The orca or killer whale is a toothed whale that is an efficient predator, even attacking huge young blue whales. Their only enemy is human beings. Orcas grow to be about 27-33 feet (8-10 m) long, weighing more than 8,000-12,000 pounds (3.600-5.400 kg). The male orca is larger than the female. They are the largest member of the dolphin family. Orcas whales live in waters ranging from tropical to arctic, and both coastal and deep oceanic waters. They are found in all the world's oceans and most of the seas. Orcas sometimes enter estuaries, but don't go far from the sea.