Every living thing gives off a weak electrical field. Sharks can sense this with a series of pores—called the ampullae of Lorenzini—on their heads and around their eyes, and some species rely on this electrosensory ability to find food buried in the seafloor. (See pictures of electroreceptive fish.)

Two previous studies on the spotted catshark (Scyliorhinus canicula) and the clearnose skate (Raja eglanteria)—a relative of sharks—found similar freezing behavior in their young. But new research by shark biologist and doctoral student Ryan Kempster at the University of Western Australia has given scientists a more thorough understanding of this behavior.

It all started because Kempster wanted to build a better shark repellent. Since he needed to know how sharks