looser
November 6th, 2003, 9:08:23 AM
http://www.newscientist.com/news/news.jsp?id=ns99994343
Biologists have linked a mysterious, underwater farting sound to bubbles coming out of a herring's anus. No fish had been known to emit sound from its anus nor to be capable of producing such a high-pitched noise.
"It sounds just like a high-pitched raspberry," says Ben Wilson of the University of British Columbia in Vancouver, Canada (Listen here, .wav file). Wilson and his colleagues cannot be sure why herring make this sound, but initial research suggests that it might explain the puzzle of how shoals keep together after dark......
The biologists initially assumed that the swim bladder was also producing the high-pitched sound they had detected. But then they noticed that a stream of bubbles expelled from the fish's anus corresponded exactly with the timing of the noise. So a more likely cause was air escaping from the swim bladder through the anus.
It was at this point that the team named the noise Fast Repetitive Tick (FRT). But Wilson points that, unlike a human fart, the sounds are probably not caused by digestive gases because the number of sounds does not change when the fish are fed.............
Finally, three observations persuaded the researchers that the FRT is most likely produced for communication. Firstly, when more herring are in a tank, the researchers record more FRTs per fish.
Secondly, the herring are only noisy after dark, indicating that the sounds might allow the fish to locate one another when they cannot be seen. Thirdly, the biologists know that herrings can hear sounds of this frequency, while most fish cannot. This would allow them to communicate by FRT without alerting predators to their presence.
Wilson emphasises that at present this idea is just a theory.
Biologists have linked a mysterious, underwater farting sound to bubbles coming out of a herring's anus. No fish had been known to emit sound from its anus nor to be capable of producing such a high-pitched noise.
"It sounds just like a high-pitched raspberry," says Ben Wilson of the University of British Columbia in Vancouver, Canada (Listen here, .wav file). Wilson and his colleagues cannot be sure why herring make this sound, but initial research suggests that it might explain the puzzle of how shoals keep together after dark......
The biologists initially assumed that the swim bladder was also producing the high-pitched sound they had detected. But then they noticed that a stream of bubbles expelled from the fish's anus corresponded exactly with the timing of the noise. So a more likely cause was air escaping from the swim bladder through the anus.
It was at this point that the team named the noise Fast Repetitive Tick (FRT). But Wilson points that, unlike a human fart, the sounds are probably not caused by digestive gases because the number of sounds does not change when the fish are fed.............
Finally, three observations persuaded the researchers that the FRT is most likely produced for communication. Firstly, when more herring are in a tank, the researchers record more FRTs per fish.
Secondly, the herring are only noisy after dark, indicating that the sounds might allow the fish to locate one another when they cannot be seen. Thirdly, the biologists know that herrings can hear sounds of this frequency, while most fish cannot. This would allow them to communicate by FRT without alerting predators to their presence.
Wilson emphasises that at present this idea is just a theory.