Clams, common inhabitants of marine environments, are often perceived as quiet, stationary organisms. These bivalves, encased in their protective shells, do produce sounds. While not creating melodies or complex calls, clams generate various noises from their daily activities. Understanding these sounds offers a glimpse into their hidden world beneath the water and sediment.
How Clams Create Sounds
Clams produce sounds primarily through mechanical actions, often as a byproduct of their movements. One common way is the clicking or clacking of their shells. This occurs when clams burrow into sand or mud, involving muscular contractions and shell adjustments to move through the substrate. For instance, razor clams create distinct “shlooping” sounds while digging into the tideline.
Sounds also arise from the expulsion of water, a necessary function for clams. When a clam rapidly contracts its adductor muscles to close its shells, it can forcefully eject water. This action generates a squirting or gurgling noise. Scallops, related bivalves, produce a sharp “crack” followed by a puffing sound when they quickly contract their shells to expel water or waste.
These sounds are largely imperceptible to the unaided human ear. Clam-generated noises are low-frequency, falling outside the human hearing range (20 to 20,000 Hertz). Specialized underwater microphones, known as hydrophones, are necessary to record and analyze these subtle acoustic signals. This equipment allows researchers to pick up the quiet clicks and squirts that characterize clam sound production.
The Role of Clam Sounds in Their Environment
The sounds clams make are incidental to their life processes within their aquatic surroundings. Burrowing, for example, is a primary activity for many clam species, providing protection from predators and currents while enabling access to food. The noises produced during this digging are a consequence of their physical interaction with the sediment. Similarly, sounds from expelling water or closing shells are mechanical outcomes of essential actions like feeding or self-defense.
While clams do not use sound for complex communication like some marine mammals, their acoustic output contributes to the overall underwater soundscape. These incidental noises become part of the ocean’s background hum. Other marine organisms may perceive these sounds, even if not directly from clams. For instance, some clam species, such as Donax variabilis, respond to low-frequency wave sounds, using them as cues to migrate with the tides.
Sounds produced by clams, or by predators interacting with them, can also have ecological significance. Oysters, another bivalve, close their shells in response to low-frequency sounds, a potential self-defense mechanism against threats. Conversely, the “shell-crushing” sounds made by predators like eagle rays when consuming mollusks are acoustic signals that can be detected and studied by scientists, providing insights into feeding behaviors.