The oceans of the world are teeming with life. From the cold Arctic seas to the warm waters of the tropics, the number and variety of species that live in the world's oceans boggles the mind.

Since we live on land, humans are often unaware of the constant life-and-death battles waged below the waves. Complex food chains exist in the oceans with microscopic algae and plankton at the bottom and the world's largest fishes and aquatic mammals at the top.

In fact, the oceans are home to perhaps the most fierce apex predator on Earth. It's a killing machine with no natural predators that feeds on most anything that comes across its path, including fish, sea birds, seals, and even whales and sharks. If you've ever seen an awesome black-and-white beast with long, sharp teeth, then you already know what we're talking about: killer whales!

Killer whales are also known as orcas, a name that comes from their scientific name: Orcinus orca. Although they're not considered a danger to humans in the wild, killer whales will eat just about anything else that crosses their path.

They have a huge range, living anywhere from the Arctic to tropical waters near the equator. In addition to fish, killer whales will hunt other animals in coastal waters, such as seals and sea birds. They're also not afraid to take on the other large creatures they share the oceans with, including squid, octopuses, sea turtles, sharks, and other whales.

The tendency to take on other whales is where their terrifying name comes from. Long ago, sailors referred to these massive creatures as "whale killers." Eventually that nickname changed to killer whale. In Spanish, they're referred to as ballena asesina, which means "assassin whale."

The name killer whale is still a bit deceptive, though. Scientifically, they're classified as a toothed whale that's actually a member of the dolphin family (Delphinidae). They're the largest member of the oceanic dolphin family, which also includes dolphins and pilot whales.

Killer whales rule the sea thanks to their impressive physical characteristics. They can grow to be nearly as long as a school bus and weigh up to 12,000 pounds. They also possess a mouth full of sharp teeth that can grow to be four inches long.

Killer whales are very social animals that live in groups called pods. Pods can have as many as 40 members that stick together to hunt for food. Like the dolphins they're related to, killer whales use echolocation to communicate with each other.

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