By Ben Gruber

MIAMI (Reuters) - Experiments at Vanderbilt University have proven a 200-year-old observation that electric eels can leap out of water and shock animals to death, a claim originally made by 19th century biologist and explorer Alexander von Humboldt.

During a field trip to the Amazon basin in 1800, Humboldt said he saw electric eels leaping out of the water and delivering enough voltage to kill a horse. But with no scientific studies on the matter, and no similar observations since, many had come to believe that the famous naturalist was exaggerating. 

"The first time I read von Humboldt's tale, I thought it was completely bizarre," said Ken Catania, the Stevenson Professor of Biological Sciences at Vanderbilt University, in Nashville, Tennessee, where the recent experiments were conducted. "Why would the eels attack the horses instead of swimming away?"

The answer, according to Catania, is that the eels felt cornered and threatened. A biologist who has been studying eels for several years, Catania said he not only validated the original account but found evidence that leaping eels were far more terrifying than even von Humboldt realized.

When an eel is submerged, the power of its electrical pulses is distributed throughout the water, freezing its target into state of shock, he said. Out of water, the high voltage electrical salvo zaps a target directly through the skin near the eel's chin, intensifying the effect.  

To visualize it, Catania covered a plastic arm and crocodile head with a conductive metal strip and a network of light-emitting diodes (LEDs), which used the voltage supplied by the eels and lit up brightly when attacked. 

     "When you see the LEDs light up, think of them as the endings of pain nerves being stimulated. That will give you an idea of how effective these attacks can be," Catania said.

The research was funded by the National Science Foundation and the findings were published in the Proceedings of the National Academy of Sciences this week. 

(Reporting by Ben Gruber; Editing by Bill Rigby)