startle a predator, as some rays do.
The absence of specialized sound-producing structures in elasmobranchs makes this discovery particularly intriguing. Scientists emphasize that the exact mechanism remains to be confirmed by further studies.
a) Dorsal view of a juvenile male Mustelus lenticulatus skull showing cartilaginous and dental structures.
b) Rostral view indicating the position of the chondrocranium, jaws, and dental system.
c) Ventral view showing upper and lower jaw cartilages.
d) Lateral view including the chondrocranium and associated elements.
e–f) Photos of the upper jaw showing flat teeth with rounded crowns and two small lateral cusps (f, black tips). A protrusion is visible on the lingual surface (f, black arrow), with short ridges at the crown base (f, h, white arrow).
g–h) Photos of the lower jaw displaying the same dental morphology.
This observation opens new avenues into the little-known behaviors of sharks. The authors hope other species will be similarly studied in their natural habitat.
Going further: how do fish produce sounds?
Sound production in fish relies on various anatomical mechanisms. About 1,000 species can emit sounds, mainly for reproduction, territorial defense, or predator alerts.
The swim bladder, a buoyancy organ, acts as a resonance chamber in many species. By contracting it via specialized muscles, fish generate audible vibrations, as seen in meagre or drum fish. Some also rub their pharyngeal bones or fins to create stridulations.
Elasmobranchs (sharks, rays) were considered silent due to lacking dedicated organs. Recent discoveries about Rig Shark tooth snapping show other mechanisms exist. Rays, for example, may produce clicks by violently jerking their heads upward.
Studying these sounds remains challenging in the wild. Hydrophones and underwater cameras are gradually decoding these behaviors, revealing unexpected acoustic communication in marine species.
Article author: Cédric DEPOND