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Thursday, July 28, 2011

South American dolphin is the first 'true mammal' to sense prey by their electric fields

By Daily Mail Reporter

South American dolphins can sense their prey by using electric fields, new research suggests.

The study shows that the dolphins are the first 'true mammal' to do this.

Electro-reception is well known in fish and amphibians, but it was previously thought the only mammal to do this was the platypus.

Guiana dolphins can sense electrical signals to hunt for food

Writing in the Royal Society's journal Proceedings B, researchers also predict that cetaceans may show the same ability.

The Guiana dolphin (Sotalia guianensis) lives around the east coast of South America, and resembles more common bottlenose dolphin.

Like all of the toothed cetaceans, it hunts and locates using sound.

But scientists have now shown that at close range, it can also sense electrical signals.

They are not as sensitive as sharks and rays, but can detect signals of the same size as those produced in water when fish move their muscles.

Project leader Wolf Hanke from the University of Rostock, Germany, told the BBC: 'It feeds in the bottom [of the sea] a lot, and it lives in water where there can be a lot of silt and mud suspended.

'And echolocation doesn't work at very close range, so this is where electrolocation would come in.'

Captive Guiana dolphins have been kept at the zoo in Muenster, in Germany where researchers were trying to find out the function of small depressions in the dolphin's rostrum.

They trained one of the dolphins to put its head on a 'rest station', where electrodes delivered a tiny electrical signal into the water.

When a signal was present, the dolphin received a reward if it swam away; if not, it received a reward for staying put.

Then a plastic shield was placed above the lines of crypts, blocking any electrical sensing and it remained still throughout.



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