Why is an Orca also referred to as Killer Whale?
Ocra are also referred to as killer whales due to their way of life and feeding habits. They normally hunt marine animals and specialize in various kinds of preys. Learn more from http://science.howstuffworks.com/zoology/marine-life/orca-killer-whale.htm.
it is a nick name it got for killing, and also being a whale :P
Cuz it's a killing whale. They hunt large mammals vs eating tiny krill.