Science - November 27, 2014

Cuttlefish may listen out for enemies

Text:
Rob Ramaker

The cuttlefish, a member of the Cephalopod class which inhabits Dutch coastal waters, appears to have good hearing.

It is thought that it may hear its enemies approaching. These findings came out of sound tests carried out by Wageningen biology student Julia Samson. She writes about it in the Journal of Experimental Biology.

  • Test shows that cuttlefish register sounds.
  • Effect noisy shipping not yet known

‘We did not know beforehand whether they would react,’ says Samson from the United States, where she is now in graduate school. There were indications that cuttlefish can hear, but Samson is the first to have researched that systematically. ‘Now we know that they react to sound and very strongly too, to some noises.’ The biologist released the roughly 20 centimetre-long cuttlefish into small basins. There they were exposed to a tone for three seconds and their reaction was filmed. At the tested wavelengths - between 80 and 1000 Hertz, a range within which we hear well too  - she saw clear changes. At a moderate volume the creatures changed colour, and at a loud volume they even squirted ink and swam away. With the speakers she was using Samson could not test whether the cuttlefish react to ultrasound, as dolphins do. ‘So we don’t know whether cuttlefish  pick that up,’ says Samson. ‘Those are two very different kinds of sound.’ 

NORTH SEA

Given that cuttlefish almost certainly do not produce any noise, they probably do not use their hearing for communication. Samson’s guess is that the creatures listen out for predators. That would explain why they react so defensively by spouting ink, for example, or camouflaging themselves. There has been a lot of interest in recent years in ‘noise pollution’ in the sea. The noise of ships, for instance, disturbs communication among porpoises and dolphins. This discussion is certainly relevant to the Netherlands, since our North Sea coast is one of the busiest shipping channels in the world. It also houses about 100 wind turbines and a large number of oil rigs. Samson’s results suggest than non-mammals might suffer from intrusive noise too. At the same time as she was doing her research, another group showed that cuttlefish may hear ships, but Samson thinks it is too soon to draw conclusions from this. 

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