🐾 Animals

Herring Farts: How Fish Talk With Bubbles

Herring don't just swim in silent schools – at night they chatter to one another by releasing tiny streams of bubbles from their rear ends. Scientists call it one of the strangest known examples of animal communication.

The Fish That Communicate With Farts

In the early 2000s two research teams, one in Canada and one in Scotland, independently discovered that herring produce high-pitched sounds by expelling air from their anal ducts. Working separately, both groups recorded schools of captive herring in darkened tanks and noticed rhythmic pulses of noise that rose whenever the fish were crowded together. Video and hydrophone recordings confirmed that each burst of sound coincided with a stream of bubbles escaping near the tail. Because the noise resembled a rapid raspberry and came from the same anatomical region as a fart, the phenomenon quickly captured public imagination. The discovery was remarkable because it identified a completely new mechanism of sound production in fish, one that had gone unnoticed despite herring being among the most studied and commercially important species on Earth.

Fast Repetitive Ticks Explained

The scientists named the sounds Fast Repetitive Ticks, abbreviated – with obvious delight – as FRTs. Each FRT is a burst of between seven and sixty-five pulses lasting up to several seconds, with a characteristic frequency ranging from roughly 1.7 to 22 kilohertz. Crucially, the bubbles are not digestive gas. Herring gulp air at the surface and store it in their swim bladder, an internal gas-filled organ that controls buoyancy. When they release a measured amount of that air through a duct near the anus, it produces the ticking sound. This means the herring is not passing waste gas at all but venting swallowed air on purpose. The rate of FRT production increases with the number of fish present, suggesting the behaviour is social rather than merely a by-product of digestion or pressure regulation.

Why Herring Bubble in the Dark

The leading hypothesis is that FRTs help herring stay together as a school after nightfall, when vision is useless. Herring can hear frequencies far above the range most predators detect, so a high-pitched bubble signal offers a private channel to keep neighbours located without alerting hunters such as seals or dolphins. Experiments showed that FRT rates climbed sharply in darkness and with higher fish density, exactly what you would expect from a contact call used to maintain group cohesion. Schooling is a herring's main defence against predators, so any mechanism that preserves the school through the night carries a real survival advantage. The behaviour may also relate to swim-bladder pressure management, but the strong link to social density points firmly toward communication as the primary function.

Cold War Bubbles and an Ig Nobel Prize

The herring fart has a curious military footnote. During the Cold War, the Swedish navy repeatedly detected mysterious underwater sounds near its coast and suspected intruding Soviet submarines, triggering costly hunts. Years later, acoustics researcher Magnus Wahlberg helped show that at least some of these phantom signals were consistent with the bubble sounds of vast herring shoals rather than enemy vessels – a diplomatic and scientific plot twist. In 2004 the two herring research teams jointly received the Ig Nobel Prize in Biology, an award celebrating research that first makes people laugh and then makes them think. Far from being a mere joke, the work opened a serious new field in bioacoustics and reminded biologists that even the most familiar animals can still hide astonishing secrets.

Did You Know?

Fun Fact

Researchers noticed that the more herring they put in a tank, the more the fish farted – which is exactly how they proved the bubbles were a way of chatting rather than just letting off gas.

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