This is a video of an electric eel sending out electric pulses to paralyze its prey — and then devouring its live, helpless body. The sounds you hear are the electric pulses:
The video is part of new research published today in Science showing, for the first time, how electric eels' shocks actually incapacitate their prey. Kenneth Catania, of Vanderbilt University, found that eels' electric discharge can paralyze fish's muscles, making them easy bait.
Catania also discovered that eels use an entirely different type of jolt to find fish in the first place. The eels — who have poor eyesight and often live in murky water — first send out an electric signal that make other fish twitch, making them easier to find. After that, the eels make other pulses to paralyze their prey.
Eels can also use their electric organs for something far more benign — navigation.
Catania performed his research by putting eels in a big laboratory tank with fish. Presumably he was careful not to put his bare hands in: a large electric eel can shock at up to 600 volts — five times the voltage of an electric socket.