Dolphins: they have an electric sensor.

They are equipped with sensors that, like radar, are capable of echolocation. But that's not all. To locate their prey, it has been discovered that some dolphin species, those of the Sotalis species, to which our tucuxi dolphin belongs, also use an even more refined technique. These animals, widespread along the entire coast of South America, from the Guianas to the Brazilian Northeast, can distinguish, at short distances, the electric field of small animals on which they feed thanks to special electro-sensory organs located on the sides of their heads. The discovery was made by researchers at the University of Rostock, Germany. The most likely hypothesis is that these cetaceans have developed this ability to hunt in the often murky and muddy waters of the region where they live. Until now, such electroreceptive capabilities had only been detected in some fish, such as sharks, and in the platypus, a very strange mammal from Australia that reproduces by laying eggs. This is the first time that such organs have been found in "real" mammals. It is suspected that other cetaceans, such as sperm whales, are also endowed with this ability. Sperm whales, the largest toothed mammals in the world, are capable of hunting their main prey, giant squid, in ocean depths reaching 3 meters.