Bizarre But True! The Swedish Navy spent fifteen years tracking what they were certain was Russian submarines infiltrating their waters. They weren’t wrong about the sounds. They were wrong about the source. It was herring. Farting…
The Military Heard “Acts Of War” – Scientists Heard Fish
In the early 1980s, Swedish naval forces detected mysterious underwater sounds near secret military bases along their coastline. The pattern repeated. The frequency matched submarine activity. Military analysts flagged it as an invasion – potentially the opening salvos of nuclear conflict.
Magnus Wahlberg, brought in to investigate, described the sounds differently: like someone frying bacon. Or small air bubbles releasing underwater.
After fifteen years of investigation, the Navy discovered the truth. The “typical sound” they’d been tracking was flatulence from Atlantic herring.
FRTs Are Real (And They Won Scientists A Nobel Prize)
Researchers didn’t just discover fish farts. They categorised them. The technical term: Fast Repetitive Tick sounds – FRTs for short.
These pulses range from 1.7 to 22 kHz, lasting between 0.6 and 7.6 seconds. Robert Batty, Ben Wilson and Larry Dill studied Pacific and Atlantic herring across Canada and Scotland, documenting the phenomenon in detail.
The discovery earned them an Ig Nobel Prize, an award honouring achievements that first make people laugh, then make them think.
They’re Not Actually Farts (Which Makes It Stranger)
Here’s where it gets more bizarre.
Herring don’t produce these sounds from gut gas. They swallow air from the surface, store it in their swim bladders, then expel it through a duct connected to an opening near their anuses.
Robert Batty confirmed: “The evidence suggests it’s not gut gas that’s responsible. If you starve the fish, they still produce this sound.” Magnus Wahlberg explained that herring have a swim bladder connected to the anal duct – a very unique connection, only found in herring.
So technically, they’re not farts. But the sound? Batty described it perfectly: “high-pitched raspberries.”
Sharks Can’t Hear Them But Killer Whales Can
The frequency of most FRTs sits above 2 kHz, outside the known auditory range of most predatory fish.
Sharks can’t hear herring farts. But marine mammals can. Seals, walruses, dolphins and killer whales all pick up the sounds. Robert Batty noted the problem: “There are pods of killer whales that specialise in feeding on herring. The fear is they won’t be able to pick up the sounds the herring are making” if noise pollution interferes.
Herring evolved a communication system their main predators can’t detect — but accidentally made themselves audible to the ones that matter most.
Fishermen Knew Before Scientists Did
Local Swedish fishermen told researchers their nets sometimes “boiled” from the bubbles.
There’s a belief amongst fishermen that herring, when caught, articulate a sound similar to the word “cheese.” Some say herrings “sneeze” – an observation Aristotle made about gurnards centuries ago. The data just confirmed what people on boats already suspected.
The More Crowded, The Louder The Conversation
Researchers recorded that the higher the concentration of herring in one place, the more pulse sounds an individual fish produced.
Atlantic herring travel in schools of up to four cubic kilometres. Imagine the noise. The Swedish Navy wasn’t tracking one submarine. They were tracking billions of fish having a conversation in the dark using a biological mechanism so specific, so bizarre, that it took fifteen years and multiple scientific teams to decode. Just be grateful that nobody pushed the ‘big red button’ as s result of it…!
