Sharks have a keen sense of hearing, a capability often overshadowed by their strong sense of smell or acute electroreception. This sense is crucial in their marine environment. Unlike human hearing, adapted for air, a shark’s hearing is finely tuned for water, where sound travels faster and farther. This allows them to perceive disturbances and signals, helping them navigate and interact with their surroundings.
Shark Hearing Organs
Sharks detect sounds using an internal auditory system, lacking external ears. Two small openings behind their eyes lead to the inner ear. This inner ear contains three fluid-filled semicircular canals, primarily for balance, and several chambers: the sacculus, lagena, utriculus, and macula neglecta. These chambers house sensory hair cells, some topped with dense otoliths. Sound vibrations cause the denser otoliths and gelatinous structures to move, bending the hair cells and sending signals to the brain.
The lateral line system complements the inner ear. This network of fluid-filled canals runs along the shark’s body and head, connected to the exterior by tiny pores. Within these canals are sensory cells called neuromasts, with hair-like projections. Water movements, turbulence, or pressure changes displace these hair cells, triggering nerve impulses. While the inner ear processes sound, the lateral line system detects low-frequency vibrations and pressure changes, working with the inner ear for a comprehensive acoustic and mechanosensory perception of their surroundings.
Sounds and Distances
Sharks are sensitive to low-frequency sounds. Their hearing range typically spans from about 10 Hz to 800 Hz, with peak sensitivity often observed at frequencies below 100 Hz. Some research indicates they are most responsive to sounds lower than 375 Hz, and specifically attracted to frequencies between 20 to 60 Hz. In contrast, human hearing generally ranges from 25 Hz to 16,000 Hz, meaning sharks detect much lower sounds than humans.
Sharks are attracted to irregular, pulsed sounds, mimicking struggling or injured prey. These include the erratic thumping of a distressed fish, splashing, or certain boat engines. Such sounds act as an auditory beacon, signaling a potentially easy meal. Sound travels efficiently through water, allowing sharks to detect these signals from significant distances. They can perceive sounds from hundreds of meters away, with some studies suggesting detection from over a mile, depending on the sound’s intensity and frequency.
How Hearing Aids Survival
Hearing is a primary sense for sharks, often initiating their predatory sequence by alerting them to distant activities. This auditory capability enables them to locate prey, particularly in conditions where visibility is limited, such as murky waters or at night. They detect low-frequency sounds from struggling or swimming organisms, pinpointing potential meals from afar. This auditory cue often provides the first indication of prey, well before the target is within visual or olfactory range.
The lateral line system, working with the inner ear, also aids in navigation and environmental awareness. It helps sharks detect water currents, identify obstacles, and maintain orientation in aquatic environments. This allows them to create a “pressure map” of their surroundings, even in low visibility.
Sharks also use hearing to avoid larger threats. They may detect dominant predators or respond to deterrent sounds, like those mimicking orca calls, exhibiting avoidance behavior. Hearing may also play a role in navigation and some social interactions, such as schooling behavior.