Leopard shark finds electric dipole, attacks it as if it was prey buried under the sand ©Ivan Gonzalez.
Sharks and rays use their electric sense to detect prey buried under the sand. This picture was taken years ago during a high-school project I mentored as a graduate student at Scripps Institution of Oceanography. Conor McClune built this platform over a calibrated electric dipole, with a precise DC electric current simulating prey. The concentric rings are to give us a visual idea of the shark’s range of detection. We measured the distance from the dipole source when the leopard shark turns sharply and attacks the electric dipole source in the central ring, calculating the value of the electric field strength detected at the onset of the attack. Similar experiments gave the astonishing value of 5 nV/cm. That means that sharks can sense voltage differences of 0.000000005 Volts over two pores located a centimeter apart on their skin!