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Thursday, 16 May, 2002, 09:54 GMT 10:54 UK
Alligator's sensitive side
Alligator (Crocodilian.com)
Alligators can detect the slightest ripple in the water
Scientists have explained the extra-sensory powers of alligators and crocodiles.

The animals can hunt without sight, sound or smell using sensors on their jaws that detect ripples in the water.


This sensory organ may have appeared around 200 million years ago, in the Jurassic period

Daphne Soares, University of Maryland
The reptiles lurk half submerged at night, waiting for a potential snack.

When prey enters the water, perhaps to take a drink, the alligator or crocodile is able to sense even the slightest movement and pounce.

Even a single droplet falling into a tank the size of a bath can be sensed by the network of pressure detectors on the creatures' jaws.

Jurassic beginnings

The sensors, about the size of a pinhead, are dotted around the animal's face like a beard.

Alligator jaw (Crocodilian.com)
The bumps are dotted around the jaws like a beard
The marks look like tiny pinpricks. Alligator and crocodile experts have noticed them before but have not been able to fully explain the marks.

All living alligators and crocodiles have the small holes, as do some of the family's fossil ancestors.

The biologist behind the latest research, Daphne Soares, thinks the sensory system evolved millions of years ago, when primitive crocodiles shared the Earth with dinosaurs.

"Evidence shows that this sensory organ may have appeared around 200 million years ago, in the Jurassic period," says the University of Maryland scientist.

"It's fun to imagine these enormous extinct crocodiles sitting half way submerged in the water at night, waiting for dinosaurs to come and drink.

"Just at the moment the dinosaur broke the water surface with its mouth, it would have sent pressure waves in the water, telling the crocodile where to get its next meal."

Ms Soares has named the sensors dome pressure receptors.

In the dark

They only work when the animals are half under the water.

Lab experiments show that alligators can still sense water disturbances when their eyes, ears and noses are covered.

When the bumps are covered with a layer of plastic jelly, the alligators are unaware of any movements in the water.

The alligator research is published in the journal Nature.

Images courtesy of crocodilian.com.

See also:

21 Nov 01 | Sci/Tech
Breathing like dinosaurs
25 Oct 01 | Sci/Tech
Giant crocodile was length of bus
23 Jun 00 | Sci/Tech
Chicago learns from crocodile rock
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