Dolphins don't have just sonar at their disposal, scientists from the University of Hamburg discovered. Some dolphins can also detect the electric fields produced by living organisms. Rows of tiny holes along the nose of Guiana dolphins can detect electricity, possibly helping them find prey in murky water. Sharks and rays use electric fields to track their prey, but only a few mammals, including the platypus, share the ability. The Guiana dolphin is ten times more sensitive than a platypus, but likely a million times less sensitive than a shark.