Orca (Orcinus orca)
Orcas, also known as killer whales, are the largest and most powerful dolphins. They roam the sea in packs of up to 40 animals, hunting seals, fishes, birds, porpoises, and other dolphins. They keep in touch through a complex sound system called echolocation. The animal can tell how far away an object is by how much time it takes for the sounds it emits to travel back.